This page is a mishmash - hodgepodge of information on rabbit and some human vision.
"A rabbit has total field of view of the 60 degrees, to 20 degrees for each eye, with only 30 degrees of binocular field in front and 10 degrees behind the head." - Source.
Source image here.
Video segment about a rabbit's vision from "What is a rabbit..." by Dr. Anne McBride
"A Rabbit's Point of View | What Rabbits See" by Amanda Gullickson(MyPets1031)
Source image here.
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"Dichromacy (di meaning 'two' and chroma meaning 'color') is the state of having two types of functioning color receptors, called cone cells, in the eyes. Organisms with dichromacy are called dichromats. Dichromats can match any color they see with a mixture of no more than two pure spectral lights. By comparison, trichromats require three pure spectral lights to match all colors that they can perceive." - Wikipedia.
"Trichromacy or trichromaticism is the condition of possessing three independent channels for conveying color information, derived from the three different cone types. Organisms with trichromacy are called trichromats. The normal explanation of trichromacy is that the organism's retina contains three types of color receptors (called cone cells in vertebrates) with different absorption spectra. In actuality the number of such receptor types may be greater than three, since different types may be active at different light intensities. In vertebrates with three types of cone cells, at low light intensities the rod cells may contribute to color vision, giving a small region of tetrachromacy in the color space. - Wikipedia.
Rabbit's eyes are strategically located on the side and upper part of their head. They are lateral eyed animals. This allows them to have an almost 360 degree view
of world and to maximise their field of view. They can watch for movement from the top, sides and to some extent what's to the rear in "2D". They have a small blind spot in front of their nose, under their chin and directly behind them. This small blind spot prevents any real "3D" viewing of things that are close. They have depth perception a bit farther out (foward) helping them elude danger. Research shows that rabbits are protanopic animals, "a form of colour blindness characterized by a tendency to confuse reds and greens and by a loss of sensitivity to red light". Where humans have cones to see red, green & blue - rabbits do not have the types of cones that are sensitive to see the color red.
Rabbit's Vision:
Lateral eyed animals. Eye on each side of head & slightly above the midline
Visual field of nearly 360 degrees for a few breeds that have the same body type as a true wild European rabbit, Oryctolagus cuniculus.
Monocular - Two wide angles of view with eyes "2D"
Binocular - Narrow field of view with some depth perception
A few blind spots
'Limited' near vision but sensitive to movement.
Hyperopia, aka farsighted/longsighted (difficulty focusing on near objects) - opposite of Myopia (nearsightedness/shortsighted)
Horizontal area of high photoreceptor density - concentrate on all points of the horizon at one time
Don't have standard concentric types of ganglion cell, they have 'brisk-transient' & 'brisk-sustained' cells
Protanopic animals. Color vision
Dichromat. Can see combinations using two colors (green [520nm] & blue [425nm])
Reduction of color axes in red and yellow parts
Most likely rabbits don't see colors the same as humans. They do see many of the same color-wavelengths combinations and can tell many of them apart.
Retina (Fovea Centralis not indented)
Cones detect color under well-lit conditions (photopic vision). Rabbits have about 18,000 per sq. mm at peak density. About 10x less than humans.
Rods detect less detail & no color, but they are much more sensitive to light (scotopic vision). Rabbits have about 300,000 per sq. mm. at peak density. About 2x the amount of humans.
Majority of retina has green sensitive cones - Small area with no green but many blue cones.
Densities of photoreceptors vary systematically, depending upon the size of the eye and age of the rabbit
Acuity & Light - Crepuscular: see best at dusk and dawn
Rabbit's optics are better than those of many primate species.
Rabbit's have a higher ratio of rods than cones. Allow the rabbit to see in dim light situations
Rabbit's eye is eight times more sensitive to light then a human eye
Can not see well with very bright & very low light.
Fovea Centralis (Minuscule cone-shaped depression in the retina) not indented - less resolution.
No Tapetum Lucidum - a reflective structure that lies beneath the retina, acts like a mirror; reflecting light back through the retina increasing the light available to the photoreceptors. Same as humans.
