Blind, Blind-Deaf and Partially Blind Dog Behaviors, Biology and Origins
by Dr Eisenhosen (pen name of a modern PhD), February 11, 2011; updated October 2012
Summary
Summary: Blindness strongly influences the behaviors of dogs but almost never[1] does becoming blind or deaf cause a dog to become aggressive or indeed usually much change its temperament and personality. With consistent attention and education by their humans, blind dogs can adapt to live in homes with people and other dogs, etc. Most dogs adapt well if their humans work with them to make it possible. While the dogs adapt by shifting to relying on smells and sounds in place of sight, their people can label indoors objects with smells and permit the dogs to bark when they need to do that to “see” their places with their ears or other dog-detectors of vibration-sounds. Physically and biologically reliable owners’ anecdotes of the behaviors of blind dogs (and their people) help to understand how the main features of dog-blindness change a dog’s behavior.
To some extent “non-standard not caused by physical blows or wounds” vision loss and blindness often goes along with (correlates with) inherited genetic deafness and geriatric (old age) loss of vision and hearing. A few comparisons to humans were made. This paper tried to offer a readable insight to blind dog behaviors, basics of their loss of vision and a little on the genetic origins of some blindness.
Behaviors: Individual dogs with their people and perhaps with other dogs and cats find or create an astonishing variety of ways to adapt their mutual behaviors to live happily and usefully together. We illustrate that with anecdotes of real events, dogs and people. Also we venture a few speculations about behaviors and certain eye features.
Summary: Blindness strongly influences the behaviors of dogs but almost never[1] does becoming blind or deaf cause a dog to become aggressive or indeed usually much change its temperament and personality. With consistent attention and education by their humans, blind dogs can adapt to live in homes with people and other dogs, etc. Most dogs adapt well if their humans work with them to make it possible. While the dogs adapt by shifting to relying on smells and sounds in place of sight, their people can label indoors objects with smells and permit the dogs to bark when they need to do that to “see” their places with their ears or other dog-detectors of vibration-sounds. Physically and biologically reliable owners’ anecdotes of the behaviors of blind dogs (and their people) help to understand how the main features of dog-blindness change a dog’s behavior.
To some extent “non-standard not caused by physical blows or wounds” vision loss and blindness often goes along with (correlates with) inherited genetic deafness and geriatric (old age) loss of vision and hearing. A few comparisons to humans were made. This paper tried to offer a readable insight to blind dog behaviors, basics of their loss of vision and a little on the genetic origins of some blindness.
Behaviors: Individual dogs with their people and perhaps with other dogs and cats find or create an astonishing variety of ways to adapt their mutual behaviors to live happily and usefully together. We illustrate that with anecdotes of real events, dogs and people. Also we venture a few speculations about behaviors and certain eye features.
Biology and Physics: A sketch of a dog’s eye, Figure 1.
An ordinary dog’s eye has the same major parts as human eyes, excepting that most dogs also have: 1) a reflective layer called a tapetum behind their retina, to enhance seeing in dim light and 2) biology nerve connections for superior detection of movements in the images.
Genetics, diseases, accidents and old-age can damage the components of dogs’ eyes and nervous systems. Dr S. Coren [3] reported that old age pains and disabilities can make some dogs (and probably persons) bad tempered, unable to move quickly when in danger, and difficult to live with for other dogs, cats and humans. Deafness and blindness were almost never the direct causes of those unsocial behaviors.
Origins: As of 2010 it seemed that the differences of canine vision and human vision were “accidental” genetic adaptations to very different original environments and life-styles, before the proto-canines emerged in North America and proto-humans ancestors emerged in Africa - well over 15,000 years ago. Ref. A. Miklosi [2] and others[1, etc]: Probably dogs co-evolved with “modern” humans after humans began farming, following the ice age about 12,000 years before the present. Biological data from many species suggested that Always, a few of the dogs and humans in every generation, from the beginning, were born deaf, blind or deaf and blind. Many of those dogs were probably almost entirely white, or spotted, or owned “flashy” coats.
Introduction
Gotta be able to find the toilet door, and let the folks know when to open it. Smells can still be “read” by blind dogs and the places recalled, for getting around without rudely bumping into other dogs, people and the furniture. Can’t “read” the newspapers so well any more, or not at all. Never could spot the apricot colored toys on the brown rug, so that wasn’t a loss. IF the ears still work, the dog can learn to pretend it’s a bat or dolphin, or a Navy SONAR set and “see” things and distances by “reading” the echoes of sharp barks or noise vibrations. And if the usual inner ears quit working, or never did work right, dogs are born with about eight or nine other natural body biological ways to detect vibration-sounds for analysis by their brains, to communicate and navigate. A slightly desperate, possible socially risky way for newly blind of finding where things such as other dogs are, is to gently bump into them - - as all puppies do when they are about four weeks old and have no idea about socially proper behavior with adult dogs (who hate to be rudely bumped against or jumped upon.) Of course, at first when a blind (of deaf) dog bumps into its personal human, the dog likely will stay cuddled safely as close as possible “forever” or until the human takes a bath or goes out shopping (this sort of doggish action is often called “velcroing” because the dog sticks to the person like Velcro.)
A separate but connected set of dog-social challenges must be settled acceptably by each blind dog, even if the solutions amaze and puzzle the humans. Human supervision and counseling is important, just as though a dozen kindergarten kids were suddenly placed together in a play-ground to have fun without maiming each other. New ways of socializing with other dogs must be learned because a blind dog can’t see another dog’s “I’m friendly” body signals, and a deaf dog can’t hear another dog’s vocal invitation to play, or stay away.
Most adult dogs consider staring at them is rude because that might signal an adult dog that stares (except Border Collies) is deciding whether to grab the other dog. Various reports indicate that some blind dogs take advantage of being immune to the staring-games of others, such as Border Collies. But at dog parks a few anxious ordinary dogs reportedly give up waiting for the blind dog to attack and so launch a pre-emptive strike – which badly surprises the blind dog.
A likewise socially unexpected event to a stranger adult dog is meeting a blind dog who deliberately (like a poorly educated delinquent puppy-juvenile) bumps into the stranger. Some adult dogs (especially females who raised many puppies) are inclined to abruptly set about teaching a bumping dog to behave properly, without crashing carelessly into other adult dogs or people. However, some blind dogs when playing are remarkably casual and uncaring about bumping into furniture, etc as long as no blood gets shed.
Indoors and outdoors social walk-abouts are desirable while on a short leash, or even carried with their humans, so that the dogs can discover where everything is, and where they are. Scents used as labels by the humans are a sure help for that.
A large part of the social challenges for a blind, deaf, blind-deaf dog, ordinary dogs and any cats it associates with and their humans was called by Alexandra Semyonova (see reference) “linguistic consensus” and non-aggression dog-rules - namely agreeing on a set of signals that mean each of them is friendly and expects the other (regardless of how odd it seems) to be polite and never intentionally cause serious pain or wounds. Basically, everyone on the playground gets to have their turn in the fun, and nobody gets hurt on purpose. Many observations confirmed that if they can agree that they are each polite, if there is a mistake the antics will abruptly cease and probably the delinquent will appear to be repentant, regretting an error – despite whatever it was maybe being uncertain to the offender. Delinquents get ostracized-ignored and nobody plays with them, or even more remarkable occasionally the rest of the puppies form a “mob” like soccer players and thrash the delinquent.
I. Behaviors of some Blind Dogs
Blindness behaviors can be puzzling to people only used to ordinary dogs. Observations by a reliable observer were followed by comments. The observations of Shep were a welcome test to see if the research pieces ‘fit together’, without lots of behaviors left to be figured out later.
----- Original Message - Observations -----
My Shep has LOUSY eye sight, very skew-wiff (drooping), I have a pic of his eyes, the vet tells me the muscles in the eye to hold his eyes in normal position, the lower muscle is too tight & the top of the eye muscles are too loose, so his eyes are not correctly positioned, but other than that, Shep does not see well. He also has badly misshapen pupils -- all from the MERLE gene, father a red merle, mother a blue merle koolis X blue cattle dog & deafness from the merle & cattle dog genes, BUT a stunning merle coat.
I noticed that some colours BLEND with him e.g. we have a rubber Frisbee (disc) of a dull deep orange/apricot colour & when inside he cannot see this against our brown wooden floors, yet he can see it against green grass or DIRT.
Also, Shep cannot do jumps in (competition) agility because he does not see the jump bar --- white with blue tape in stripes along the bar - he cannot see this against grass. BUT he can see it with a background of white cement -- we played with this at home and he jumps like a beauty.
We use LARGER toys to play with Shep, as he cannot follow a tennis ball when thrown a distance or fast, BUT he can see it, if lobbed slowly close to him in the air and then he is a bullet going up to pluck it out of the air. I feel he has lousy distance vision and just okay close vision.
Shep can see 'glo' in the dark toys to play games, we have found he does not see well in bright sunshine, but sees much better at dusk & dawn & overcast skies, (and best in moonlight), BUT he cannot see - goes blind virtually - in dappled light under trees e.g. light filtered by leaves, but not fully shade & not full sunlight.
I would not say dogs cannot see colours, but I do not think humans actually KNOW how dogs see fully, or by what level of colour. I think dogs rely on movement and see that amazingly well.
&&& &&&
Comments from recent research and analysis were used to offer estimates based on Shep's described behavior and on published research on dogs and humans. I suspect that Shep's behavior demonstrated that he had several understandable oddities of his vision - compared to most other ordinary dogs and most humans.
My first reaction from Shep's sensitivity to sunlight is to suggest that Shep's eye "rod" sensor cells of his retina are incredibly more sensitive than his "cone" retina cells, and maybe more sensitive than those of ordinary dogs. Cone cells in humans eyes are the main color detectors and human rod cells were believed to Not be useful for color detection. Dogs tested in 1989 were using their rod-cells also as their brightness of grays detectors.
About the jump-bar, I first suggested that like certain humans Shep [me, sometimes] sees Bleen or Grue {a joke about people who can't see blue distinguishably from green. In the Welsh language, a single word designated all shades of color from green thru blue. Also, in humans who lived for a long time in the Mohave Desert of the US, for persons who almost never used sunglasses, the extreme ultraviolet (UV) light destroyed their ability to distinguish pale greens from pale blues.} Our computer simulations in fact suggest that Shep might entirely lack the ability to distinguish colors, because possibly (probably?) genetically he lacks useful cone cells, and must see entirely with his rod cells that only see shades of grey (see Figure 2, 3 and 4).
If his reflected light eye-color was reddish, he probably lacked the usual reflective layer in his eyes that helps dogs to see at night. Shep’s blue-green colored irises and pupils in daylight didn’t confirm or deny that he had a tapetum reflective layer. A rough guess from his ability to see a "Glo" ball at night is that he has a normal reflective layer just behind his retina.
Lousy distant vision is accountable because of odd shaped pupils; experiments on humans showed that their brains after a few days were able to see objects normally after they got used to wearing glasses that warped the "picture" as his distorted pupils do. Close in if he doesn't care about details, he would be able to see well enough, but way out at a distance he would fail to distinguish “small" fine features as well as ordinary dogs. A further problem for Shep would be that his odd pupils would make it impossible for him to effectively place vital far off small objects (such as those on the horizon) on his super-fine sharpness part of the retina, which is called the ‘visual streak.’
About his difficulty in "dappled" light - - my estimate was that Shep because of his pupils shapes was forced to rely mostly on his coarse rod detectors in the outer areas of his retinas, and unable to use his sharp-vision streak as ordinary long-muzzle dogs do. Which would also fit with being almost blinded by bright sunlight on his super-sensitive rod cells but seeing well in dim light (perhaps better than the other dogs?)
Geneticists estimated that such odd inherited vision and deafness traits came into existence before mammals did. But modern dog breeders by recent excessive inbreeding for fancy (marketable at high price!) flashy coats are concentrating the problem genes. Sadly, Dalmatians were a "poster child" dog breed that would cease to exist in their current form if the deafness/blindness/ blue-eyes genes were drastically reduced by zealous selective breeding against those traits.
