Cats’ eyes can look “weird” for a surprising number of reasons, ranging from harmless age-related changes to conditions that need same-day veterinary care. The key is knowing which visual changes are benign and which signal a real problem. Here’s what different eye abnormalities actually mean.
One Pupil Looks Bigger Than the Other
Unequal pupil size, called anisocoria, is one of the more alarming things you might notice. One eye looks dilated while the other stays normal, or one pupil seems unusually constricted. This isn’t a condition on its own but a sign of something affecting the eye or the nerves that control pupil size.
The possible causes range widely. Glaucoma (elevated pressure inside the eye) can enlarge one pupil. Damage to or degeneration of the iris muscle can prevent it from constricting properly. Nerve lesions affecting the pathway between the brain and the eye are another possibility. In older cats, inflammation inside the eye (uveitis) is a common culprit. If you notice a sudden difference in pupil size, especially paired with squinting, cloudiness, or your cat bumping into things, that warrants a prompt vet visit.
A Cloudy or Hazy Look to the Eye
Cloudiness is probably the most common reason cat owners search for answers about strange-looking eyes. Two very different things can cause it, and telling them apart matters.
Cataracts are opacities in the lens that block light. They can be present from birth, develop after eye trauma or inflammation, or show up with age. A small cataract affecting 10 to 15 percent of the lens may not impair your cat’s vision at all. A mature cataract covering the entire lens causes significant vision loss, and you’ll usually see a distinctly white or milky area deep inside the eye.
Nuclear sclerosis, on the other hand, is a normal aging change. After about 8 to 10 years of age, the center of the lens gradually compresses and becomes denser, giving both eyes a faint bluish-gray haze. It looks concerning, but it doesn’t significantly affect vision. The two conditions can look similar to an untrained eye, but a vet can distinguish them by dilating the pupil and examining the lens closely.
A suddenly bluish or very cloudy eye is different from either of these. It can indicate a spike in eye pressure or severe inflammation, and it should be evaluated the same day.
A White or Pink Film Covering Part of the Eye
Cats have a third eyelid, a translucent membrane tucked in the inner corner of each eye. You might glimpse it briefly when your cat is falling asleep or just waking up. But if it’s visibly covering a portion of the eye during normal waking hours, something is off.
One well-documented cause is Haws syndrome, a condition seen mostly in young cats (typically under 3 years old). Both third eyelids protrude and the upper eyelids droop slightly, giving the cat an odd, sleepy appearance. Despite looking dramatic, the cats are generally healthy otherwise. About 40 percent of affected cats in one study also had diarrhea, and the condition appears to be triggered by a gastrointestinal infection that disrupts nerve signaling to the eyes. In most cases it resolves on its own within a few weeks, though it occasionally takes up to three months and can recur.
Third eyelid protrusion in just one eye is more concerning. It can signal pain in that eye, a foreign body behind the eyelid, or a nerve problem on that side of the face. If only one side is affected, or if your cat seems uncomfortable, get it checked out sooner rather than later.
New Dark Spots on the Iris
If your cat’s eye has developed brown or black spots on the colored part (the iris), you’re right to pay attention. These spots fall into two categories, and the distinction is important.
Benign iris melanosis consists of small clusters of pigment cells sitting flat on the iris surface. They tend to have sharp, well-defined borders and stay superficial. Freckles are the smaller version; nevi are somewhat larger patches. These can be present from birth or develop with age, and many cats accumulate more of them over the years. On their own, they’re harmless.
Diffuse iris melanoma is a slow-growing cancer that starts as pigmented patches but behaves differently over time. The spots tend to appear in multiple areas, gradually grow larger, and eventually merge together. The pigmented areas may look slightly raised with a velvety texture. As the tumor progresses, it invades deeper into the iris and can distort the shape of the pupil or affect how it responds to light. This type of melanoma is usually in one eye only.
If you notice new dark spots, the practical step is to photograph them in good light every few weeks. Spots that stay flat, small, and well-bordered are likely benign. Spots that spread, thicken, merge together, or change the shape of the pupil need veterinary evaluation. Many vets recommend monitoring iris spots with periodic photos and exams so any progression gets caught early.
Redness, Squinting, and Discharge
Conjunctivitis, or inflammation of the pink tissue lining the eyelids, is extremely common in cats. The telltale signs are squinting, frequent blinking, redness around the eye, and discharge. The type of discharge offers a clue about the cause: a clear, watery discharge often points to a viral infection or irritant, while thick, dark-colored, or yellowish discharge is more typical of bacterial involvement.
The most frequent infectious causes are feline herpesvirus and calicivirus, along with two types of bacteria. Herpesvirus is especially common and can flare up repeatedly throughout a cat’s life, often during periods of stress. Kittens and cats from shelters are particularly prone to their first bout. Mild cases sometimes improve on their own, but discharge that persists beyond a day or two, especially if it’s thick or colored, typically needs treatment to prevent corneal damage.
A Bulging or Enlarged Eye
Glaucoma causes pressure to build inside the eye, and it can make the eye look visibly larger or more prominent than normal. Normal eye pressure in adult cats sits around 20 mmHg. In cats with glaucoma, that pressure climbs significantly and continues rising if untreated. The eye may also appear cloudy, the pupil may be dilated and unresponsive to light, and your cat will likely show signs of pain like squinting or avoiding being touched on that side of the head.
Glaucoma in cats is less common than in dogs but tends to develop secondary to other eye diseases, particularly chronic inflammation. It progresses quickly and can cause irreversible damage to the optic nerve within hours to days. A bulging, cloudy, or suddenly enlarged eye is a same-day emergency.
What a Vet Eye Exam Involves
If you bring your cat in for a strange-looking eye, the exam is straightforward and non-invasive. A tear production test involves placing a small paper strip inside the lower eyelid for 60 seconds to measure moisture output. Tonometry uses a small handheld device tapped gently against the surface of the eye to estimate internal pressure, which helps diagnose both glaucoma (high pressure) and uveitis (low pressure).
For suspected corneal injuries, a fluorescein stain test is common. A drop of fluorescent dye is placed on the eye surface. Healthy corneal tissue repels the dye, but any area where the outer layer has been damaged absorbs it and glows green under a special light. This can reveal ulcers, scratches, and even tiny perforations. The same dye can also be used to check whether the tear drainage system is working properly by watching for the dye to appear at the nostrils.
None of these tests require sedation, and most cats tolerate them well. If the vet needs a closer look at the lens or the structures behind the iris, they’ll use a dilating eye drop, which takes about 15 to 20 minutes to work.
Signs That Need Same-Day Attention
Most eye changes in cats develop gradually and can wait for a regular appointment. But certain combinations signal an emergency: a suddenly blue or very cloudy eye, one pupil noticeably larger than the other with no recent change in lighting, eyes held tightly shut, visible pain (pawing at the face, hiding, refusing food), or any sudden loss of vision. These can indicate acute glaucoma, a deep corneal ulcer, or severe uveitis, all of which can cause permanent damage within hours if untreated.