Rabbits vision is somewhat grainy (vs humans)
Albino rabbits
Lack pigment in their iris & choroids, gives a ruby'ish reflection from within the eye
Some albinos will tend to do more "scanning", both ruby (REW) & blue (BEW) albinos
Development & Other Issues
Rabbits are born with their eyelids closed
They will normally open their eyes at about 10 days
What can they see? Field of view.
"We rabbits don't have the same vision you humans have, but ours works well for us. We see best in dim light - an advantage for wild rabbits, because they are most active at dawn and dusk. In bright light, you look grainy to us. We're farsighted, which helps us recognize predators before they get near. When you're close to us, you look blurry. We have a small blind spot in front of the nose and below the chin, so we can't see a treat placed there. Another difference between us is our depth perception. You humans have good depth perception- which makes you successful predators - because both your eyes face foward, and their visual fields overlap. On the other hand, my wild ancestors were prey animals, so survival depended on spotting danger coming from any direction. That's why we rabbits evolved eyes on both sides of the head, giving us a field of vision of almost 360 degrees. However, because our visual fields do not overlap, we have poor depth perception. We make up for it by interpreting subtle clues, just as you humans do when you watch television. For Instance, we perceive a larger object to be closer than a smaller one. We rabbits have one more technique to determine distance: head bobbing. When I bob my head up and down, objects close to me appear to move more than distant objects. So you see. Roscoe probably recognizes you more by your shape, movemet and voice than the details of your face." -
Veterinarian Dr. Lee Pickett V.M.D (writing for Reba Rabbit) responding to a question in his column 'Ask the vet's pet' in the Reading Eagle newspaper on September 13, 2006 [Source]
"Rabbits have poor vision up close, so they tilt their head to the side to help them see better in these situations.
Rabbits will also stand up on their hind legs to get a better look at what's going on around them. They can be very curious."
- University of California (@ Davis) Agriculture and Natural Resources -What Does
It Mean to Be a Rabbit?.
"Rabbits don't have very good depth perception... What allows us humans to concentrate on an object is an increase in cones in an area called the fovea in our eye. Rabbits have a similar area that spans 30% in front of their face, but has less cones than our eyes. However, remember, 10% of this space is a blind spot so rabbits only have depth perception in 20% of their field of vision. To make up for this lack of depth perception, rabbits use the technique called “parallax.” The bun bobs her head up and down. An object that moves more than other objects will be closer." -
House Rabbit Network -Q & A page.
"Prey animals such as rabbits have a wide angle of view" - "but lack binocular vision in all but a small part of their viewing range. They can see a lot of area but lack depth acuity." - here.
"Prey, on the other hand, generally have eyes situated more to the sides and top of the head. This position allows them excellent peripheral and upward vision. Because prey animals are often attacked from above, behind, or the side, it is advantageous for them to have this wide visual field, even if they cannot see well in front of their faces." - Pet Education.com.
"In contrast plant-eating prey animals like the rabbit and deer need to have a wide panoramic view so they can see predators approaching. They therefore have eyes placed on the side of the head, each with its own field of vision. They have only a very small area of binocular vision in front of the head but are extremely sensitive to movement." - Wikibooks.org
"Two Eyes to the Side - Nature has given animals the physical attributes necessary for survival. Lateral placement of the eyes is essential to the survival of hunted animals or herbivorous animals (e.g., horse, rabbit, cow) as it allows them to increase side or peripheral vision. Side vision (increased by lateral placement) is a sensitive detector for motion or movement. Peripheral vision allows creatures to effectively scan for danger. The rabbit must be constantly aware of its natural enemies while it eats your garden greens. At the first sign of danger, peripheral vision, the motion detector system, alerts the rabbit that there is danger. The immediate reflexive response is for the rabbit to run." - strabismus.org
"Rabbits have large, prominent eyes that are positioned on the side of the head with a cornea that occupies approximately 25% of the globe. These features give rabbits a visual field of nearly 360 degrees. However, despite their wide vision, accommodation is poor. The lens is large and spherical and the ciliary body{"The ciliary body is the circumferential tissue inside the eye composed of the ciliary muscle and ciliary processes"} poorly developed (Bagley and Lavach, 1995). The retina has a horizontal area of high photoreceptor density, the visual streak, that allows the rabbit to concentrate on all points of the horizon at one time, enabling it to be aware of a predator coming from any direction (Williams, 1999). Rods are the predominant photoreceptor cells and rabbits have
good nocturnal vision (Bagley and Lavach, 1995)." - Textbookof RabbitMedicine revised and updated byMolly Varga, 2e2014, Buy ebook.