[In response to the color chart] …That is amazing, it explains why Shep cannot see an orange-apricot Frisbee against brown flooring, it would BLEND on him. Yet he can see it against green grass and sky. Looking at the night vision, they have better light sensitivity for vision than us, how remarkable.
Bonding and educating their Startle Reflexes are the vital basis for helping blind dogs adapt to new homes, and learn to make full use of their biological natural abilities. Bonding is essentially the creation of complete mutual trust between the dog and its people. Providing regular good food, proper water available, plenty of safe secure exercise and mental exercise are necessary. Toilet training ought to be done with positive rewards and clear guidance to the dog about where and when things should be done. Advice of owners suggested that bonding and initial steps of education often needed about 30 days and some dogs suddenly responded after several months.
Usually a crate is very desirable to provide the dog a personal private place to be at night. They need to learn that when its new people leave the room and the house they will always come back again before the food and water run out, or something happens to the worried dog. Educating a blind or deaf dog’s startle reflex can be done by occasionally touching the dog gently, with treats in hand, and gentle words and petting, so that the dog concludes that new strange events are “good things” and good things are about to happen. A rescued dog may be anxious and insecure, with poor habits about the toilet and excessive guarding of food and toys, and maybe even its new people. The dog needs to learn that there is no reason for guarding food and other stuff that are reliable and not arbitrarily permanently taken away.
Scents mapping is a key method for blind dogs to keep track of where things are, find the door for the toilet, and generally get around without bumping into objects by accident. Most dogs even with ordinary sight and hearing make much use of observing the scents of nearby objects and places that they care about, and recall roughly where they are, so dogs born blind or who become blind can usually make prompt use of the scents to get around well. After getting discouraged by trying to figure out the chaotic aromas of the rescue places, of course a rescued dog must explore to learn the scents of a new home. We saw no proof that genetics or old age blindness or deafness cause losses of dogs’ ability to detect and make use of smells. However a loss or reduction of the ability to detect and analyze scents can happen to some dogs - - a person might want to verify that a dog’s nose is effective if their blind dog seemed unable to use smells.
Adapting for use of the natural ‘auxiliary’ biological additional "devices" of dogs that are means of detecting mechanical vibrations (sound): Succinctly, any dog that isn’t dead has many physical ways to detect the vibrations of sounds, analyze, and use the information. BAER tests only examine whether a dog can hear the same way as ordinary humans do. Certainly by 2004, scientists, as described by Dr S Coren, knew that dogs have many ways - - in addition to the exclusively inner-ear type of mechanical vibration detection (hearing) tested with the usual advertised BAER electronics wires in the head and ear-phones equipment. [See http://deafdogsforever.weebly.com, the adaptive hearing page.]
II. Biology and Physics of Dogs’ Eyes
Despite that they all have similar major eye parts; in details dogs’ eyes can differ from one breed to another, and differ in some key parts from ordinary humans eyes. Here the features of most common importance to blind dogs are discussed; with mention of only the most vital technical function and connections between key parts. Some breeds of dogs are near-sighted, i.e. unable to sharply focus their eyes for far away; other breeds exceeded many humans in distant vision (far-sighted or extra skilled vision.) A typical modern high quality digital camera has most of the same or equivalent parts and functions. Illustrative comparisons are made with cameras and human eyes.
Defects happen from injuries, diseases and from genetic causes. Certain genetic causes act mostly during the very earliest days of the formation of the embryos, although the consequences are usually noticed by humans perhaps after about nine days (varies with Breeds) of the dogs’ age when their eyes open, or even later when behavior oddities are noticed. Some of the genes that cause difficulties have been identified, and seem to often overlap in causing defects in the dog’s hearing (one-ear or two-ears deafness). Collateral impacts of the genes seem to include blue eyes, and flashy coats such as double dapples, white great Danes, and spotted white dogs.
Many instances of blindness were caused by glaucoma, diabetes, SARs or PRA. The genetic causes of the losses of nerve structures of SARs and PRA were reported in research reports to closely resemble the process of deterioration of deafness-nervous systems, and likewise in those situations involved melanin. SARs and PRA occurred mostly in older ages of the dogs impacted.
Old age for some dogs means ‘geriatric blindness’ including cataracts, often with increasing deafness, loss of cognitive functions and arthritis, etc. S Coren described various ways to minimize and delay the difficulties of old age.
Of course accidents such as car crashes, and exposures to chemicals can cause blindness and partial loss or difficulties of vision.
Lenses-cornea: Focusing for near or far sight, each eye's transparent lens is flexible so that muscles can contact or relax to focus the vision images sharply on the active cells of the retina Huskys’[1] Corneas are the protection against damage (comparable to the clear crystal over a watch face). Corneas are transparent front covers of the lenses. The corneas are kept moist and occasionally cleaned and covered by the eye-lids.
If a lens becomes off-color, hazy or cloudy-“milky” (translucent) the lens becomes warmer by absorbing light energy, which tends to stiffen it. Less light remains to reach the retina (so the light seems dimmer to the dog), and the light is typically scattered over many retina cells instead of sharply on the best cells for a sharp image (so the dog’s vision blurs, as a human would feel looking through dense fog) as a lens became more cloudy or milky. Old age is a common factor of cloudy lenses.
Different colors focus at different distances behind the lenses, so in theory retinas could be structured in color sensitive layers with the red sensitive layer closest to the lens, like old camera color film. Dogs’ retinas are more like a television or computer monitor screens with individual color detectors next to each other in roughly a single layer.
A common difficulty of lenses with age is their getting stiffer and failing to focus images over the entire range of distances needed. It seems unlikely that a dog would want to focus sharply on anything closer than the end of its nose; so the distance defining “near-sighted” is the length of the dog’s muzzle. Several breeds were studied in a project where the estimated minimum focus distance was about 15 inches (slightly far-sighted). A slightly far-sighted capability for sharp vision would shift the dog's detection apparatus possibly mainly to nose-odor smells at ranges where its nose is most effective for locating things, and deciding what can or should be done (such as eat it?) People rarely object or perhaps rarely notice their dog is near-sighted, or perhaps far-sighted. Eye-glasses “doggles” could correct such difficulties.
Iris, Pupil and Neurology Processes: The outer visible colored area around the usually black pupil is called the “iris.” Changes that shape the pupil are the vital feature in the inner edge of the iris. If the eye is spherical, generally the pupil ought to be round at all sizes of the openings in the iris. Probably an elliptical pupil is compatible with an almond shaped eye. For ordinary dogs, the pupil is widest under dim light and becomes very much smaller in bright light.
The area of the pupil controls the amount of distance from the eye that is in sharp focus. With tiny pupils (in bright light) the distance range of sharpness is maximum. In dim light, with the pupil wider open, the range of sharp focus becomes very short, and in those situations the health and adjustability of the eye’s lens becomes most important. Dim light outdoors of course is most likely to be encountered during sunrise, sunset-twilight, at night and under dense vegetation. It would be no surprise that ancestral feral canines tended to hunt big game in quite open terrain during daylight, and smaller game in near darkness and denser vegetation. Browsing[2] on fruit, grains and vegetation could be done relying mostly on scent-smells, at any time of day. An excellent sense of smell would reduce the need for excellent sensitivity to colors as experienced by humans, who typically (especially males) have limited odors detection abilities.
Control of the iris and pupil is probably done almost entirely with nerve-logic connections located with each eye, rather than relying entirely on back and forth signals traffic to processors in the brain. For example, the colors are seen by a comparison of signals from adjacent different types of cones. Detection by dogs of images movements are probably done with biological logic close behind the retina’s layer of rods and cones.
Oddities in the musculature operating an iris can cause the opening to be star-shaped, perhaps almost square, or vertical slits (in cats[3]), or sometimes simply “freeze” ceasing to change size. Consequences of odd shaped eye pupils seem to be mainly a drastic loss of sharpness-acuity, and especially a major loss of an ability to use their extremely high sharpness visual-streak (linear fovea). Misshapen pupils scatter the light rays of images over inappropriate (low resolution – poor sharpness) areas of its retina, which makes it difficult or impossible for such a dog to use its maximum sharpness visual streak in the way of ordinary dogs. So far as known to 2012, about all that can be done to relieve their difficulties is that a dog can try of its own initiative to discover that a special positioning of its head and eyes gets the best sharpness.
"Invisible bugs on the wall or flying in the sky" and other vision distractions that can become fatal: Incidentally, - about the possibility of dogs with bleeding in the eyes pawing at the eye (and some people report dogs staring at non-existent flying insects, or non-real insects on walls) - - such comparable behaviors can arise from what an ophthalmologist called "floaters" which are tiny bits of debris or tiny blood specks floating about in the fluid inside the eye-ball. They are most prominent against a light colored plain background, and might not be noticeable against a complex featured dark background such as is common outdoors.
Because the “flying” specks are inside the eyeball, the specks move with the dogs' eye movement and if the dog tries to catch one, the dog can die of whirling in circles instead of eating, etc. - as reported! The specks stay in one place if the dog stares, like a Border Collie tends to do, so that behavior is more typically reported among some breeds of deaf dogs. Usually ophthalmologist with human grade instruments can’t detect specific specks or debris floating about in the eye, so for humans the diagnosis is typically based on the victim's description, including age, conditions such as diabetes, alcoholism, certain chemical exposures, etc., including family history (genetics- same as dogs). How do I know about the behavior connections to that sort of eye-disorders? Easy - 30 years of personal experience!
Retina
In an old camera the film only functioned as an equivalent of the light detection cells of the retina (plus an image memory). Modern digital cameras have digital electronic light detectors and most of the functions equivalent to those of dogs’ eyes. In dogs’ eyes the retinas are where the images fall on the back inside surface of each eye, where the images are detected, partly analyzed locally, and then “coded” for quick transfer to the brain. The retina has a layer of light detector rods and cones, in front of a reflective layer that improves the use of dim light primarily by the color-vision cones, then a layer of biological logic neurons connecting between the light detectors and the ganglions and nerves that then transmit the encoded compressed signals to the brain for more analysis and action.
Scan rate - movement detection and “Movies”: Sensitivity of detecting movement experiments reported by S. Coren indicated that brain-processing of signals from their eyes permit some breeds of dogs to see moving objects as accurately as or better than most humans. However, unmoving objects are seen with coarser static biological logic. Most observed dogs were better able to detect movement than ordinary humans.
Accuracy-sharpness in general (resolution) – varies across the retina because of the uneven distribution and numbers of rods and cones. Regions with mainly rod cells were less sharp. Most color-sharpness cones were near the center, per A Miklosi. In the special high sharpness region about 20 percent were cone-cells as compared to three percent cones (two colors) overall for dogs, and about five percent for humans (three colors). Potential damages include detached or torn retinas, and damage by exposure to extremely bright light such as lasers. Repairs of detached and torn retinas were routine for humans. Damage with physical destruction of the light detection cells and related nerves wasn’t repairable.
Retina rod cells and “starlight-moonlight”: According to some speculation retina rod cells came into existence from cone cells. The reference said that rod cells have an outer layer that confines and directs light along the axis of each rod cell, maximizing effectiveness and making rods less reliant than cone cells on (and less able to use) reflected light from the tapetum in dim light. Cone cells would benefit much more from the reflected light of the tapetum than rods, at a slight loss perhaps in sharpness of their parts of the images which are formed from signals of both rods and cones in each tiny "pixel-like" part of the eye. The cones send the signals about the colors of the light which area-wise is detected mostly by the rods of the retina. [We presumed that in the periphery of the retina, there are two or three cones among each group of 100 rod-cells.]
If a dog (or human) had only retina rod cells, they might be sun-blinded in daylight unless wearing dark sun-blocking glasses. That suggested that normal dogs probably have nerve systems that reduce the output strength from their rod cells to be like the level from their cone cells in bright light. Conversely, when light levels are too low for the cone cells to provide useful signals, the rod cells signals operate at maximum strength (as for example under starlight, and moonlight.) Under conditions reported in 1989, dogs did distinguish colors in the region very near a 20 nm band of colors centered at 480 nm (cyan). An ability to sharply see colors near 480 nm was possibly unique to dogs and unlikely for humans with ordinary color vision.
