Ever wonder what your feisty feline sees when he pounces on bugs or flanks birds at the windowsill? Most cats have good vision -- better than humans, in many respects. Their binocular eyes afford them excellent depth perception across short distances. Their long-distance and peripheral vision are poorer, though.
Hunters, Born and Raised
Most cats -- that is, most members of the Felidae family -- are deft hunters whose exceptional senses of smell, hearing and sight help them thrive on every continent except for Australia and Antarctica. Cats are excellent climbers who, unlike dogs, prefer to ambush their prey. As obligate carnivores, they have to eat meat to survive but they'll kill more prey than they can eat if given the opportunity. Domestic and feral cats (Felis catus) share all these traits. They're ubiquitous around the world and do especially well in cities. That's right, that cat basking in sunbeams near your desk is an urban assassin with killer eyesight.
My, What Big Eyes You Have
Cats see ultraviolet light and other lights that're invisible to humans; they open their vertical-slit pupils like saucers to draw in scant light at dawn and dusk; and they have a special layer of cells in their eyes called the tapetum lucidum that lights up near-darkness. Cats have excellent vision, and that's putting it mildly. There're a few catches, though. Long thought to be color blind, cats have poor color vision but can discern between several colors (but probably not 50 shades of grey). Cat eyes are delicate and minor injuries can blind them. Their third, partially translucent eyelids shield their eyes during fighting and across tough terrain. Cats are just as blind as humans in total darkness, too. That whole seeing-in-the-dark thing is an exaggeration. Your cat has corneas, pupils, iris, lenses, retina and optic nerves, just like you. His eyes are probably six times more sensitive to light than yours, though.
Near and Far
Cats' eyes are on the front of their head and thus duplicate images. This overlapping images cause depth perception. Healthy cats see 100 degrees to either side of center, about 45 degrees of which overlaps in both directions. Their sharpest vision is 2 to 3 feet from their faces, and they see things that pass across their vision better than things coming directly at or away for them. Cats' visual depth perception functions similarly to humans at close distances, perhaps even better. Long-distance and peripheral vision aren't their strong suits, though. Many prey animals have monocular vision. Their eyes are on the sides of their head, allowing them to keep tabs on a larger area, but without sense of depth. Cats, along with most predators, sacrifice field width for depth and better detect motion and gauge distances.
Eyes Wide Shut
Eye disease and vision loss are common in the cat world, particularly among middle-aged and elderly cats. Conjunctivitis, an inflammation of eyelid and eyeball tissues, is the most frequent eye problem in cats, according to a Cornell Feline Health Center primer. If treated early -- the primary symptom is teary eyes and swollen eye tissues -- it's easily cured. Cataracts, glaucoma, progressive retinal atrophy and tumors can all cause permanent, irreversible damage. Bacterial and fungal infections, feline immunodeficiency virus, feline leukemia virus, feline infectious peritonitis virus, feline herpesvirus, toxoplasma and cryptococcus can also harm your cat's eyes, gradually leading to blindness. If it looks like your cat is having trouble seeing, it's time to call a veterinarian.
- Animal Diversity Web: Felidae (Cats)
- Washington State University Extension: Cat Anatomy and Physiology
- Cornell University Cornell Feline Health Center: Feline Vision Problems -- A Host of Possible Causes
- S. Murray Sherman: Visual Development in Cats
- Animal Planet: Anatomy of a Cat -- Eyes and Vision
- VetInfo: Cat Vision -- What Cats See
- CatHealth: Feline Vision
- Kitty Show: Cat Color Vision
- The Smithsonian/NASA Astrophysics Data System: Selective Loss of Binocular Depth Perception After Ablation of Cat Visual Cortex
- Journal of Neurophysiology: Physiological Consequences for the Cat's Visual Cortex of Effectively Restricting Early Visual Experience With Oriented Contours
- Cornell University Cornell Feline Health Center: Sudden Blindness
- University of Missouri College of Veterinary Medicine: Cats' Eye Diseases Genetically Linked to Diseases in Humans
- PawNation: Seeing Eye to Eye -- Comparing Cat and Dog Vision
- Thinkstock/Comstock/Getty Images