"The rabbit is a prey animal, which means that in the wild it needs to have all-round vision so that it can see if it is about to be attacked. For this reason the eyes are sited towards the top of the head and each eye has a 190-degree field of vision. Rabbits are also very long-sighted. However, the position of the eyes means that the rabbit is not able to see directly in front of its nose, and if a hand approaches its face from directly in front, it may attack out of fear. For this reason rabbits should be approached from above so that they can see what is happening." - Rabbitlopaedia: A Complete Guide to Rabbit Care; p65. buy book.
"The eyes are designed for long-sighted use and have limited near vision." - rabbitrehome.org.uk.
"Among non-primate mammals, the coding of visual stimuli has
been particularly well-studied in the rabbit [19-23]. Rabbits have large eyes, with optics better
than those of many primate species. Their retinas do contain
the standard concentric types of ganglion cell, in the rabbit
termed 'brisk-transient' and 'brisk-sustained' cells. However,
these standard cells make up less than one quarter of all the
retinal ganglion cells, which are distributed among ~12 anatomical
and functional types [14,21]. It is
now clear that each of these 12 types is tuned to a distinct feature
of the visual input, along the lines shown in
Figure 1. The importance of this fact is that the rabbit's brain
must receive a preponderance of non-standard visual signals. This
information is not new: what is new is the evidence that most or
all mammalian retinas transmit a diversity of visual codings to the
brain [4,13,24,25], and that this diversity should be incorporated
into any realistic view of how vision works." - Current Biology, Vol 17 No 15, The unsolved mystery of vision, Richard H. Masland
and Paul R. Martin, R578-R579
"A second non-standard cell type (identified thus far in rabbits,
cats, and mice) is the so-called local edge detector." - "The local edge detectors appear
to be the most numerous type of retinal ganglion cell in the rabbit,
but they have not been included in the standard view of the visual
system. Could these cells form a system for long-range movement
analysis? How does the visual cortex process the signals from
these cells? How many other mammalian species sample the
world with both the standard brisk sustained cell, and also the
local edge detector - or even with codings that remain to be
discovered?" - Current Biology, Vol 17 No 15, The unsolved mystery of vision, Richard H. Masland
and Paul R. Martin, R579-R580Depth Perception - Binocular Vision
"There are other ways to gauge distance, and rabbits may use these. One is to pick up on subtle visual cues, similar to the ones we notice when we watch a three dimensional scene on a two dimensional television screen. These include size differences between objects and the blurring of far away objects." - Three Little Ladies.
"Because of the placement of the rabbits eyes, only about 30 degrees of their entire field of vision overlaps, and 10 degrees of that is a blind spot. The result is very little three dimensional viewing for the rabbit. Rabbits will use parallax to assist in determining distance of an object." - Wisconsin HRS. This is why they move their head when trying to get a better view.
"Rabbits can actually see 3-D objects, just not as well as us humans. Their vision field is almost 360 degrees due to the fact their eyes are located high on the sides of their head and slightly bulge out. They do have a blind spot of 10 degrees directly in front of their nose. Also, rabbits are farsighted. This enables them to see hawks flying above. Not useful for our indoor rabbits, but their eyes evolved from their outdoor ancestors." -
House Rabbit Network -Q & A page.