Distribution of rods across the retina is not uniform, with mostly rods in the outer areas of the retina that do most of the peripheral (side) vision. Cones are mostly in the retina areas where the images fall of what a dog is looking directly at. Variation of the rod and cone distributions from one dog breed to another haven’t been documented (that we could find).
Suppression of signals from rod cells when cones were effectively working might account for difficulties in “dappled” light under shade trees, with well lit areas going colorless white, and the darker areas possessing colors. IF a wind was blowing, a dog might see colors flicker on and off for each patch of the ground, which might be confusing in searching for a particular color and shape object. A normal Border Collie encountered difficulty each year finding a yellow ball among yellow nearly round autumn tree leaves.
Except in their special high-sharpness zone, measurements by the year 2010 of dogs vision indicated that some breeds of dogs can see with the same sharpness at 65 feet as ordinary humans can (without glasses) at 20 feet. Apparently that was caused by the outer areas of the retinas consisting mostly of rods, and further as many or four or five rods were connected to each nerve going to the brain (which is great for seeing movement of images, but reduced sharpness by lumping together bits of the image.)
Night Vision - Ordinary dogs see usefully in dimmer light than humans - night vision- for two reasons:
1) they have more very light sensitive rods (which enable night vision)
2) they have an eye structure called the Tapetum Lucidum.
The tapetum is a reflective layer mainly useful to enhance color-vision, behind the retina (area of the light sensitive cells) that reflects light back through the retina (it gives the eerie shine at night). Dogs born, usually with blue eyes, without a tapetum for enhanced night vision are probably a little better able to see more sharply than ordinary dogs. Although some scientists to the year 2010 implied that the light reflected from the tapetum reduces the vision sharpness; that was likely mostly or exclusively for the color-cones, roughly doubling the amount of light available for color-vision in all lighting conditions. The physics of the "sheathing of rods structures mostly prevents the rods from accepting light at big angles to the axis of the rods; thus minimal loss of sharpness caused by wide angle scattering from the tapetum.
Best Resolution Special Zones –used to thread needles, read newspapers and legal papers. Cameras rarely, if ever, have dedicated high sharpness zones. The shape and quality of that zone varies from breed to breed- for understandable reasons.
Vision streak or “dot” (fovea) aspects: Measurements indicated that in the special high sharpness zone there are as many as 30,000 cone cells per square millimeter. When humans and short muzzle dogs wish to closely examine an object, regardless of the distance, they place the image of the object on the part of their retina where there is the greatest density of close-spaced vision cells. The special area for human eyes was called the “fovea” and for short muzzle dogs, is usually also called the visual streak although it is a “dot” like a human’s fovea. Human welders of metals, before effective dark glasses were required, often “burned-out” their fovea and consequently were unable to read newspapers and fine print, etc. A similar thing happened to people who stared at the sun too long during solar eclipses or while on drugs.
Each ordinary dog has their breeds’ type of visual streak. A notable dog-unique feature of the long muzzle type of visual streak is a wider high resolution portion at the end where the images from the extreme part of the side-peripheral vision falls. Such streaks are a definite proability, as demonstrated by a deaf dog that places in its peripheral vision an object it wants to see precisely.
Researchers reported that most breeds of dogs have a linear fovea (linear streak) of high resolution sight, as compared to the circular fovea spot of humans. Dogs with very short muzzles tend to have a nearly circular fovea.
Reflective layer for night vision: not present in some dogs, and never present in normal humans or our cameras. Absence correlates to blue eyes. Tapetum absence is often linked to deafness (night vision and acuity): So far as speculation permits, it was not obvious that the presence or absence of a dog’s tapetum would be ordinarily noticeable for dogs living as companion or service dogs who work mainly in daylight and who have little or no need for very sharp vision. Herding and other mostly outdoors working dogs such as Huskies might however depending on circumstance more need a tapetum or the sharper vision of blue eyes.
Most dogs and many other animals, excepting primates (humans) usually have a reflective layer behind their retinas, to nearly double the amount of light falling on the light detection cells. (If that could be done with solar cells to convert sunlight to electricity, they might extract nearly 24 percent of the available energy from sunlight, instead of about 12.)
S.Coren indicated that blue eye dogs usually lack the tapetum, and thus have less sensitivity for low light (night) vision, but because the light reflected interferes with the inbound light a tapetum reduces visual sharpness. A quantitative estimate of the actual amount of loss in vision sharpness would depend on the coherence of the reflected light, its wavelength and the thickness of the retina active zone, and “channeling” as is used in electronic “star-light” vision equipment of military forces.
Biological linkage of blue eyes, lacking a tapetum, to inherited dog deafness lead to some speculations that sharper vision blue eyes became genetically selected for in evolution, as partial compensation for genetic deafness inconveniences to dogs. A related aspect is the observation that puppies are born with blue eyes and develop brown (amber) eye colors by eight weeks of age, which implied that the emergence of the tapetum was later than the emergence of otherwise fully functional dog vision.
Color-vision – compared to humans: A simple sketch of a dog’s eye is in Figure 1. An ordinary dog’s eyes have the same major parts as human eyes, excepting that ordinary dogs have:
1) a reflective layer behind their retina, to enhance seeing in dim light, and
2) biological nerve connections for superior detection of movements in the images.
The quantities and arrangements of special cells, called rods and cones are different in dog’s eyes compared to humans. Most dogs have a different shape of the extra-sharp region in their eye than do humans. The length of each breed’s muzzle limits some of the ways that each breed uses their eyes. The angle between their “forehead” and their muzzle has an impact on their use of vision and some other actions. Except for moving objects, most dogs see a slightly less detailed world in general compared to humans. Long muzzle dogs can see wider to their left and right sides without turning their head than humans, but short muzzle dogs see to the sides nearly like humans. Three dimensional depth perception vision angle-width is slightly narrower than typical humans for long muzzle dogs, but comparable to humans for short muzzle dogs. Dogs excel at night vision. Dogs see colors differently than humans. Customarily all forms of color vision that differ from ordinary human are called “color blind.” Figure 2 had a human’s rough comparison of colors dogs see and what humans can see when viewing a “rainbow” color band (electro-magnetic spectrum). It should be kept in mind that some humans (like me) and dogs inherit a non-standard version of their species kind of color perception, vision sharpness, and night vision sensitivity; still not officially “blindness” or "legally blind."
Absence of one or more types of “cones” (color-vision): Research indicated that most dogs possess only two types of color-detection high resolution cone cells, in contrast to human typical possession of three color-types of cone cells. Because color information is obtained by comparing the strength of intensity signals from adjacent types of cones, colors are seen (mentally) for all areas of the spectrum where the sensitivities of two kinds of cones overlap. For a wavelength where only one kind of cone has sensitivity, the color is either seen as a shade of grey, or instead continues with some nominal color – essentially as for example colors at wavelengths longer than deep red are known as “infra-red,” and light wavelengths shorter than violet (seen by some insects and birds) are called “ultraviolet.”
An illustrative estimate of the colors seen by ordinary dogs and humans in daylight is in Figure 2. The black zones at the extremes indicate a lack of sensitivity to those colors. The situation in the 20 nm band at 480 nm is poorly known (to humans), and is shown as “white” because of overload of the rods. Or the same colors would be seen by humans there, but dim.
[1] Huskies: Health issues in the breed are mainly genetic such as seizures and defects of the eye (juvenile cataracts, corneal dystrophy, and progressive retinal atrophy). Aussies: Research shows that livestock are quicker to retreat from the predatory threat of a dark colored dog with light eyes than to dogs with brown irises that don't stand out compared to the coat as much.
[2] The ancient Greeks memorialized omnivorous (such as grapes hunting) adventures of Foxes in Aesop’s Fables.
[3] The feline slit vertical pupil serves the same general function as a dog’s horizontal high sharpness vision of the visual streak. Physics ensures that a narrow long electromagnetic-light aperture, as used by cats in bright light and some radar antennas, provides maximum sharpness perpendicular to the maximum length of the pupil area.
An ordinary dog’s eye has the same major parts as human eyes, excepting that most dogs also have: 1) a reflective layer called a tapetum behind their retina, to enhance seeing in dim light and 2) biology nerve connections for superior detection of movements in the images.
Genetics, diseases, accidents and old-age can damage the components of dogs’ eyes and nervous systems. Dr S. Coren [3] reported that old age pains and disabilities can make some dogs (and probably persons) bad tempered, unable to move quickly when in danger, and difficult to live with for other dogs, cats and humans. Deafness and blindness were almost never the direct causes of those unsocial behaviors.
Origins: As of 2010 it seemed that the differences of canine vision and human vision were “accidental” genetic adaptations to very different original environments and life-styles, before the proto-canines emerged in North America and proto-humans ancestors emerged in Africa - well over 15,000 years ago. Ref. A. Miklosi [2] and others[1, etc]: Probably dogs co-evolved with “modern” humans after humans began farming, following the ice age about 12,000 years before the present. Biological data from many species suggested that Always, a few of the dogs and humans in every generation, from the beginning, were born deaf, blind or deaf and blind. Many of those dogs were probably almost entirely white, or spotted, or owned “flashy” coats.
Introduction
Gotta be able to find the toilet door, and let the folks know when to open it. Smells can still be “read” by blind dogs and the places recalled, for getting around without rudely bumping into other dogs, people and the furniture. Can’t “read” the newspapers so well any more, or not at all. Never could spot the apricot colored toys on the brown rug, so that wasn’t a loss. IF the ears still work, the dog can learn to pretend it’s a bat or dolphin, or a Navy SONAR set and “see” things and distances by “reading” the echoes of sharp barks or noise vibrations. And if the usual inner ears quit working, or never did work right, dogs are born with about eight or nine other natural body biological ways to detect vibration-sounds for analysis by their brains, to communicate and navigate. A slightly desperate, possible socially risky way for newly blind of finding where things such as other dogs are, is to gently bump into them - - as all puppies do when they are about four weeks old and have no idea about socially proper behavior with adult dogs (who hate to be rudely bumped against or jumped upon.) Of course, at first when a blind (of deaf) dog bumps into its personal human, the dog likely will stay cuddled safely as close as possible “forever” or until the human takes a bath or goes out shopping (this sort of doggish action is often called “velcroing” because the dog sticks to the person like Velcro.)
A separate but connected set of dog-social challenges must be settled acceptably by each blind dog, even if the solutions amaze and puzzle the humans. Human supervision and counseling is important, just as though a dozen kindergarten kids were suddenly placed together in a play-ground to have fun without maiming each other. New ways of socializing with other dogs must be learned because a blind dog can’t see another dog’s “I’m friendly” body signals, and a deaf dog can’t hear another dog’s vocal invitation to play, or stay away.
Most adult dogs consider staring at them is rude because that might signal an adult dog that stares (except Border Collies) is deciding whether to grab the other dog. Various reports indicate that some blind dogs take advantage of being immune to the staring-games of others, such as Border Collies. But at dog parks a few anxious ordinary dogs reportedly give up waiting for the blind dog to attack and so launch a pre-emptive strike – which badly surprises the blind dog.
A likewise socially unexpected event to a stranger adult dog is meeting a blind dog who deliberately (like a poorly educated delinquent puppy-juvenile) bumps into the stranger. Some adult dogs (especially females who raised many puppies) are inclined to abruptly set about teaching a bumping dog to behave properly, without crashing carelessly into other adult dogs or people. However, some blind dogs when playing are remarkably casual and uncaring about bumping into furniture, etc as long as no blood gets shed.
Indoors and outdoors social walk-abouts are desirable while on a short leash, or even carried with their humans, so that the dogs can discover where everything is, and where they are. Scents used as labels by the humans are a sure help for that.
A large part of the social challenges for a blind, deaf, blind-deaf dog, ordinary dogs and any cats it associates with and their humans was called by Alexandra Semyonova (see reference) “linguistic consensus” and non-aggression dog-rules - namely agreeing on a set of signals that mean each of them is friendly and expects the other (regardless of how odd it seems) to be polite and never intentionally cause serious pain or wounds. Basically, everyone on the playground gets to have their turn in the fun, and nobody gets hurt on purpose. Many observations confirmed that if they can agree that they are each polite, if there is a mistake the antics will abruptly cease and probably the delinquent will appear to be repentant, regretting an error – despite whatever it was maybe being uncertain to the offender. Delinquents get ostracized-ignored and nobody plays with them, or even more remarkable occasionally the rest of the puppies form a “mob” like soccer players and thrash the delinquent.
