A cat's eyes are among the most expressive features of its face, and they are also delicate instruments worth protecting. In Cats (Felis catus), vision is built for low light rather than for color, with a reflective tapetum lucidum behind the retina and roughly six times a human's sensitivity in dim conditions. The same design carries a cost: cats see blues and greens through dichromatic eyes but not reds, and the eye's dependence on clear corneas, controlled pressure, and steady tear film leaves it exposed to a short list of well-understood diseases. Because most feline eye problems announce themselves at the surface, in pupil size, tear staining, squinting, or the position of the third eyelid, an owner who learns a five-second daily glance is positioned to catch trouble while it is still small.
The Healthy Eye and Its Checks
A bright, clear gaze with symmetrical pupils is the baseline any owner can learn in a week. The corneas should be glass-smooth and free of cloudiness, the whites of the eyes should stay white without redness, and the two pupils should match each other in size in ordinary light and shrink together when a lamp moves closer. Both eyes should sit level in the face and track movement together, a quick test performed by dragging a toy across a cat's visual field and watching both eyes follow in unison.
The Third Eyelid
Cats carry a third eyelid, the nictitating membrane, that normally rests hidden at the inner corner of each eye. It rises to protect the surface during sleep, deep rest, and certain illnesses, so a membrane that stays visible in a wide-awake cat is information rather than a curiosity. A raised third eyelid can accompany eye pain, corneal injury, dehydration, fever, or the general misery of systemic disease, and persistent elevation on one or both sides belongs on a veterinary visit.
Tears, Discharge, and Grooming
The tear film should keep the surface wet without leaving much trace. A faint amount of clear or slightly rust-colored crusting at the inner corners, wiped away with a damp cotton pad once a day, is ordinary, particularly in breeds with shortened faces where tears cannot drain cleanly. What is not ordinary is discharge that is thick, yellow, or green; tears that overflow down the face all day; or one eye that waters while the other stays dry. Cats groom their own faces thoroughly, and a cat that suddenly stops washing around the eyes, or paws at them, has changed its behavior for a reason worth checking. Vision in dim light can be quietly tested at home by watching how confidently the cat navigates an unlit hallway at night, since the tapetum that makes cat eyes shine in headlights also lets them move through darkness a human could not manage.
Eye Signs That Need Urgent Care
Squinting is one of the clearest pain signals the feline eye can send, and it almost always points to the cornea. A cat holding one eye shut, blinking rapidly, or rubbing at a closed eye is usually reporting a corneal ulcer, an erosion of the clear front surface caused by trauma, a scratch from another cat, a foreign body, or a herpesvirus flare. Ulcers deepen quickly in cats, and a shallow scratch treated promptly can become a descemetocele, a near-perforation of the cornea, in days. Fluorescein staining at the clinic confirms the diagnosis in seconds, and treatment started early protects sight. Squinting never waits for a scheduled appointment.
Glaucoma: The Cloudy, Enlarged, Painful Eye
Glaucoma, a dangerous rise in pressure inside the eye, is less common in cats than in dogs but equally punishing when it arrives. The signs assemble into a pattern: the eye grows cloudy or bluish, the globe itself may appear enlarged, the pupil may not respond to light, and the cat is visibly painful, often hiding, sleeping more, and eating less rather than pawing at the eye the way a dog might. Feline glaucoma is usually secondary to other disease, uveitis, lens displacement, or an intraocular tumor, and pressure must be measured with a tonometer to confirm it. An untreated glaucomatous eye goes blind and stays painful, so a cloudy, enlarged, uncomfortable eye is same-day business.
Sudden Vision Loss and the Proptosed Eye
Vision that vanishes over hours, a cat that walks into furniture, misses jumps it has made for years, or startles when approached, points to sudden acquired retinal degeneration, retinal detachment, advanced hypertension, or glaucoma. Blood pressure measurement is central here, because hypertension driven by kidney disease or hyperthyroidism, two members of the senior trio, is one of the leading causes of abrupt blindness in older cats, and the retinal changes it produces are visible on examination. The most dramatic ocular emergency is the proptosed eye, a globe displaced forward out of the socket, usually after severe trauma such as a car strike or a fall. The eye sits exposed, drying by the minute. It is wrapped in a wet cloth, the cat is kept calm, and the trip is immediate; prognosis depends heavily on how quickly the eye is replaced and restored to moisture.
Common Chronic Eye Conditions
Conjunctivitis, inflammation of the pink tissue lining the lids and covering the front of the globe, is the most frequently diagnosed eye problem in cats. The conjunctiva reddens, swells, and produces discharge that ranges from watery to purulent, and both eyes are often affected together. Infectious causes dominate in cats, with feline herpesvirus type 1 and Chlamydia felis at the top of the list, and young cats in multi-cat settings are the classic patients. Treatment is topical or systemic medication aimed at the cause, and diagnosis matters because the treatments differ.