A study that looks at the binocular vision in the rabbit reports that rabbits have binocular vision. Abstract form the paper: "Two experiments are reported where rabbits were trained on both an Either- Or and a Same-Different visual discrimination task. A system of coloured patterns and light filters ensured that information was accessible only by binocular vision. The results showed that the animals were able to solve both types of discrimination problems under these conditions." - Binocular vision in the rabbit; Physiol Behav. 1977 Jul;19(1):121-8; Van Hof MW, Russell IS - [Abstract]
"Some domestic breeds have the shape of their head altered from that of the natural design, and so the eyes may offer more or less binocular vision, depending on where they are - Lionhead breeds, for example, have eyes that are more forward facing than the natural design - it would be safe to assume that they may well have increased binocular vision." - Hopping Mad! Bunny magazine, @ yahoo answers
"The degree of specialization required of the temporal area centralis or fovea will obviously depend upon such species-specific factors as the distance at which binocular vision is normally used and the size of the targets to be detected.
For these reasons, the increase in density there may not be dramatic and escape attention without special
techniques, as in the case of the rabbit. The low degree of specialization in its temporal area is perhaps related
to the low demands placed upon the rabbit's need for binocular vision as it feeds on targets at very close range
with a consequent larger angular target size and retinal disparity. In rabbits, the temporal area specialization
is limited to one cell class which, in ordinary preparations without special labelling, tends to be
overshadowed by the high density of neurons in the monocular, central retina (Provis, 1979)." - Pettigrew, J.D. (1986) Evolution of Binocular Vision. In Visual Neuroscience, eds. J.D. Pettigrew, K.J. Sanderson and W.R.Levick pp 208-22. Cambridge University Press.
"Binocular vision in the rabbit: The rabbit forms a convenient counterpoint to
other mammals since it was long considered that functional binocular vision was not a feature of its visual
system. Indeed the rabbit, like many birds, can eliminate its frontal region of functional binocular
overlap by the appropriate oculomotor posture, such as the one it adopts when in the freeze position (Hughes
it Vaney, 1982). Recent work has shown, however. that rabbits do converge their eyes wheat feeding (Zuidam &
Collewijn, 1979) and that there are binocular neurons in the visual cortex which have most of the properties
enumerated above to indicate that they are involved in functional binocular vision. For example, these
binocular neurons have orientation selectivity which is tightly matched for both receptive fields (Hughes &
Vaney, 1982). Previous work had failed to demonstrate this nice selectivity, which is matched on both retinas,
and even led to the suggestion that the binocular connections of the rabbit might be maladaptive (Van
Sluyters it Stewart, 1974). The conclusion that the binocular fields were not matched may well have been
based upon inappropriate eye position, or failure to correct the eccentric optics of the rabbit, or both, and
this serves as a good example of the need to establish optical and eye position parameters in any species for
which binocular vision is being investigated (cf. the long line of baseline investigations of the cat's optics
and binocular test position of the eyes carried out by Peter Bishop during his career)." - Visual Neuroscience edited by John Douglas Pettigrew, Kenneth James Sanderson, William Russell Levick. (1986) pp 212-13. Cambridge University Press.Color?
In this abstract from a paper titled The perceptive color space of the rabbit, they
summarize that "The four-dimensional spherical structure of perceptual color space was obtained, which was different from that of trichromatic species in a reduction of color axes in red and yellow parts. The evidence characterizes rabbit as a protanopic animal." - Zh Vyssh Nerv Deiat Im I P Pavlova. 1998 May-Jun;48(3):496-504., [Article in Russian], Polianskiĭ VB, Sokolov EN, Marchenko TIu, Evtikhin DV, Ruderman GL.
One definition of protanopic is "a form of colour blindness characterized by a tendency to confuse reds and greens and by a loss of sensitivity to red light" - Reverso.net.