I. Behaviors of some Blind Dogs
Blindness behaviors can be puzzling to people only used to ordinary dogs. Observations by a reliable observer were followed by comments. The observations of Shep were a welcome test to see if the research pieces ‘fit together’, without lots of behaviors left to be figured out later.
----- Original Message - Observations -----
My Shep has LOUSY eye sight, very skew-wiff (drooping), I have a pic of his eyes, the vet tells me the muscles in the eye to hold his eyes in normal position, the lower muscle is too tight & the top of the eye muscles are too loose, so his eyes are not correctly positioned, but other than that, Shep does not see well. He also has badly misshapen pupils -- all from the MERLE gene, father a red merle, mother a blue merle koolis X blue cattle dog & deafness from the merle & cattle dog genes, BUT a stunning merle coat.
I noticed that some colours BLEND with him e.g. we have a rubber Frisbee (disc) of a dull deep orange/apricot colour & when inside he cannot see this against our brown wooden floors, yet he can see it against green grass or DIRT.
Also, Shep cannot do jumps in (competition) agility because he does not see the jump bar --- white with blue tape in stripes along the bar - he cannot see this against grass. BUT he can see it with a background of white cement -- we played with this at home and he jumps like a beauty.
We use LARGER toys to play with Shep, as he cannot follow a tennis ball when thrown a distance or fast, BUT he can see it, if lobbed slowly close to him in the air and then he is a bullet going up to pluck it out of the air. I feel he has lousy distance vision and just okay close vision.
Shep can see 'glo' in the dark toys to play games, we have found he does not see well in bright sunshine, but sees much better at dusk & dawn & overcast skies, (and best in moonlight), BUT he cannot see - goes blind virtually - in dappled light under trees e.g. light filtered by leaves, but not fully shade & not full sunlight.
I would not say dogs cannot see colours, but I do not think humans actually KNOW how dogs see fully, or by what level of colour. I think dogs rely on movement and see that amazingly well.
&&& &&&
Comments from recent research and analysis were used to offer estimates based on Shep's described behavior and on published research on dogs and humans. I suspect that Shep's behavior demonstrated that he had several understandable oddities of his vision - compared to most other ordinary dogs and most humans.
My first reaction from Shep's sensitivity to sunlight is to suggest that Shep's eye "rod" sensor cells of his retina are incredibly more sensitive than his "cone" retina cells, and maybe more sensitive than those of ordinary dogs. Cone cells in humans eyes are the main color detectors and human rod cells were believed to Not be useful for color detection. Dogs tested in 1989 were using their rod-cells also as their brightness of grays detectors.
About the jump-bar, I first suggested that like certain humans Shep [me, sometimes] sees Bleen or Grue {a joke about people who can't see blue distinguishably from green. In the Welsh language, a single word designated all shades of color from green thru blue. Also, in humans who lived for a long time in the Mohave Desert of the US, for persons who almost never used sunglasses, the extreme ultraviolet (UV) light destroyed their ability to distinguish pale greens from pale blues.} Our computer simulations in fact suggest that Shep might entirely lack the ability to distinguish colors, because possibly (probably?) genetically he lacks useful cone cells, and must see entirely with his rod cells that only see shades of grey (see Figure 2, 3 and 4).
If his reflected light eye-color was reddish, he probably lacked the usual reflective layer in his eyes that helps dogs to see at night. Shep’s blue-green colored irises and pupils in daylight didn’t confirm or deny that he had a tapetum reflective layer. A rough guess from his ability to see a "Glo" ball at night is that he has a normal reflective layer just behind his retina.
Lousy distant vision is accountable because of odd shaped pupils; experiments on humans showed that their brains after a few days were able to see objects normally after they got used to wearing glasses that warped the "picture" as his distorted pupils do. Close in if he doesn't care about details, he would be able to see well enough, but way out at a distance he would fail to distinguish “small" fine features as well as ordinary dogs. A further problem for Shep would be that his odd pupils would make it impossible for him to effectively place vital far off small objects (such as those on the horizon) on his super-fine sharpness part of the retina, which is called the ‘visual streak.’
About his difficulty in "dappled" light - - my estimate was that Shep because of his pupils shapes was forced to rely mostly on his coarse rod detectors in the outer areas of his retinas, and unable to use his sharp-vision streak as ordinary long-muzzle dogs do. Which would also fit with being almost blinded by bright sunlight on his super-sensitive rod cells but seeing well in dim light (perhaps better than the other dogs?)
Geneticists estimated that such odd inherited vision and deafness traits came into existence before mammals did. But modern dog breeders by recent excessive inbreeding for fancy (marketable at high price!) flashy coats are concentrating the problem genes. Sadly, Dalmatians were a "poster child" dog breed that would cease to exist in their current form if the deafness/blindness/ blue-eyes genes were drastically reduced by zealous selective breeding against those traits.
[In response to the color chart] …That is amazing, it explains why Shep cannot see an orange-apricot Frisbee against brown flooring, it would BLEND on him. Yet he can see it against green grass and sky. Looking at the night vision, they have better light sensitivity for vision than us, how remarkable.
Bonding and educating their Startle Reflexes are the vital basis for helping blind dogs adapt to new homes, and learn to make full use of their biological natural abilities. Bonding is essentially the creation of complete mutual trust between the dog and its people. Providing regular good food, proper water available, plenty of safe secure exercise and mental exercise are necessary. Toilet training ought to be done with positive rewards and clear guidance to the dog about where and when things should be done. Advice of owners suggested that bonding and initial steps of education often needed about 30 days and some dogs suddenly responded after several months.
Usually a crate is very desirable to provide the dog a personal private place to be at night. They need to learn that when its new people leave the room and the house they will always come back again before the food and water run out, or something happens to the worried dog. Educating a blind or deaf dog’s startle reflex can be done by occasionally touching the dog gently, with treats in hand, and gentle words and petting, so that the dog concludes that new strange events are “good things” and good things are about to happen. A rescued dog may be anxious and insecure, with poor habits about the toilet and excessive guarding of food and toys, and maybe even its new people. The dog needs to learn that there is no reason for guarding food and other stuff that are reliable and not arbitrarily permanently taken away.
Scents mapping is a key method for blind dogs to keep track of where things are, find the door for the toilet, and generally get around without bumping into objects by accident. Most dogs even with ordinary sight and hearing make much use of observing the scents of nearby objects and places that they care about, and recall roughly where they are, so dogs born blind or who become blind can usually make prompt use of the scents to get around well. After getting discouraged by trying to figure out the chaotic aromas of the rescue places, of course a rescued dog must explore to learn the scents of a new home. We saw no proof that genetics or old age blindness or deafness cause losses of dogs’ ability to detect and make use of smells. However a loss or reduction of the ability to detect and analyze scents can happen to some dogs - - a person might want to verify that a dog’s nose is effective if their blind dog seemed unable to use smells.
Adapting for use of the natural ‘auxiliary’ biological additional "devices" of dogs that are means of detecting mechanical vibrations (sound): Succinctly, any dog that isn’t dead has many physical ways to detect the vibrations of sounds, analyze, and use the information. BAER tests only examine whether a dog can hear the same way as ordinary humans do. Certainly by 2004, scientists, as described by Dr S Coren, knew that dogs have many ways - - in addition to the exclusively inner-ear type of mechanical vibration detection (hearing) tested with the usual advertised BAER electronics wires in the head and ear-phones equipment. [See http://deafdogsforever.weebly.com, the adaptive hearing page.]
II. Biology and Physics of Dogs’ Eyes
Despite that they all have similar major eye parts; in details dogs’ eyes can differ from one breed to another, and differ in some key parts from ordinary humans eyes. Here the features of most common importance to blind dogs are discussed; with mention of only the most vital technical function and connections between key parts. Some breeds of dogs are near-sighted, i.e. unable to sharply focus their eyes for far away; other breeds exceeded many humans in distant vision (far-sighted or extra skilled vision.) A typical modern high quality digital camera has most of the same or equivalent parts and functions. Illustrative comparisons are made with cameras and human eyes.
Defects happen from injuries, diseases and from genetic causes. Certain genetic causes act mostly during the very earliest days of the formation of the embryos, although the consequences are usually noticed by humans perhaps after about nine days (varies with Breeds) of the dogs’ age when their eyes open, or even later when behavior oddities are noticed. Some of the genes that cause difficulties have been identified, and seem to often overlap in causing defects in the dog’s hearing (one-ear or two-ears deafness). Collateral impacts of the genes seem to include blue eyes, and flashy coats such as double dapples, white great Danes, and spotted white dogs.
Many instances of blindness were caused by glaucoma, diabetes, SARs or PRA. The genetic causes of the losses of nerve structures of SARs and PRA were reported in research reports to closely resemble the process of deterioration of deafness-nervous systems, and likewise in those situations involved melanin. SARs and PRA occurred mostly in older ages of the dogs impacted.
Old age for some dogs means ‘geriatric blindness’ including cataracts, often with increasing deafness, loss of cognitive functions and arthritis, etc. S Coren described various ways to minimize and delay the difficulties of old age.
Of course accidents such as car crashes, and exposures to chemicals can cause blindness and partial loss or difficulties of vision.
Lenses-cornea: Focusing for near or far sight, each eye's transparent lens is flexible so that muscles can contact or relax to focus the vision images sharply on the active cells of the retina Huskys’[1] Corneas are the protection against damage (comparable to the clear crystal over a watch face). Corneas are transparent front covers of the lenses. The corneas are kept moist and occasionally cleaned and covered by the eye-lids.
If a lens becomes off-color, hazy or cloudy-“milky” (translucent) the lens becomes warmer by absorbing light energy, which tends to stiffen it. Less light remains to reach the retina (so the light seems dimmer to the dog), and the light is typically scattered over many retina cells instead of sharply on the best cells for a sharp image (so the dog’s vision blurs, as a human would feel looking through dense fog) as a lens became more cloudy or milky. Old age is a common factor of cloudy lenses.
Different colors focus at different distances behind the lenses, so in theory retinas could be structured in color sensitive layers with the red sensitive layer closest to the lens, like old camera color film. Dogs’ retinas are more like a television or computer monitor screens with individual color detectors next to each other in roughly a single layer.
A common difficulty of lenses with age is their getting stiffer and failing to focus images over the entire range of distances needed. It seems unlikely that a dog would want to focus sharply on anything closer than the end of its nose; so the distance defining “near-sighted” is the length of the dog’s muzzle. Several breeds were studied in a project where the estimated minimum focus distance was about 15 inches (slightly far-sighted). A slightly far-sighted capability for sharp vision would shift the dog's detection apparatus possibly mainly to nose-odor smells at ranges where its nose is most effective for locating things, and deciding what can or should be done (such as eat it?) People rarely object or perhaps rarely notice their dog is near-sighted, or perhaps far-sighted. Eye-glasses “doggles” could correct such difficulties.
Iris, Pupil and Neurology Processes: The outer visible colored area around the usually black pupil is called the “iris.” Changes that shape the pupil are the vital feature in the inner edge of the iris. If the eye is spherical, generally the pupil ought to be round at all sizes of the openings in the iris. Probably an elliptical pupil is compatible with an almond shaped eye. For ordinary dogs, the pupil is widest under dim light and becomes very much smaller in bright light.
The area of the pupil controls the amount of distance from the eye that is in sharp focus. With tiny pupils (in bright light) the distance range of sharpness is maximum. In dim light, with the pupil wider open, the range of sharp focus becomes very short, and in those situations the health and adjustability of the eye’s lens becomes most important. Dim light outdoors of course is most likely to be encountered during sunrise, sunset-twilight, at night and under dense vegetation. It would be no surprise that ancestral feral canines tended to hunt big game in quite open terrain during daylight, and smaller game in near darkness and denser vegetation. Browsing[2] on fruit, grains and vegetation could be done relying mostly on scent-smells, at any time of day. An excellent sense of smell would reduce the need for excellent sensitivity to colors as experienced by humans, who typically (especially males) have limited odors detection abilities.
