Glaucoma in Cats: The Silent Eye Disease That Can Cause Blindness Fast

Glaucoma has a reputation as a dog and human eye disease, and it's genuinely less common in cats. That reputation gap causes real problems, though, because when glaucoma does show up in a cat, it tends to hide behind vague, easy-to-miss signs right up until vision is already at serious risk.

What glaucoma actually is

Glaucoma is a buildup of pressure inside the eye, caused by fluid (aqueous humor) draining out more slowly than it's produced. According to the Merck Veterinary Manual, that rising pressure damages the retina and optic nerve over time, and if it isn't brought down, the damage becomes permanent. Normal eye pressure in a cat sits roughly in the 15 to 25 mmHg range, and pressure meaningfully above that is what a vet is checking for with a quick, painless instrument called a tonometer.

Why it's almost always "secondary" in cats

Unlike dogs, where primary glaucoma (an inherited drainage problem with no other underlying cause) is relatively common, VCA Animal Hospitals notes that the large majority of feline glaucoma cases are secondary, meaning something else is driving it. Uveitis, inflammation inside the eye, often from an underlying viral, immune, or inflammatory condition, is the most common culprit, since the resulting debris and scar tissue can physically block the eye's normal drainage angle. This matters practically: treating feline glaucoma effectively usually means identifying and addressing whatever's causing the underlying uveitis, not just lowering the pressure number in isolation.

Why cats hide it so well

Cats are notoriously good at masking pain and discomfort, and glaucoma is no exception. Rather than obvious squinting or crying out, an affected cat more often shows subtle changes: a bit more withdrawn, slightly reduced appetite, or bumping into furniture as vision quietly declines. Physical signs to watch for include a cloudy or bluish-tinted cornea, one eye appearing larger than the other (buphthalmos, from the eyeball itself stretching under pressure), and dilated pupils that don't react normally to light. PetMD notes that by the time these signs are obvious enough for an owner to notice unprompted, meaningful vision loss has often already occurred, which is exactly why regular vet checkups matter more here than waiting for clear symptoms.

Why this counts as a genuine emergency

Acute glaucoma is painful and fast-moving. The Merck Veterinary Manual's emergency medicine guidance notes that vision can be lost within hours to days once pressure spikes significantly, and emergency treatment (sometimes an intravenous medication to rapidly pull fluid out of the eye, alongside pressure-lowering eye drops) is aimed at buying back time for the eye before permanent damage sets in. A cat with a sudden change in eye appearance, especially paired with obvious discomfort, needs same-day veterinary attention rather than a wait-and-see approach.

Ongoing management

Long-term treatment usually combines pressure-lowering eye drops with treating whatever underlying uveitis or inflammation is driving the problem. In eyes where vision is already lost and pain can't be controlled, removing the eye is sometimes the treatment that actually gives the best quality of life, which understandably sounds drastic but reliably resolves the chronic pain a blind, high-pressure eye otherwise causes.

Frequently asked questions

Is glaucoma in cats always caused by another eye problem?
Not always, primary glaucoma can rarely occur in cats, but secondary glaucoma driven by uveitis or another underlying issue is by far the more common pattern.

Can glaucoma affect just one eye?
Yes, and it often does, at least at first, which is part of why comparing both eyes side by side (size, clarity, pupil response) is a useful thing for owners to check periodically.

Is a cat with one blind eye from glaucoma still a good candidate for adoption or a normal life?
Generally yes. Cats adapt remarkably well to vision loss in one or even both eyes, especially in a stable, familiar indoor environment, and typically go on to live full, comfortable lives once the underlying pain is addressed.

Sources

• Merck Veterinary Manual, "Glaucoma in Cats"
• Merck Veterinary Manual, "Acute Glaucoma in Small Animals"
• VCA Animal Hospitals, "Glaucoma in Cats"
• PetMD, "Glaucoma in Cats"

This article is for general information and isn't a substitute for advice from your own veterinarian. A cat with a sudden change in eye appearance or apparent eye pain needs prompt veterinary attention.