"Two kinds of light-sensitive cells-cones and rods-are found in the retina of lagomorphs, people, and other mammals. Cones detect bright light, and the pigments they possess provide the ability to see color when hit by light of different wavelengths. Rods activate under low light and lack the pigments that produce color vision. In the domestic European rabbit, the only species studied, rods dominate the retina, where rods reach a peak density of about 300,000 per square millimeter in contrast to cones' peak density of about 18,000 per square millimeter. These cones are sensitive to either green or blue light, but not to red, so rabbits are limited to what is called dichromatic (two-color) vision. Most of the retina is dominated by green sensitive cones, but there is a small area with no green cones and many blue cones. What this may mean for rabbits' color vision is unknown, but the cones would allow rabbits to see over a narrow range of wavelengths during the day. Rabbits don't seem to pay much attention to color though." - Rabbits: The Animal Answer Guide, p55, by S. Lumpkin & J. Seidensticker - buy ebook.
Human Eye
Rabbit Eye
Cones: "Cones detect color under well-lit conditions and are densely packed in the fovea, near the center of your retina. Cones help you see color and fine detail, which is why you look directly at objects you want to see well, like books, movies, and faces." - OMA
"Cones are active at higher light levels (photopic vision), are capable of color vision and are responsible for high spatial acuity." - cis.rit.edu
"Rabbits, too, have small retinal areas with more cones than rods. However, this area centralis is not indented, and it has far lower cone density than our fovea has. The image formed by the area centralis is relatively "grainy" compared to the one formed by your fovea, but it serves the rabbit well." - H.A.R.E.
The maximum concentration of cones is roughly 180,000 per sq. mm in the fovea region and this density decreases rapidly outside of the fovea to a value of less than 5,000 per sq. mm. - reference
Cones' peak density of about 18,000 per sq. mm.
Rods: Rods are mostly away from the center of your retina. You see less detail and no color with the rods, but they are much more sensitive to light." - OMA
"Rods are responsible for vision at low light levels (scotopic vision). They do not mediate color vision, and have a low spatial acuity." - cis.rit.edu
Average 80-100,000 rods sq. mm. Rods peak in density in a ring around the fovea at 160,000 rods per sq. mm. -
reference
Rods reach a peak density of about 300,000 per sq. mm.
"... we have found that densities of photoreceptors vary systematically, depending upon the size of the eye and age of the animal. In 'standard' New Zealand rabbits of 2-3 kg (2-3 months old), rods reached a peak density of about 300,000/mm2 just dorsal to the visual streak, while cones exhibit peak density at mid-visual streak of about 18,000/mm2. Published measurements of visual acuity in rabbit are less than predicted by this calculation. The ratio of cones to rods is significantly higher in ventral retina, where the density of cones declines to a plateau of 10,000-12,000/mm2, when compared to dorsal retina, where cones are uniformly distributed at a density of about 7000/mm2. The density of OS-2 labeled (presumably 'blue') cones is uniformly low, 1000-1500/mm2, in a wide expanse that includes dorsal retina, the visual streak, and much of ventral retina, except for a region of higher density along the vertical midline. We confirm that there is a far ventral horizontal region near the perimeter that is populated exclusively by a high density (about 13,000/mm2) of OS-2-positive cones (Juliusson and colleagues)." - Regional topography of rod and immunocytochemically characterized 'blue' and 'green' cone photoreceptors in rabbit retina, E. V. Famigliettia & S. J. Sharpea, Visual Neuroscience / Volume 12 / Issue 06 / November 1995, pp 1151-1175
"Some studies have shown that rabbits can discriminate between blue and green. Rabbits eyes are like dogs eyes in this respect. However, how the rabbit's brain interperts this difference may be different than how we humans discriminate between different colors." -
House Rabbit Network -Q & A page.
"The retina of your eye has two types of light-detecting cells: rods and cones. Cones detect color under well-lit conditions and are densely packed in the fovea, near the center of your retina. Cones help you see color and fine detail, which is why you look directly at objects you want to see well, like books, movies, and faces. Rods are mostly away from the center of your retina. You see less detail and no color with the rods, but they are much more sensitive to light." - One Minute Astronomer
A research paper studying Coding of Luminance and Color Differences on Neurons in the Rabbit's Visual System they looked at "The neuronal activity in the rabbit's visual cortex, lateral geniculate nucleus and superior colliculus was investigated in responses to 8 color stimuli changes in pairs." Please rembember this is a scientific research paper.Abstract; Paper - Evtikhin, Dmitry V.; Polianskii, Vladimir B.; Alymkulov, Dzekshen E.; Sokolov, Evgenii N.. (2008). Coding of Luminance and Color Differences on Neurons in the Rabbit's Visual System. The Spanish Journal of Psychology, . 349-362.