Control of the iris and pupil is probably done almost entirely with nerve-logic connections located with each eye, rather than relying entirely on back and forth signals traffic to processors in the brain. For example, the colors are seen by a comparison of signals from adjacent different types of cones. Detection by dogs of images movements are probably done with biological logic close behind the retina’s layer of rods and cones.
Oddities in the musculature operating an iris can cause the opening to be star-shaped, perhaps almost square, or vertical slits (in cats[3]), or sometimes simply “freeze” ceasing to change size. Consequences of odd shaped eye pupils seem to be mainly a drastic loss of sharpness-acuity, and especially a major loss of an ability to use their extremely high sharpness visual-streak (linear fovea). Misshapen pupils scatter the light rays of images over inappropriate (low resolution – poor sharpness) areas of its retina, which makes it difficult or impossible for such a dog to use its maximum sharpness visual streak in the way of ordinary dogs. So far as known to 2012, about all that can be done to relieve their difficulties is that a dog can try of its own initiative to discover that a special positioning of its head and eyes gets the best sharpness.
"Invisible bugs on the wall or flying in the sky" and other vision distractions that can become fatal: Incidentally, - about the possibility of dogs with bleeding in the eyes pawing at the eye (and some people report dogs staring at non-existent flying insects, or non-real insects on walls) - - such comparable behaviors can arise from what an ophthalmologist called "floaters" which are tiny bits of debris or tiny blood specks floating about in the fluid inside the eye-ball. They are most prominent against a light colored plain background, and might not be noticeable against a complex featured dark background such as is common outdoors.
Because the “flying” specks are inside the eyeball, the specks move with the dogs' eye movement and if the dog tries to catch one, the dog can die of whirling in circles instead of eating, etc. - as reported! The specks stay in one place if the dog stares, like a Border Collie tends to do, so that behavior is more typically reported among some breeds of deaf dogs. Usually ophthalmologist with human grade instruments can’t detect specific specks or debris floating about in the eye, so for humans the diagnosis is typically based on the victim's description, including age, conditions such as diabetes, alcoholism, certain chemical exposures, etc., including family history (genetics- same as dogs). How do I know about the behavior connections to that sort of eye-disorders? Easy - 30 years of personal experience!
Retina
In an old camera the film only functioned as an equivalent of the light detection cells of the retina (plus an image memory). Modern digital cameras have digital electronic light detectors and most of the functions equivalent to those of dogs’ eyes. In dogs’ eyes the retinas are where the images fall on the back inside surface of each eye, where the images are detected, partly analyzed locally, and then “coded” for quick transfer to the brain. The retina has a layer of light detector rods and cones, in front of a reflective layer that improves the use of dim light primarily by the color-vision cones, then a layer of biological logic neurons connecting between the light detectors and the ganglions and nerves that then transmit the encoded compressed signals to the brain for more analysis and action.
Scan rate - movement detection and “Movies”: Sensitivity of detecting movement experiments reported by S. Coren indicated that brain-processing of signals from their eyes permit some breeds of dogs to see moving objects as accurately as or better than most humans. However, unmoving objects are seen with coarser static biological logic. Most observed dogs were better able to detect movement than ordinary humans.
Accuracy-sharpness in general (resolution) – varies across the retina because of the uneven distribution and numbers of rods and cones. Regions with mainly rod cells were less sharp. Most color-sharpness cones were near the center, per A Miklosi. In the special high sharpness region about 20 percent were cone-cells as compared to three percent cones (two colors) overall for dogs, and about five percent for humans (three colors). Potential damages include detached or torn retinas, and damage by exposure to extremely bright light such as lasers. Repairs of detached and torn retinas were routine for humans. Damage with physical destruction of the light detection cells and related nerves wasn’t repairable.
Retina rod cells and “starlight-moonlight”: According to some speculation retina rod cells came into existence from cone cells. The reference said that rod cells have an outer layer that confines and directs light along the axis of each rod cell, maximizing effectiveness and making rods less reliant than cone cells on (and less able to use) reflected light from the tapetum in dim light. Cone cells would benefit much more from the reflected light of the tapetum than rods, at a slight loss perhaps in sharpness of their parts of the images which are formed from signals of both rods and cones in each tiny "pixel-like" part of the eye. The cones send the signals about the colors of the light which area-wise is detected mostly by the rods of the retina. [We presumed that in the periphery of the retina, there are two or three cones among each group of 100 rod-cells.]
If a dog (or human) had only retina rod cells, they might be sun-blinded in daylight unless wearing dark sun-blocking glasses. That suggested that normal dogs probably have nerve systems that reduce the output strength from their rod cells to be like the level from their cone cells in bright light. Conversely, when light levels are too low for the cone cells to provide useful signals, the rod cells signals operate at maximum strength (as for example under starlight, and moonlight.) Under conditions reported in 1989, dogs did distinguish colors in the region very near a 20 nm band of colors centered at 480 nm (cyan). An ability to sharply see colors near 480 nm was possibly unique to dogs and unlikely for humans with ordinary color vision.
Distribution of rods across the retina is not uniform, with mostly rods in the outer areas of the retina that do most of the peripheral (side) vision. Cones are mostly in the retina areas where the images fall of what a dog is looking directly at. Variation of the rod and cone distributions from one dog breed to another haven’t been documented (that we could find).
Suppression of signals from rod cells when cones were effectively working might account for difficulties in “dappled” light under shade trees, with well lit areas going colorless white, and the darker areas possessing colors. IF a wind was blowing, a dog might see colors flicker on and off for each patch of the ground, which might be confusing in searching for a particular color and shape object. A normal Border Collie encountered difficulty each year finding a yellow ball among yellow nearly round autumn tree leaves.
Except in their special high-sharpness zone, measurements by the year 2010 of dogs vision indicated that some breeds of dogs can see with the same sharpness at 65 feet as ordinary humans can (without glasses) at 20 feet. Apparently that was caused by the outer areas of the retinas consisting mostly of rods, and further as many or four or five rods were connected to each nerve going to the brain (which is great for seeing movement of images, but reduced sharpness by lumping together bits of the image.)
Night Vision - Ordinary dogs see usefully in dimmer light than humans - night vision- for two reasons:
1) they have more very light sensitive rods (which enable night vision)
2) they have an eye structure called the Tapetum Lucidum.
The tapetum is a reflective layer mainly useful to enhance color-vision, behind the retina (area of the light sensitive cells) that reflects light back through the retina (it gives the eerie shine at night). Dogs born, usually with blue eyes, without a tapetum for enhanced night vision are probably a little better able to see more sharply than ordinary dogs. Although some scientists to the year 2010 implied that the light reflected from the tapetum reduces the vision sharpness; that was likely mostly or exclusively for the color-cones, roughly doubling the amount of light available for color-vision in all lighting conditions. The physics of the "sheathing of rods structures mostly prevents the rods from accepting light at big angles to the axis of the rods; thus minimal loss of sharpness caused by wide angle scattering from the tapetum.
Best Resolution Special Zones –used to thread needles, read newspapers and legal papers. Cameras rarely, if ever, have dedicated high sharpness zones. The shape and quality of that zone varies from breed to breed- for understandable reasons.
Vision streak or “dot” (fovea) aspects: Measurements indicated that in the special high sharpness zone there are as many as 30,000 cone cells per square millimeter. When humans and short muzzle dogs wish to closely examine an object, regardless of the distance, they place the image of the object on the part of their retina where there is the greatest density of close-spaced vision cells. The special area for human eyes was called the “fovea” and for short muzzle dogs, is usually also called the visual streak although it is a “dot” like a human’s fovea. Human welders of metals, before effective dark glasses were required, often “burned-out” their fovea and consequently were unable to read newspapers and fine print, etc. A similar thing happened to people who stared at the sun too long during solar eclipses or while on drugs.
Each ordinary dog has their breeds’ type of visual streak. A notable dog-unique feature of the long muzzle type of visual streak is a wider high resolution portion at the end where the images from the extreme part of the side-peripheral vision falls. Such streaks are a definite proability, as demonstrated by a deaf dog that places in its peripheral vision an object it wants to see precisely.
Researchers reported that most breeds of dogs have a linear fovea (linear streak) of high resolution sight, as compared to the circular fovea spot of humans. Dogs with very short muzzles tend to have a nearly circular fovea.
Reflective layer for night vision: not present in some dogs, and never present in normal humans or our cameras. Absence correlates to blue eyes. Tapetum absence is often linked to deafness (night vision and acuity): So far as speculation permits, it was not obvious that the presence or absence of a dog’s tapetum would be ordinarily noticeable for dogs living as companion or service dogs who work mainly in daylight and who have little or no need for very sharp vision. Herding and other mostly outdoors working dogs such as Huskies might however depending on circumstance more need a tapetum or the sharper vision of blue eyes.
Most dogs and many other animals, excepting primates (humans) usually have a reflective layer behind their retinas, to nearly double the amount of light falling on the light detection cells. (If that could be done with solar cells to convert sunlight to electricity, they might extract nearly 24 percent of the available energy from sunlight, instead of about 12.)
S.Coren indicated that blue eye dogs usually lack the tapetum, and thus have less sensitivity for low light (night) vision, but because the light reflected interferes with the inbound light a tapetum reduces visual sharpness. A quantitative estimate of the actual amount of loss in vision sharpness would depend on the coherence of the reflected light, its wavelength and the thickness of the retina active zone, and “channeling” as is used in electronic “star-light” vision equipment of military forces.
Biological linkage of blue eyes, lacking a tapetum, to inherited dog deafness lead to some speculations that sharper vision blue eyes became genetically selected for in evolution, as partial compensation for genetic deafness inconveniences to dogs. A related aspect is the observation that puppies are born with blue eyes and develop brown (amber) eye colors by eight weeks of age, which implied that the emergence of the tapetum was later than the emergence of otherwise fully functional dog vision.
Color-vision – compared to humans: A simple sketch of a dog’s eye is in Figure 1. An ordinary dog’s eyes have the same major parts as human eyes, excepting that ordinary dogs have:
1) a reflective layer behind their retina, to enhance seeing in dim light, and
2) biological nerve connections for superior detection of movements in the images.
The quantities and arrangements of special cells, called rods and cones are different in dog’s eyes compared to humans. Most dogs have a different shape of the extra-sharp region in their eye than do humans. The length of each breed’s muzzle limits some of the ways that each breed uses their eyes. The angle between their “forehead” and their muzzle has an impact on their use of vision and some other actions. Except for moving objects, most dogs see a slightly less detailed world in general compared to humans. Long muzzle dogs can see wider to their left and right sides without turning their head than humans, but short muzzle dogs see to the sides nearly like humans. Three dimensional depth perception vision angle-width is slightly narrower than typical humans for long muzzle dogs, but comparable to humans for short muzzle dogs. Dogs excel at night vision. Dogs see colors differently than humans. Customarily all forms of color vision that differ from ordinary human are called “color blind.” Figure 2 had a human’s rough comparison of colors dogs see and what humans can see when viewing a “rainbow” color band (electro-magnetic spectrum). It should be kept in mind that some humans (like me) and dogs inherit a non-standard version of their species kind of color perception, vision sharpness, and night vision sensitivity; still not officially “blindness” or "legally blind."
Absence of one or more types of “cones” (color-vision): Research indicated that most dogs possess only two types of color-detection high resolution cone cells, in contrast to human typical possession of three color-types of cone cells. Because color information is obtained by comparing the strength of intensity signals from adjacent types of cones, colors are seen (mentally) for all areas of the spectrum where the sensitivities of two kinds of cones overlap. For a wavelength where only one kind of cone has sensitivity, the color is either seen as a shade of grey, or instead continues with some nominal color – essentially as for example colors at wavelengths longer than deep red are known as “infra-red,” and light wavelengths shorter than violet (seen by some insects and birds) are called “ultraviolet.”
An illustrative estimate of the colors seen by ordinary dogs and humans in daylight is in Figure 2. The black zones at the extremes indicate a lack of sensitivity to those colors. The situation in the 20 nm band at 480 nm is poorly known (to humans), and is shown as “white” because of overload of the rods. Or the same colors would be seen by humans there, but dim.