Cherry Eye
The gland of the third eyelid, which produces a large share of the tear film, can prolapse from its normal position and appear as a red, rounded mass at the inner corner, the condition called cherry eye. It is uncommon in cats but unmistakable when present. Because that gland cannot be spared, the repair is surgical repositioning rather than removal; excising the gland leaves the eye short of tears for life and sets up dry eye later.
Cataracts Versus Nuclear Sclerosis
Lens changes in aging cats split into two categories with very different consequences. Nuclear sclerosis, a normal graying and hardening of the lens center, gives the pupil a faint bluish cast in middle age and onward but costs little functional vision and needs no treatment. A cataract, by contrast, is an opacity of the lens fibers, white rather than gray, that blocks light on its way to the retina. Cataracts are less common in cats than dogs but appear with diabetes, chronic uveitis, inherited disease, and trauma, and a dense cataract can be surgically replaced. Distinguishing the two is a five-minute examination, and the difference is the difference between reassurance and a treatment plan.
Dry Eye and Herpesvirus Flares
Keratoconjunctivitis sicca, usually shortened to KCS or dry eye, arises when tear production falls short of the surface's needs. The eye looks dull and tacky, collects tenacious mucus, and becomes vulnerable to chronic corneal irritation and pigment. Dry eye is rarer in cats than dogs, often following herpesvirus damage to the tear glands, and it is confirmed with a Schirmer tear test that measures tear output in millimeters per minute. Herpesvirus itself deserves its own mention: the vast majority of cats carry feline herpesvirus type 1, acquired in kittenhood, and the virus settles into nerve tissue and reactivates with stress, illness, or corticosteroid exposure. A herpes flare announces itself as red, watery, uncomfortable eyes, sometimes with corneal branching ulcers, and it resolves with supportive care and antiviral medication in severe cases. Flares tend to recur through life, so a cat with a known history benefits from low-stress routines and prompt attention at the first sign of redness.
Breed Eyes and Prevention
Face shape shapes the eye. Persians, Exotic Shorthairs, Himalayans, and other flat-faced breeds carry shortened skulls in which the eyes are prominent, the tear ducts are kinked, and the eyelids ride close to the cornea. The predictable results are tear staining that needs daily wiping, exposed corneas that dry and scar more easily, entropion, in which an eyelid rolls inward and lashes drag across the surface, and a higher rate of corneal ulcers. These cats are not doomed to eye disease, but their eyes need more maintenance: regular wiping of the facial folds, vigilant watching for squinting, and earlier veterinary thresholds than a long-faced cat requires.
Breed and Inherited Risks
Some ocular risks travel in bloodlines. Progressive retinal atrophy, a gradual inherited retinal degeneration that ends in blindness, occurs in several breeds including Persians and Abyssinians, and responsible breeders test breeding stock where tests exist. Entropion runs in families, eyelid agenesis, a congenital gap in the eyelid margin, appears in certain lines, and iris color itself carries no disease meaning beyond the blue eyes linked to deafness in some white cats. Knowing a cat's breed background converts these from surprises into expected checkpoints.
Prevention in Practice
Most serious eye disease in cats is caught, not prevented, but the catching can be engineered. Kittens should have their eyes examined during early vaccine visits, because eyelid adhesions, infections, and congenital defects respond best to early correction. Adult cats benefit from the daily glance described earlier, a check of symmetry, clarity, and discharge that takes seconds. Blood pressure checks at senior visits guard the retinas against the silent creep of hypertension, and keeping vaccinations current prevents the respiratory infections whose ocular complications, conjunctivitis and corneal ulcers, follow herpesvirus and calicivirus into households. Clipping sharp nail tips on indoor cats trims one of the more common causes of self-inflicted corneal scratches.
The Eyes in the Care Routine
A few seconds spent looking at a cat's face each day, plus a closer look during the weekly grooming session, folds eye care into a routine the cat already tolerates. The sequence is simple: compare the two eyes for size and clarity, note the amount and color of any discharge, confirm the third eyelid is hidden, and watch the cat navigate a dim room once in a while. Wipe the inner corners with a separate damp pad for each eye, moving inward to outward, and never use the same pad on both eyes when discharge is present. Any medicated drop or ointment prescribed for one cat stays with that cat, and treatment plans run their full course even after the eye looks healed, since stopping early is the fastest route to a recurring ulcer. Cats hide eye pain as efficiently as they hide every other kind, so squinting, a dilated pupil that will not shrink, or an eye held half-closed in a cat that claims to be eating and playing normally still merits a call. Eyes are among the few organs where decline, once advanced, cannot be reversed, and among the few where an owner's daily glance can move every diagnosis earlier, when treatment is shortest and sight is cheapest to keep.