Color Vision in Mammals
"Recent molecular phylogenetic analyses of mammals based on much more extensive data sets strongly suggest that (1) cat, goat, and deer are closely related with each other; (2) rabbit appears to be closely related to primates; (3) guinea pig clusters with cat, goat, deer,
and rabbit; and (4) mouse, rat, and squirrel are most distantly related."
"The results at the organismal level suggest that the evolutionary relationship of the mammalian pigments is best
represented by (((human, rabbit) ((((deer, goat), dolphin), horse) cat)), guinea pig), ((mouse, rat), squirrel)."
"A composite tree topology of the mammalian red and green pigments and
ancestral amino acids at sites 180, 197, 277, 285, and 308. The numbers after P refer to l max values obtained from the
in vitro assays, whereas the numbers beside branches are predicted values from the five-sites rule. The ancestral amino
acids that have a probability of 90% or less are underlined.
The rectangles indicate amino acid substitutions. In the estimation, the red pigments of
American chameleon (U08-131) and chicken (M62903) were also used as the outgroup."
- The Molecular Genetics of Red and Green Color Vision in Mammals by
Shozo Yokoyama and F. Bernhard Radlwimmer, 1999, P921 & P927 [Above information & chart]
Acuity/Resolution & Sensitivity to Light?
"In the human eye there is an area called the centralis, which is slightly indented. Rabbits also have this area, however, in rabbits this area is not indented. The result is that rabbits vision tends to be somewhat grainy." - Three Little Ladies Rabbitry.
"The optic disc has a physiologic cup and the eye does not have a tapetum lucidum, similar to pigs, guinea pigs, primates, and birds (Ollivier et al., 2004)."
- The Laboratory Rabbit, Guinea Pig, Hamster, and Other Rodents edited by Mark A. Suckow, Karla A. Stevens, Ronald P. Wilson, pp 196-97 (2012)
"Pigs and rabbits don't have tapetum lucidum." - Bulletin UASVM, Veterinary Medicine 65(2)/2008, pISSN 1843-5270; eISSN 1843-5378,
MORPHOLOGICAL ASPECT OF TAPETUM LUCIDUM AT SOME DOMESTIC ANIMALS
"Some animals have neither an apparent fovea, nor even a differential distribution of photoreceptors, and possess a relatively low acuity (e.g., rabbit)...." - Springer Reference
"As you read this page, you are focusing on the letters with a very tiny part of your retina called the fovea. This is a minuscule, cone-shaped depression in the retina, lined wall-to-wall with high resolution cone cells." - "Rabbits, too, have small retinal areas with more cones than rods. However, this area centralis is not indented, and it has far lower cone density than our fovea has. The image formed by the area centralis is relatively "grainy" compared to the one formed by your fovea, but it serves the rabbit well." - H.A.R.E. by Dana M. Krempels, Ph.D., "What Do Rabbits See?"
"The other item that assists in vision are called rods. Rods assist us in seeing clearly and in seeing in low light situations. Rabbits have a higher ratio of rods than cones. This would allow the rabbit to see in dim light situations. However, rabbits also have no tapetum, which is what many animals use for night vision. Combined these two would indicate that the rabbit can see well when they are most active, dawn and dusk, and cannot see well at night." - - Three Little Ladies.
"The eyes are designed for long-sighted use and have limited near vision. The Pupils have a limited contraction capacity therefore they see well in dim/dull conditions. Bright light restricts their vision and intense light can lead to temporary blindness. A Rabbit's eye is eight times more sensitive to light then a human eye. Surprisingly Rabbits do not have good night vision. The eye does not have a Tapetum, the structure that acts to amplify light that has entered the eye. A Rabbit will see the world as a "grainy" picture." - rabbitrehome.org.uk.