[1] Huskies: Health issues in the breed are mainly genetic such as seizures and defects of the eye (juvenile cataracts, corneal dystrophy, and progressive retinal atrophy). Aussies: Research shows that livestock are quicker to retreat from the predatory threat of a dark colored dog with light eyes than to dogs with brown irises that don't stand out compared to the coat as much.
[2] The ancient Greeks memorialized omnivorous (such as grapes hunting) adventures of Foxes in Aesop’s Fables.
[3] The feline slit vertical pupil serves the same general function as a dog’s horizontal high sharpness vision of the visual streak. Physics ensures that a narrow long electromagnetic-light aperture, as used by cats in bright light and some radar antennas, provides maximum sharpness perpendicular to the maximum length of the pupil area.
A normal dog tends to see dark red objects, etc. as roughly the same color as brown, easily seen against the sky or concrete, but not so easily against grass. A green ball might be very hard to see against grass or summer tree leaves, but easy to see against the blue sky or white clouds. Yellow and blue would be easily seen against grass, but a yellow object might be hard to find among autumn yellow-green leaves of shapes like the object's.
IF human theorists are correct, a dog that lacked one of its two types of cones would see only relative brightness, essentially running from black to white. So a dog seeing a white and blue striped stick on grass would see bright stripes and darker stripes where the darker stripes might be the same “grey” as the grass, like Figure 5. On light colored concrete or a white tent, the dog would likely mainly see dark grey where there were dark blue stripes. Light blue might be “invisible” on ordinary concrete. Figure 5. Illustrated Vision with Partial Blindness
Except for the region near 480 nm [iii], humans (such as me) born with only two types of cones are thought to see colors almost like the way typical dogs see colors. However if humans have three types of cones, those who have the red and nearly blue types of cones would theoretically see colors roughly like ordinary people, whereas if the two types of cones are toward the green-blue colors, again all of the colors could be seen although reds would be abnormally dim.
NOTE: In contrast to popular Internet color blindness jargon; there are three types of “dueteranopes” rather than just one. Dogs see sort of like a deuteranope human, with red-green color blindness (in 4% of male humans), with two cone types rather than three. [iii; J. Neitz, T. Giest, G.Jacobs; Dept of Psychology, University of California, Santa Barbara; Visual Neurosciences, (1989), 3, 119-125; Cambridge University Press)]
Genetic flaw possibilities include the absence of one of the color sensitive cone types or unusual arrangements of the cones and rods. Damage to the blue-green cones such as permanent bleaching happened from prolonged exposure to high levels of ultraviolet light, such as exist in the US Mojave Desert. So far as known to me in 2010, only an expensive fitting for color compensation glasses (doggles) could technically be provided. Most likely the outcome for most was learning to live with the difficulties.
A new 3D vision organ that senses blue-light, 480 nm), as base parts of eye retinas and other parts of bodies was described in May, 2011: [i.e. journal Scientific American (SC), May 2011, page 59 “Feeling Light, Not Seeing”. (Also search GOOGLE (pRGCS) )] The "new" organs which are a kind of nerve-ganglion used a light sensitive dye called 'melanopsin’. Researchers attributed functions including influence on eye-pupil reactions, setting the circadian rhythm (coupled rod and cone nerves with but able to act separately, as well as possibly reducing the depth of depression associated with low light levels. Commercial fluorescent lamps can emit light in the sensitive light frequency noted.
Infrared (IR): No research data suggests that dogs can with the rods and cones in the retina of their eyes detect light that humans label “infrared”, meaning more-red than can be seen as light by ordinary humans. Infrared light at higher brightness intensity as heat enhances chemical activity of the ordinary retina cells, leading to improved light sensitivity in the day time. S. Coren reported research that showed (as we observed about 2000) that puppies at birth possess an infrared detection capability that they can use to locate and seek their mother’s nipples. If adult dogs have a residual ability of that sort, it might be unnoticeable when added to their other sensoria, although dogs undoubtedly detect infrared light as heat when the light hits exposed, especially if hairless, parts of their body such as their noses.
Ultraviolet (UV): Insects and some vertebrate species such as reindeer can detect light invisible to ordinary humans, beyond violet. There are no known data indicating any dogs (or humans) have such UV visual detection ability. Dogs perhaps detect UV mainly by experiencing sunburns on exposed parts of their skin, especially where the skin is pinkish colored.
The Vision “Digital Camera” – eyes, skulls and consequences
Eyeball pointing (3-D, cross-eyes, and off-normal: Stereo (three-dimensional [3-D] vision perception is a learned ability ordinary puppy’s get after about three weeks of age. Studies suggest that the visual feeling of comparative depth (distance to a point of interest) is computed in the brain by comparing the amount of muscle contraction or extension required for each eye to precisely “overlap” the images of interest. Other learned processes of estimating distance, for humans as many as eight proven for astronauts, can be used by dogs to adapt for the absence of the ordinary 3D eye-muscles processes.
Experiments done on humans with “warped” eyeglasses indicated that after a few hours to days adults can (will usually) learn to mentally adapt to the peculiar orientation of the images falling on their retinas. Thus as of 2010, odd pointing-oriented eyeballs were believed to have little impact on a dog’s vision ability, except to puzzle their people.
Muzzle sizes, shapes and the (forehead) "Stop-angle": Modern dog breeds have varied muzzle shapes and forehead angles. Over-generalizing, the sight courser aerodynamically streamlined elegant hounds seem to tend toward long muzzles that taper back to their full width of skull, with a low sloping forehead; (perhaps in shape almost Neanderthalish), like wolves, and according to S Coren generally rated as relatively less trainable. The active herding dogs such as Border Collies tend to have moderately shorter muzzles that “flare out” at their base to a wide skull, and often possess a nearly square nearly 80 degrees forehead (perhaps reminding a person of a human wearing a mask of only a dog’s muzzle), and according to S. Coren the highest reputation for problems solving versatility and trainability. And of course, there are the Pugs, etc, who have very short muzzles, with eye placements and most eye features very like humans.
Because dogs generally tend to hold their forehead ‘stop-angle’ surface perpendicular to the ground for vision at a moderate distance, perhaps 50 feet, the consequence of a backward tilted stop angle is that the slashing and gripping teeth are closer to the ground while running, of the long muzzle low slope angle forehead dogs. That from an engineering perspective made sense for ancestral dogs (and ur-wolves) that caught their prey while running at max speeds. Conversely, shorter muzzle dogs self-selectively bred to eat from human debris can see what they are about to eat far better. Some puppies are borne with low forehead slope because of birth canal induced deformations, (as can happen to humans also) but all those that were seen by us recovered normal skull profiles as their skulls expanded when their eyes opened fully for the first time by the age of about nine (9) days.
The implication, from observation of dogs who had skewed pointing of their eyes because of genetics, was that in general their brains after their birth or from the time of an accident, etc. automatically self-adapted to seeing reality correctly, as it actually existed, despite oddities of musculature. Cross-eyes, for example, could cause some loss of peripheral vision, and a smaller angular three-dimensional field of view. Likewise other oddities probably cause only minor inconveniences to the dog, unless unattractive (a social stigma) to their potential humans.
Skull width, eye-spacing and eye-ball orientation: Authorities such as A. Miklosi reported that typical domestic dogs (breed unspecified!) had comparatively wider skulls for their skull length than expected if dogs were wolves (which they aren’t). The relatively wider skulls provided more effective three dimensional vision to greater distances forward of the dogs’ skulls and shorter muzzles obstructed less of the dog’s forward field and downward view. Breeding of dogs for very short muzzles created vision fields comparable to humans, with unknown benefits other than titillating maternal instincts of some humans.
Image storage short and long term: Some digital cameras can display each new picture for a few seconds, while at the same time sending the data to memory chips for nearly permanent long term storage, where it again later could be viewed, edited, and perhaps erased (forgotten.)
Dogs with ordinary brains can process images similarly. Physical damage by accidents, diseases, chemicals and old age can each reduce a dog’s short term and long term memory of images. S. Coren and others offered advice by 2004 about enhancing an old dog’s resistance to losses. The advice applied partly to losses of brain function caused by other causes, in addition to old age.
Three dimensional (3D) and two dimensional (2D) Ordinary Fields of View: While looking straight ahead, long muzzle dogs who have their eyes somewhat on the sides of their muzzles-skulls see partially behind themselves at a distance (where it’s not blocked by their bodies.) Dogs with muzzles as short as those of humans only see to the sides about the same as humans. While seeing upward when looking directly forward, most dogs regardless of muzzle length can see upward about as well as a human of the dog’s height. Certain vision losses can cause vision narrowing into almost a “tunnel” in the front of the dog's field of view.
Three dimensional vision requires use of both eyes. So 3D vision is available only in front where the vision of the eyes overlap, and is not blocked by the muzzle. Farther out than a fairly short distance in front (perhaps 25 feet), the images seen by each eye become so nearly identical that at greater distances they can’t see in 3D; everything further is seen as 2D and a dog must estimate distances by one or more of maybe 12 other methods. On the sides where only one eye sees, the scene is 2-D.
Loss of sensitivity of the eye muscles and nerves, because of fatigue, disease (a stroke, etc) or old age are known to cause a loss of 3D vision ability, and can cause their brains to receive an overlapping set of images. When a dog or person has good general health, there is a good chance of gradual recovery by adaptive self-activated brain “synestesia” and the growth of new nerve-neurons, under supervision. We observed details of vision loss of a dog by stroke and in a human by fatigue.
Typical fields of view of a human and a dog, Figure 6: Due to the “short muzzle” placement of their eyes, humans have a 3D overlap of the sight of the eyes of roughly 140 degrees horizontally, and almost the same vertically. For dogs, depending on the breed and muzzle length it is directly ahead about 100 degrees across and perhaps 50 degrees upward – modified by the dog’s movement of its head and neck, and below its muzzle-none.
With the 2-D areas added, a human’s span of vision might be nearly 180 degrees. For short muzzle dogs, it’s about the same as humans. Long muzzle dogs typically have a wider 2-D field to the sides and somewhat behind of nearly 250 degrees, except where blocked by their body, allowing them to see more. Sharpness of images for humans is usually much less in the 2-D zones, but where dogs can apply their linear vision streaks the dogs may have images at least as sharp as those of humans.
Adapted integrated use of all available dog-sense abilities: Recent research on humans and other animal species confirmed that all have a considerable ability for long term adjustment of their brains by integrated adaptive use of whatever forms were available to each animal of vision, of many ways of mechanical vibration detection (hearing), and of detecting smells
NOTE: In contrast to popular Internet color blindness jargon; there are three types of “dueteranopes” rather than just one. Dogs see sort of like a deuteranope human, with red-green color blindness (in 4% of male humans), with two cone types rather than three. [iii; J. Neitz, T. Giest, G.Jacobs; Dept of Psychology, University of California, Santa Barbara; Visual Neurosciences, (1989), 3, 119-125; Cambridge University Press)]
Genetic flaw possibilities include the absence of one of the color sensitive cone types or unusual arrangements of the cones and rods. Damage to the blue-green cones such as permanent bleaching happened from prolonged exposure to high levels of ultraviolet light, such as exist in the US Mojave Desert. So far as known to me in 2010, only an expensive fitting for color compensation glasses (doggles) could technically be provided. Most likely the outcome for most was learning to live with the difficulties.
A new 3D vision organ that senses blue-light, 480 nm), as base parts of eye retinas and other parts of bodies was described in May, 2011: [i.e. journal Scientific American (SC), May 2011, page 59 “Feeling Light, Not Seeing”. (Also search GOOGLE (pRGCS) )] The "new" organs which are a kind of nerve-ganglion used a light sensitive dye called 'melanopsin’. Researchers attributed functions including influence on eye-pupil reactions, setting the circadian rhythm (coupled rod and cone nerves with but able to act separately, as well as possibly reducing the depth of depression associated with low light levels. Commercial fluorescent lamps can emit light in the sensitive light frequency noted.
