Serious severity
Glaucoma
A painful rise in the pressure inside the eye that damages the optic nerve. It can destroy vision quickly, so a sudden case is treated as an emergency.
⚠️ Common symptoms
Glaucoma is, at its heart, a plumbing problem with devastating consequences. The eye constantly produces a clear fluid that nourishes its internal structures and is meant to drain away at the same rate it is made. When that drainage fails, fluid backs up, the pressure inside the eye climbs, and that pressure squeezes the two structures vision depends on most — the retina and the optic nerve. Sustained high pressure damages them irreversibly, which is why glaucoma is one of the leading causes of preventable blindness in cats, and why a sudden case is treated as an emergency.
What sets cats apart from dogs is the cause. In dogs, inherited glaucoma from a faulty drainage angle is common. In cats it is rare; instead, feline glaucoma is almost always secondary — a complication of some other disease within the eye. By far the most important of these is uveitis, long-standing inflammation inside the eye that gums up the drainage pathways. That inflammation is frequently a downstream sign of a bigger problem, including the viral infections FeLV, FIV and FIP, or the parasite toxoplasmosis. Lens problems, internal bleeding and tumours round out the list.
The signs can be dramatic or deceptively subtle. A classically affected eye looks cloudy or bluish, red and bloodshot, and may bulge noticeably as the globe stretches under pressure; the pupil is often dilated and unresponsive. But cats are masters at concealing discomfort, and many simply become quiet and withdrawn, squint, or start misjudging jumps and bumping into things as their sight fades. Because the condition is painful — chronic glaucoma has been likened to a constant severe headache — even a stoic cat is suffering.
Management aims first to drop the pressure fast with medicated drops and tablets, buying time and easing pain, and then to tackle the underlying cause so the problem does not simply return. Sadly, by the time many cats are presented the affected eye is already blind, and when such an eye remains painful the most humane and effective course is to remove it. Owners are often distressed by that prospect, but cats cope extraordinarily well with one eye and are visibly more comfortable afterwards. The enduring lesson is that eye problems in cats move fast: a red, cloudy or painful eye is never something to watch and wait on.
🔍 Causes
Glaucoma occurs when fluid (aqueous humour) cannot drain from the eye as fast as it is produced, so pressure builds and presses on the delicate retina and optic nerve. In cats, unlike dogs, the great majority of cases are secondary — caused by another eye problem rather than an inherited drainage defect. The most common culprit is chronic inflammation inside the eye (uveitis), which can itself stem from infections such as FeLV, FIV, FIP or toxoplasmosis. Other causes include a displaced lens, bleeding inside the eye, and tumours within the eye. Primary (inherited) glaucoma, common in some dog breeds, is rare in cats.
🛡 Prevention
Because most feline glaucoma is secondary to another disease, prevention means catching and treating those underlying problems early — particularly uveitis, which is the leading trigger. Any cat with a red, squinting or persistently watery eye should be examined promptly rather than left to settle, and cats diagnosed with viral infections such as FeLV or FIV benefit from periodic eye checks. Keeping vaccinations and parasite control up to date reduces the infectious causes of the inflammation that so often precedes glaucoma.
💊 Treatment
Treatment has two goals: lower the eye pressure quickly to relieve pain and salvage any remaining sight, and find and treat whatever is causing it. Medications — eye drops and sometimes oral drugs — are used to reduce the production of fluid within the eye and improve its drainage. Because feline glaucoma is usually secondary to another disease (such as inflammation, a lens problem or a tumour), managing that primary condition is central to controlling the pressure. When an eye is already blind and persistently painful, the kindest option is often surgical removal of the eye (enucleation), which reliably ends the pain; cats adapt remarkably well to life with one eye. Lifelong monitoring is the rule, as the other eye may later be affected.
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⚕️ Medical disclaimer
- This information is educational only and is not a substitute for veterinary advice.
- Symptoms overlap between conditions — only a vet can diagnose accurately.
- Never withhold treatment or self-medicate based on information found online.
- When in doubt, call your vet. Early intervention almost always leads to better outcomes.