"Intense light blinds a rabbit, as he has restricted contraction of his pupils." - "Sunset is the optimal time of day for a rabbit to see."
- justrabbits.com.
Pigmented rabbits have roughly 20/240 (Snellen) or 1.1 (LogMAR) visual acuity. The study "Ocular refraction and visual contrast sensitivity of the rabbit, determined by the VECP.", pointed to a pigmented rabbit having a CSF (contrast sensitivity function) that peaked at 0.35 cpd (cycles per degree), with visual acuity of 3 cpd. "The grating acuity of the wild European rabbit.", measured the visual acuity of wild the European rabbits from 1.6 to 2.5 cpd. Taking 2.5 cpd, and using Ulster University's "Snellen fraction conversion chart" (Snellen/LogMAR/cpd), you get an approximated 20/240 Snellen value. Formula for convert Snellen units to cycles per degree: Visual Development, Diagnosis, and Treatment of the Pediatric Patient & Diagnostic Procedures in Ophthalmology.
3rd Eyelid - Nictitating membrane WORK IN PROGRESS
"The nictitating membrane (from Latin nictare, to blink) is a transparent or translucent third eyelid present in some animals that can be drawn across the eye for protection and to moisten it while maintaining visibility. Some reptiles, birds, and sharks have full nictitating membranes; in many mammals, a small, vestigial portion of the membrane remains in the corner of the eye." - Wikipedia.
"One point to mention about the rabbit eye, although it does not pertain directly to vision, is the function of the "third eyelid." Many animals, from amphibians to birds to mammals, possess this structure, known as a nictitating membrane. The primary role of the third eyelid is to protect the eye against injury. And people with albino rabbits, whose light eyes make the membrane very visible, will tell you that the membrane comes down over the eye when the bunny is frightened. In the rabbit, the third eyelid also helps keep the eye moist, which may explain why rabbits only blink 10 to 12 times an hour." - Wisconsin HRS.
"Rabbits are born with their eyelids closed. Separation of the eyelids occurs at about 10
days of age. The upper eyelid is shorter, thicker, and more mobile than the lower lid. Rabbits blink approximately 10-12 times per hour (Peiffer et al., 1994). A third eyelid is
present that does not actively nictitate but passively covers the cornea as the globe is
retracted. It does not move more than two-thirds of the way across the cornea." - Textbookof RabbitMedicine revised and updated byMolly Varga, 2e2014, Buy ebook.Albinism - Eyes & Scanning
Albinism is a decrease in or absence of melanin, the protein necessary for pigmentation. This typically affects the skin, hair and eyes.
"Vision. Melanin helps develop various parts of the eyes, including the irises, retinas, eye muscles, and
optic nerves. The absence of melanin results in disorganized development of eyes and leads to problems with focusing, depth perception,and tracking." -
Albino Animals
You can have a albino with either ruby/red, light blue, or pink. You can also see other colors with a "Ruby cast" to the eyes. These rabbits seem to do more "scanning."
To help with determining the distance of an object some rabbits use parallax to help with this. Moving their heads from side to side to help judge distance. It seems that some albino rabbits can do this to a greater degree.
"In Dwarfs, there are two distinct and separate types of albinism. The first is the Ruby-Eyed White gene, found on the c series, which causes complete melanin restriction in fur, eyes, nails, and every other part of the body. This form of albinism can also restrict color to a greater or lesser extent across the body when it is found in a single allele on the c series. Blue-Eyed White is a form of incomplete albinism caused by the restriction of melanin across the majority of the body." - 2006 Spring issue of the Dwarf Digest written by Jennifer Poeschl.