Infrared (IR): No research data suggests that dogs can with the rods and cones in the retina of their eyes detect light that humans label “infrared”, meaning more-red than can be seen as light by ordinary humans. Infrared light at higher brightness intensity as heat enhances chemical activity of the ordinary retina cells, leading to improved light sensitivity in the day time. S. Coren reported research that showed (as we observed about 2000) that puppies at birth possess an infrared detection capability that they can use to locate and seek their mother’s nipples. If adult dogs have a residual ability of that sort, it might be unnoticeable when added to their other sensoria, although dogs undoubtedly detect infrared light as heat when the light hits exposed, especially if hairless, parts of their body such as their noses.
Ultraviolet (UV): Insects and some vertebrate species such as reindeer can detect light invisible to ordinary humans, beyond violet. There are no known data indicating any dogs (or humans) have such UV visual detection ability. Dogs perhaps detect UV mainly by experiencing sunburns on exposed parts of their skin, especially where the skin is pinkish colored.
The Vision “Digital Camera” – eyes, skulls and consequences
Eyeball pointing (3-D, cross-eyes, and off-normal: Stereo (three-dimensional [3-D] vision perception is a learned ability ordinary puppy’s get after about three weeks of age. Studies suggest that the visual feeling of comparative depth (distance to a point of interest) is computed in the brain by comparing the amount of muscle contraction or extension required for each eye to precisely “overlap” the images of interest. Other learned processes of estimating distance, for humans as many as eight proven for astronauts, can be used by dogs to adapt for the absence of the ordinary 3D eye-muscles processes.
Experiments done on humans with “warped” eyeglasses indicated that after a few hours to days adults can (will usually) learn to mentally adapt to the peculiar orientation of the images falling on their retinas. Thus as of 2010, odd pointing-oriented eyeballs were believed to have little impact on a dog’s vision ability, except to puzzle their people.
Muzzle sizes, shapes and the (forehead) "Stop-angle": Modern dog breeds have varied muzzle shapes and forehead angles. Over-generalizing, the sight courser aerodynamically streamlined elegant hounds seem to tend toward long muzzles that taper back to their full width of skull, with a low sloping forehead; (perhaps in shape almost Neanderthalish), like wolves, and according to S Coren generally rated as relatively less trainable. The active herding dogs such as Border Collies tend to have moderately shorter muzzles that “flare out” at their base to a wide skull, and often possess a nearly square nearly 80 degrees forehead (perhaps reminding a person of a human wearing a mask of only a dog’s muzzle), and according to S. Coren the highest reputation for problems solving versatility and trainability. And of course, there are the Pugs, etc, who have very short muzzles, with eye placements and most eye features very like humans.
Because dogs generally tend to hold their forehead ‘stop-angle’ surface perpendicular to the ground for vision at a moderate distance, perhaps 50 feet, the consequence of a backward tilted stop angle is that the slashing and gripping teeth are closer to the ground while running, of the long muzzle low slope angle forehead dogs. That from an engineering perspective made sense for ancestral dogs (and ur-wolves) that caught their prey while running at max speeds. Conversely, shorter muzzle dogs self-selectively bred to eat from human debris can see what they are about to eat far better. Some puppies are borne with low forehead slope because of birth canal induced deformations, (as can happen to humans also) but all those that were seen by us recovered normal skull profiles as their skulls expanded when their eyes opened fully for the first time by the age of about nine (9) days.
The implication, from observation of dogs who had skewed pointing of their eyes because of genetics, was that in general their brains after their birth or from the time of an accident, etc. automatically self-adapted to seeing reality correctly, as it actually existed, despite oddities of musculature. Cross-eyes, for example, could cause some loss of peripheral vision, and a smaller angular three-dimensional field of view. Likewise other oddities probably cause only minor inconveniences to the dog, unless unattractive (a social stigma) to their potential humans.
Skull width, eye-spacing and eye-ball orientation: Authorities such as A. Miklosi reported that typical domestic dogs (breed unspecified!) had comparatively wider skulls for their skull length than expected if dogs were wolves (which they aren’t). The relatively wider skulls provided more effective three dimensional vision to greater distances forward of the dogs’ skulls and shorter muzzles obstructed less of the dog’s forward field and downward view. Breeding of dogs for very short muzzles created vision fields comparable to humans, with unknown benefits other than titillating maternal instincts of some humans.
Image storage short and long term: Some digital cameras can display each new picture for a few seconds, while at the same time sending the data to memory chips for nearly permanent long term storage, where it again later could be viewed, edited, and perhaps erased (forgotten.)
Dogs with ordinary brains can process images similarly. Physical damage by accidents, diseases, chemicals and old age can each reduce a dog’s short term and long term memory of images. S. Coren and others offered advice by 2004 about enhancing an old dog’s resistance to losses. The advice applied partly to losses of brain function caused by other causes, in addition to old age.
Three dimensional (3D) and two dimensional (2D) Ordinary Fields of View: While looking straight ahead, long muzzle dogs who have their eyes somewhat on the sides of their muzzles-skulls see partially behind themselves at a distance (where it’s not blocked by their bodies.) Dogs with muzzles as short as those of humans only see to the sides about the same as humans. While seeing upward when looking directly forward, most dogs regardless of muzzle length can see upward about as well as a human of the dog’s height. Certain vision losses can cause vision narrowing into almost a “tunnel” in the front of the dog's field of view.
Three dimensional vision requires use of both eyes. So 3D vision is available only in front where the vision of the eyes overlap, and is not blocked by the muzzle. Farther out than a fairly short distance in front (perhaps 25 feet), the images seen by each eye become so nearly identical that at greater distances they can’t see in 3D; everything further is seen as 2D and a dog must estimate distances by one or more of maybe 12 other methods. On the sides where only one eye sees, the scene is 2-D.
Loss of sensitivity of the eye muscles and nerves, because of fatigue, disease (a stroke, etc) or old age are known to cause a loss of 3D vision ability, and can cause their brains to receive an overlapping set of images. When a dog or person has good general health, there is a good chance of gradual recovery by adaptive self-activated brain “synestesia” and the growth of new nerve-neurons, under supervision. We observed details of vision loss of a dog by stroke and in a human by fatigue.
Typical fields of view of a human and a dog, Figure 6: Due to the “short muzzle” placement of their eyes, humans have a 3D overlap of the sight of the eyes of roughly 140 degrees horizontally, and almost the same vertically. For dogs, depending on the breed and muzzle length it is directly ahead about 100 degrees across and perhaps 50 degrees upward – modified by the dog’s movement of its head and neck, and below its muzzle-none.
With the 2-D areas added, a human’s span of vision might be nearly 180 degrees. For short muzzle dogs, it’s about the same as humans. Long muzzle dogs typically have a wider 2-D field to the sides and somewhat behind of nearly 250 degrees, except where blocked by their body, allowing them to see more. Sharpness of images for humans is usually much less in the 2-D zones, but where dogs can apply their linear vision streaks the dogs may have images at least as sharp as those of humans.
Adapted integrated use of all available dog-sense abilities: Recent research on humans and other animal species confirmed that all have a considerable ability for long term adjustment of their brains by integrated adaptive use of whatever forms were available to each animal of vision, of many ways of mechanical vibration detection (hearing), and of detecting smells
III. Origins of Genetic Blindness (and deafness): Gradual or Sudden
Origins matter as an aid to estimate the causes of vision challenges of modern dogs, and thus perhaps ways that the occurrence can be reduced or treated. Recent advances in archeology and genetics provided major improvements, many that were startling conflicts with the “folk-wisdom” of earlier scientific experts, including at least one Nobel Prize winner. The main features were traced, and some references offered.
Boutique and companion dogs, working dogs –herding, tracking, coursing, fighting and other breeds were almost certainly long ago and far away Canis lupus variabilis and before that proto-wolves. The ur-wolves were omnivores, enjoying small game such as mice when they could get them and the weak of the big animal herds. Primordial genetic ur-wolves species probably divided into the proto-wolves who later co-evolved with dogs to become the modern wolves, and the pre-domestic Canis lupus variabilis predecessors known from archeology. The Canis lupus variabilis likely then became the ancestors of our modern domestic dogs after they met and co-adapted for cultural and physical co-evolution with the ancestors of modern humans.
By 2010, scientific research indicated that the canis lupus variabilis almost certainly came into existence under the extreme biological stresses of the great ice ages, while migrating from North America eventually all across Asia into Europe. Archeologies suggest that dogs domesticated themselves to live “symbiotically,” with unintended mutual benefits with humans quietly where and when at last humans became settled farmer-herders.
The origin stock that became modern dog breeds, based on good data, probably existed 12,000 years or more before the present. Except by a mental “time machine,” we can’t know exactly their ancient general behaviors, deafness and blindness, from the dog skeletons buried with humans (assumed to be domestic dogs) and Canis lupis lupis (ancient ancestor wolves) who co-evolved with domestic dogs and humans. Genetics data of modern wolves by the year 2010 seemed to indicate that modern wolves are descendants of the few ancient wolves that missed the gene mutations that formed modern domestic dogs – modern domestic dogs are NOT wolves and haven’t been genetically the same as wolves for over 12,000 years. Comparative observations of modern intrinsic behavior of domestic dogs can benefit by learning from comparisons to other branches of the ur-canis lupus, just as we can learn by comparing domestic dogs' biology and behaviors to cats and other species.
Having arrived in the discussion at 2010, to discuss genetically blind dogs (and deaf), we again consider the thousands of years before even the ur-wolves prowled North America. The DNA seems to confirm that genetic blindness and deafness emerged in ancient ‘primordial’ vertebrates, and continues in mammals. Breeding diversity ensured that the genes of blindness and deafness were rarely seen in living animals. The currently known evidence of their existence included the world-wide folk-wisdom of white and spotted mammals or reptiles or fish. Recurrence of those genetic rarities continued into modern times when sculptures, manuscripts and books described them. A modern branch of those genetic rarities can be met on our streets and in homes as Dalmatians.
The popular notion that Darwinian evolution would eliminate blindness and deafness genes of dogs, because blindness is profoundly counter-survival, ran afoul of the probable fact that the impacts of the particular genes vary enormously from creating “flashy coats”, to deafness, blindness, and probably various neurological difficulties including full or partial loss of scent detection ability. Flashy coats probably had group survival value in early years by letting some of the animals camouflage better in mixed open lands, forest margins, seasonal terrain colors shifts and most recently by attracting the competitive eye of rich human fashionistas.
With the flashy coasts came deafness that had probably been for millennia a trait of little difficulty in groups (see S Coren) but which humans treated among themselves as a social defect “stigma” sexually transmitted disease. More blindness at birth or soon after was an un-removable built-in consequence of modern “pure-bred” breeding that concentrated gene mutations into smaller and smaller groups, thus escalating the numbers of the deaf and blind in certain breeds. Recent temporary fads of breeding for flashy coats created many more white great Danes, double-dapple dachshunds and double merle dogs - a disaster for domestic dogs expected to live with humans, where most humans consider blindness or deafness of members of any species a major physical and social stigma-defect. That fashion-fad reportedly faded away by 2011, although some of those dogs were still alive in 2012 as reported in our surveys.
References
1. Alexandra Semyonova , "The 100 Silliest Things People Say About Dogs", 2009, Hastings Press, England, a serious book
2. Adam Miklosi, “Dog Behaviour, Evolution, and Cognition”, 2007, Oxford Biology
3. Stanley Coren, "How Dogs Think", 2004, Free Press; [In addition to over 90 percent excellent information, regrettably the author included many deaf-dogs superstitions almost without discussion of their misleading nature]
4. Virginia Broitman; “Bow Wow” 2010, clicker training DVDs, positive reinforcement to teach skills and tricks; <www.takeabowwow.com>Web sources.
5. Sean Senechal, “Dogs Can Sign, Too: A Breakthrough Method for Teaching Your Dog to Communicate,” 2009; Random House
6. Internet:
Wikipedia
<http:// www.neitzvision.com/images/cvdog.pdf>
< http://www.diycalculator.com/sp-cvision.shtml>
NOTES:
Humans trying to see a very dim object at night are advised to look a little to one side of the object, because if they look exactly at it the image will fall on their fovea of very sharp vision cone cells that are nearly useless in dim light, and instead if the image is moved to the side it will fall on their rod cells that are very much more sensitive to dim light (but don’t see colors.) Similarly, some dogs were observed to turn their head slightly away from the person of interest, so that the person’s face image fell on the extra wide section of their vision-streak where ordinarily they see the details near their extreme side angles on the “horizon” (where their ancestors might expect an escaping bit of food to be moving, a charming member of the other gender, or an adversary to appear..)
Dogs tilting their head at about a 45 degree sidewise angle when looking “questioningly” at a human were often indeed likely to be questioning what the human has on its mind, as portrayed by the human’s face expression, body posture and any micro-motions of its hands, feet or face muscles. The dog was placing as well as it can, the human’s key features of interest to the dog, on the dog’s optical vision-streak of maximum sharpness and colors sensitivity. A blind dog will of course attempt to do much the same thing using its hearing, tilting its head. A blind dog that is inner-ear-deaf can use one or more of its other methods of detecting mechanical vibrations (sound) through air, solid things such as walls or floors or water. [See ref. 3]
Synesthesia [Edited - for blind and deaf dogs] Source: Wikipedia, the encyclopedia Feb 2011
Synesthesia technically it is a neurologically-based condition in which detections-stimulation of a sensory or cognitive pathway leads to automatic, involuntary experiences in a second sensory or cognitive pathway. Humans who have such experiences are known as “synesthetes”. [Some are well paid “pilots” using HUD devices (Head Up Displays)! Others who use them probably are blind, deaf and blind-deaf dogs.]… It’s estimated that it could possibly be as prevalent as 1 in 23 persons over its variants. Synesthesia is sometimes reported by humans as a result of blindness or deafness. … sensory linkings such as "sound ->vision" or "touch -> hearing". Psychological research demonstrated that the experiences can have behavior consequences, while functional neuroimaging studies identified differences in patterns of brain activation. Psychologists and neuro-scientists study it for its inherent interest, and for the insights it may give into thinking and perceptual processes that occur in all. … most report their experiences are neutral, or even pleasant. Rather, like color blindness or perfect pitch, synesthesia is a difference in perceptual experience and the term just points at the brain basis of the difference. … For example, sound-color synesthetes, as a group, tend to see lighter colors for higher sounds[20]… individuals report differing triggers for their sensations, and differing intensities of experiences. ... There were common elements. ... Neurologist Richard Cytowic identifies the following diagnostic criteria:
- Synesthesia is involuntary and automatic.
- perceptions often have a sense of "location.”… "looking at" or "going to" a particular place to attend to the experience.
- consistent and generic
- memorable.
- laden with affect.
… Synesthetes often reported that they were unaware their experiences were unusual [unless new or] until they realized other people did not have them... Most report that their experiences are pleasant or neutral, although, in rare cases, they report that their experiences can lead to a some sensory overload (confusion.) ... Most report it as a gift—an additional "hidden" sense—something they would not want to miss. Most become aware in their childhood. Some apply this in daily life ... Synesthesia can occur between nearly any two senses [Sound->sight] or perceptual modes. ... Sound → color synesthesia … voice, music, and environment sounds such as clattering dishes or dog barks [or thunder storms?] trigger color and simple shapes that arise, move around, and then fade when the sound ends. Sound often changes the perceived hue, brightness, scintillation, and directional movement… People rarely agree on what color a given sound is. .…. groups say that loud tones are brighter than soft tones and that lower tones are darker than higher tones [i.e. can form textures in the reflections from complex material and surfaces]
=> An editor of this document experienced near-ultrasonic sound-vibration induced ‘location-synesthesia triggered by “lost” cries of three puppies, of a Border Collie puppies litter.
To return to the Page TOP click here:
Origins matter as an aid to estimate the causes of vision challenges of modern dogs, and thus perhaps ways that the occurrence can be reduced or treated. Recent advances in archeology and genetics provided major improvements, many that were startling conflicts with the “folk-wisdom” of earlier scientific experts, including at least one Nobel Prize winner. The main features were traced, and some references offered.
Boutique and companion dogs, working dogs –herding, tracking, coursing, fighting and other breeds were almost certainly long ago and far away Canis lupus variabilis and before that proto-wolves. The ur-wolves were omnivores, enjoying small game such as mice when they could get them and the weak of the big animal herds. Primordial genetic ur-wolves species probably divided into the proto-wolves who later co-evolved with dogs to become the modern wolves, and the pre-domestic Canis lupus variabilis predecessors known from archeology. The Canis lupus variabilis likely then became the ancestors of our modern domestic dogs after they met and co-adapted for cultural and physical co-evolution with the ancestors of modern humans.
By 2010, scientific research indicated that the canis lupus variabilis almost certainly came into existence under the extreme biological stresses of the great ice ages, while migrating from North America eventually all across Asia into Europe. Archeologies suggest that dogs domesticated themselves to live “symbiotically,” with unintended mutual benefits with humans quietly where and when at last humans became settled farmer-herders.
The origin stock that became modern dog breeds, based on good data, probably existed 12,000 years or more before the present. Except by a mental “time machine,” we can’t know exactly their ancient general behaviors, deafness and blindness, from the dog skeletons buried with humans (assumed to be domestic dogs) and Canis lupis lupis (ancient ancestor wolves) who co-evolved with domestic dogs and humans. Genetics data of modern wolves by the year 2010 seemed to indicate that modern wolves are descendants of the few ancient wolves that missed the gene mutations that formed modern domestic dogs – modern domestic dogs are NOT wolves and haven’t been genetically the same as wolves for over 12,000 years. Comparative observations of modern intrinsic behavior of domestic dogs can benefit by learning from comparisons to other branches of the ur-canis lupus, just as we can learn by comparing domestic dogs' biology and behaviors to cats and other species.
Having arrived in the discussion at 2010, to discuss genetically blind dogs (and deaf), we again consider the thousands of years before even the ur-wolves prowled North America. The DNA seems to confirm that genetic blindness and deafness emerged in ancient ‘primordial’ vertebrates, and continues in mammals. Breeding diversity ensured that the genes of blindness and deafness were rarely seen in living animals. The currently known evidence of their existence included the world-wide folk-wisdom of white and spotted mammals or reptiles or fish. Recurrence of those genetic rarities continued into modern times when sculptures, manuscripts and books described them. A modern branch of those genetic rarities can be met on our streets and in homes as Dalmatians.
The popular notion that Darwinian evolution would eliminate blindness and deafness genes of dogs, because blindness is profoundly counter-survival, ran afoul of the probable fact that the impacts of the particular genes vary enormously from creating “flashy coats”, to deafness, blindness, and probably various neurological difficulties including full or partial loss of scent detection ability. Flashy coats probably had group survival value in early years by letting some of the animals camouflage better in mixed open lands, forest margins, seasonal terrain colors shifts and most recently by attracting the competitive eye of rich human fashionistas.
With the flashy coasts came deafness that had probably been for millennia a trait of little difficulty in groups (see S Coren) but which humans treated among themselves as a social defect “stigma” sexually transmitted disease. More blindness at birth or soon after was an un-removable built-in consequence of modern “pure-bred” breeding that concentrated gene mutations into smaller and smaller groups, thus escalating the numbers of the deaf and blind in certain breeds. Recent temporary fads of breeding for flashy coats created many more white great Danes, double-dapple dachshunds and double merle dogs - a disaster for domestic dogs expected to live with humans, where most humans consider blindness or deafness of members of any species a major physical and social stigma-defect. That fashion-fad reportedly faded away by 2011, although some of those dogs were still alive in 2012 as reported in our surveys.
References
1. Alexandra Semyonova , "The 100 Silliest Things People Say About Dogs", 2009, Hastings Press, England, a serious book
2. Adam Miklosi, “Dog Behaviour, Evolution, and Cognition”, 2007, Oxford Biology
3. Stanley Coren, "How Dogs Think", 2004, Free Press; [In addition to over 90 percent excellent information, regrettably the author included many deaf-dogs superstitions almost without discussion of their misleading nature]
4. Virginia Broitman; “Bow Wow” 2010, clicker training DVDs, positive reinforcement to teach skills and tricks; <www.takeabowwow.com>Web sources.
5. Sean Senechal, “Dogs Can Sign, Too: A Breakthrough Method for Teaching Your Dog to Communicate,” 2009; Random House
6. Internet:
Wikipedia
<http:// www.neitzvision.com/images/cvdog.pdf>
< http://www.diycalculator.com/sp-cvision.shtml>
NOTES:
Humans trying to see a very dim object at night are advised to look a little to one side of the object, because if they look exactly at it the image will fall on their fovea of very sharp vision cone cells that are nearly useless in dim light, and instead if the image is moved to the side it will fall on their rod cells that are very much more sensitive to dim light (but don’t see colors.) Similarly, some dogs were observed to turn their head slightly away from the person of interest, so that the person’s face image fell on the extra wide section of their vision-streak where ordinarily they see the details near their extreme side angles on the “horizon” (where their ancestors might expect an escaping bit of food to be moving, a charming member of the other gender, or an adversary to appear..)
Dogs tilting their head at about a 45 degree sidewise angle when looking “questioningly” at a human were often indeed likely to be questioning what the human has on its mind, as portrayed by the human’s face expression, body posture and any micro-motions of its hands, feet or face muscles. The dog was placing as well as it can, the human’s key features of interest to the dog, on the dog’s optical vision-streak of maximum sharpness and colors sensitivity. A blind dog will of course attempt to do much the same thing using its hearing, tilting its head. A blind dog that is inner-ear-deaf can use one or more of its other methods of detecting mechanical vibrations (sound) through air, solid things such as walls or floors or water. [See ref. 3]
Synesthesia [Edited - for blind and deaf dogs] Source: Wikipedia, the encyclopedia Feb 2011
Synesthesia technically it is a neurologically-based condition in which detections-stimulation of a sensory or cognitive pathway leads to automatic, involuntary experiences in a second sensory or cognitive pathway. Humans who have such experiences are known as “synesthetes”. [Some are well paid “pilots” using HUD devices (Head Up Displays)! Others who use them probably are blind, deaf and blind-deaf dogs.]… It’s estimated that it could possibly be as prevalent as 1 in 23 persons over its variants. Synesthesia is sometimes reported by humans as a result of blindness or deafness. … sensory linkings such as "sound ->vision" or "touch -> hearing". Psychological research demonstrated that the experiences can have behavior consequences, while functional neuroimaging studies identified differences in patterns of brain activation. Psychologists and neuro-scientists study it for its inherent interest, and for the insights it may give into thinking and perceptual processes that occur in all. … most report their experiences are neutral, or even pleasant. Rather, like color blindness or perfect pitch, synesthesia is a difference in perceptual experience and the term just points at the brain basis of the difference. … For example, sound-color synesthetes, as a group, tend to see lighter colors for higher sounds[20]… individuals report differing triggers for their sensations, and differing intensities of experiences. ... There were common elements. ... Neurologist Richard Cytowic identifies the following diagnostic criteria:
- Synesthesia is involuntary and automatic.
- perceptions often have a sense of "location.”… "looking at" or "going to" a particular place to attend to the experience.
- consistent and generic
- memorable.
- laden with affect.
… Synesthetes often reported that they were unaware their experiences were unusual [unless new or] until they realized other people did not have them... Most report that their experiences are pleasant or neutral, although, in rare cases, they report that their experiences can lead to a some sensory overload (confusion.) ... Most report it as a gift—an additional "hidden" sense—something they would not want to miss. Most become aware in their childhood. Some apply this in daily life ... Synesthesia can occur between nearly any two senses [Sound->sight] or perceptual modes. ... Sound → color synesthesia … voice, music, and environment sounds such as clattering dishes or dog barks [or thunder storms?] trigger color and simple shapes that arise, move around, and then fade when the sound ends. Sound often changes the perceived hue, brightness, scintillation, and directional movement… People rarely agree on what color a given sound is. .…. groups say that loud tones are brighter than soft tones and that lower tones are darker than higher tones [i.e. can form textures in the reflections from complex material and surfaces]
=> An editor of this document experienced near-ultrasonic sound-vibration induced ‘location-synesthesia triggered by “lost” cries of three puppies, of a Border Collie puppies litter.
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