"Some rabbits have an odd behavior called "scanning." It seems to be most prevalent in albino rabbits, but no one knows why. It may be an exaggerated motion associated with the normal nystagmus of the eyes. -- Nystagmus is the natural, microscopic movement that every vertebrate eye makes constantly--including ours! It's what makes vision possible. As our eyes microscopically change the visual field at this tiny level, constantly (we are not aware of it, and you can't see or feel it), the eye's photoreceptors are constantly stimulated by the ever-changing light hitting them. This is why we can see. Without nystagmus, we would not be able to see.
-- Some people have suggested that albino rabbit "scanning" (the side to side movement of the head you're seeing) is an "outgrowth" of normal nystagmus--but no one knows for sure. -- But the bottom line is that it's a genetic trait that is not harmful, and it's nothing to worry about." - August 8th, 2007 reply @ allexperts.com by Dana M. Krempels, Ph.D. (of HRS & H.A.R.E.)
"Scanning" or "tracking" is a vision-related rabbit behavior that can cause concern in those unfamiliar with it. Some rabbits will sit and weave or sway slowly back and forth. They appear to be causing motion in order to see an object that is within a short distance of themselves. This behavior is also observed when carrying a rabbit facing forward. Head motion is thought to be a means of enhancing distance measurement. When the eye is moving, close objects move faster than distant ones." - "If your rabbit is a scanner--most common in pink-eyed rabbits--she will regularly scan; it won't be a sudden-onset behavior. As with so many other aspects of rabbit behavior and health, sudden changes indicate health problems."
-- NOTE: -- "IS IT A STROKE? If your rabbit, especially an older rabbit, suddenly appears unstable, disoriented with eyes that "twitch," it's very important to note whether the eyes are moving up and down or back and forth." - "This eye twitching is called nystagmus. Up and down eye movement signifies a brain problem, whereas back and forth signifies an inner ear infection or other problem. In either case, the rabbit needs to get to her veterinarian as soon as possible." - sandiegorabbits.org - San Deigo HRSProblems:
"Deafness is a common side affect in blue-eyed albinos across all mammalian species. The genes that restrict the melanin production seem to be closely linked to the genes that affect hearing." - themadhattersrabbitry
"This animation is an example of parallax. As the viewpoint moves side to side, the objects in the distance appear to move slower than the objects close to the camera."
Source image here.
Rabbit Eye Colors
image source
This meme sums up a rabbits hyperopia best.
"This animation is an example of parallax. As the viewpoint moves side to side, the objects in the distance appear to move slower than the objects close to the camera."
Source image here.
Below are visual examples of how color blindness can effect human vision. They are here for an example.
Most likely rabbits don't see colors the same as humans. They do see many of the same color (wavelengths) combinations and can tell many of them apart.
"A rainbow of colors as viewed by a person with no color vision deficiencies."
Source image here.
"The same rainbow as viewed by a person with protanopia."
Source image here.
"Protanopia Color Spectrum"
Source image here.
"Human Eye"
Source image here.
"Cones & Rods"
Source image here.
"The retina is the nervous layer of the eye and contains the light receptors. Axons from these nervous cells converge toward the back to form the optic nerve. It is thus named the blind spot or optic disc. Facing opposite of the pupils is an area of maximum concentration of cone receptors. This area, the macula lutea of the fovea centralis has the best vision."
Image & information source here.
Human cone shaped depression in the retina - Fovea Centralis.
Image source here.
Tapetum Lucidum: "The tapetum is a reflective structure that lies beneath the retina. It acts like a mirror; reflecting light back through the retina. Animals that are active at night have a tapetum. Dogs, Cats, Horses, and Cows all have tapetums. It causes the yellow or green glow you see when light hits an animal's eyes." - Source.
"In humans, eye color is determined by the amount of light that reflects off the iris, a muscular structure that controls how much light enters the eye. The range in eye color, from blue to hazel to brown (see figure one), depends on the level of melanin pigment stored in the melanosome 'packets' in the melanocytes of the iris. Blue eyes contain minimal amounts of pigment within a small number of melanosomes. Irises from green–hazel eyes show moderate pigment levels and melanosome number, while brown eyes are the result of high melanin levels stored across many melanosomes (see figure two, left)." -
pic & text source here.
