Glaucoma in senior cats: symptoms, causes and treatment

Glaucoma in cats almost never announces itself. Where a dog with sudden glaucoma will often arrive at the clinic with an obviously red, squinting, painful eye, a cat tends to do something different — she becomes a touch quieter, hides a little more, stops jumping to the high shelf, and shows you an eye that looks only subtly off. A pupil that does not constrict quite right. An eye that looks marginally larger than its partner. A faint cloudiness across the surface. Nothing you would call an emergency on first glance. By the time most owners realize something is genuinely wrong, the disease has often been quietly at work for weeks or months.

That difference matters because it shapes how you should think about an aging cat's eye. Glaucoma is much less common in cats than in dogs, and when it does occur, it behaves differently. The vast majority of feline glaucoma is secondary — meaning something else inside the eye, or somewhere else in the body, set it in motion. A cat with glaucoma is rarely showing you a stand-alone eye problem; she is showing you a clue that points deeper. A thorough work-up is not optional, because the cause may be a treatable infection, a systemic disease, or a tumor that demands its own attention.

This guide walks through what glaucoma actually is, why secondary glaucoma dominates the feline picture, the diseases and conditions most often behind it, the subtle warning signs in senior cats, how veterinarians diagnose and treat it, when surgery is the kindest option, and how cats adapt remarkably well to life with reduced vision once the pain is gone. The goal is to help you notice trouble early, take it seriously when it looks small, and act on it before another eye is lost or another disease is missed.

What glaucoma actually is

The eye is not a hollow ball. It is a pressurized structure, kept firm and properly shaped by a clear fluid called aqueous humor that fills the front portion of the eye. The eye produces this fluid continuously, circulates it to nourish internal tissues, and drains it out through a filtering structure in the angle where the iris meets the cornea — the drainage angle. In a healthy eye, production and drainage stay in balance, and the pressure inside the eye stays within a comfortable range.

Glaucoma is what happens when that drainage system fails. Fluid keeps being made, but it can no longer escape at the proper rate, so it backs up. The pressure inside the eye — the intraocular pressure, or IOP — climbs above normal. That rising pressure does two devastating things. First, it hurts, the way a relentless pressure headache hurts, except trapped inside a small, delicate organ. Second, it crushes the structures that make vision possible — the retina and the optic nerve. Nerve fibers under sustained high pressure begin to die, and once they die, they do not come back.

In cats, the pressure rise tends to be slower and steadier than in dogs, which is why the disease is often described as chronic and insidious rather than acute. That does not make it any less serious. Slower does not mean safer — it means the damage piles up gradually while the cat hides what she feels, and by the time the eye looks dramatically different, the optic nerve may already be in trouble.

Primary vs. secondary glaucoma in cats

Veterinarians divide glaucoma into two broad categories, and in cats the distinction looks very different from dogs.

Primary glaucoma

Primary glaucoma is inherited — the drainage angle is structurally abnormal, with no other underlying eye disease driving the problem. In dogs, primary glaucoma is common and breed-related. In cats, primary glaucoma is rare. It does occur, occasionally in Siamese, Burmese, Persian, and a few other breeds, but it is not the typical story.

Secondary glaucoma

Secondary glaucoma develops because something else inside the eye is interfering with fluid drainage. In cats, this accounts for the overwhelming majority of cases — by some estimates more than ninety percent. The eye is paying the price for a different problem, and unless that underlying problem is identified and addressed, the glaucoma will be very difficult to control.

This is the single most important fact for owners to grasp about feline glaucoma: it is usually a symptom, not the disease itself. The implication is practical — your veterinarian will need to look hard not just at the eye but at the whole cat, including blood tests, infectious disease screening, and sometimes imaging. Treating the pressure without searching for the cause leaves the real problem free to keep doing damage.

What causes secondary glaucoma in senior cats

The causes of secondary glaucoma in older cats fall into a small number of recognizable patterns. Knowing them helps make sense of why the work-up after diagnosis is so thorough.

Chronic uveitis (inflammation inside the eye)

By far the most common cause of feline glaucoma is chronic uveitis — long-standing inflammation inside the eye. Inflammatory cells and debris physically clog the drainage angle, sometimes scar it shut, and pressure rises as a result. Uveitis itself is often a clue to systemic disease: feline leukemia virus (FeLV), feline immunodeficiency virus (FIV), feline infectious peritonitis (FIP), toxoplasmosis, bartonella, and certain fungal infections can all settle into the eye. In some cats no underlying cause is identified and the inflammation is called idiopathic — but that label is only applied after the systemic possibilities have been ruled out, not before.

Intraocular tumors

Tumors growing inside the eye are a serious cause of secondary glaucoma in senior cats. The most common is diffuse iris melanoma, which often begins as small dark spots on the iris and slowly spreads, eventually invading the drainage angle. Intraocular lymphoma is another important cause, especially in older cats. Because these tumors can also metastasize, an intraocular mass in an older cat is never just a local concern — it warrants careful evaluation and, in many cases, removal of the affected eye to both relieve glaucoma and reduce the risk of spread.

Lens luxation

The lens sits behind the iris, suspended by tiny fibers. When those fibers weaken — often after chronic uveitis or with age — the lens can slip forward or backward out of position. A lens that drops into the front chamber can physically block fluid drainage and cause a rapid, painful pressure spike. Lens luxation is less common in cats than in some dog breeds, but it does occur, particularly as a complication of long-standing inflammation.

Bleeding, trauma, and mature cataracts

Bleeding inside the eye, blunt or penetrating trauma, and advanced or hypermature cataracts (which can leak lens material and provoke severe inflammation) can all set the stage for secondary glaucoma in a senior cat. Trauma can be days, weeks, or even years in the past — old injuries sometimes catch up with the drainage angle long after the initial event.

Why senior cats are at higher risk

Glaucoma can strike at any age, but several things make older cats more vulnerable. The conditions that cause secondary glaucoma accumulate with age: chronic uveitis has had years to do its work, intraocular tumors become more likely, lens-supporting fibers weaken, and old eye injuries finally tip into trouble. Systemic diseases that drive uveitis — including FeLV, FIV, and certain chronic infections — also tend to surface in midlife and beyond.

There is also the quieter risk that has nothing to do with the eye itself. Cats are extraordinary at hiding discomfort, and senior cats often hide it inside the broader slowdown of aging. An owner may notice that an older cat sleeps more and jumps less and assume it is just one more sign of getting older. An eye that is gradually losing vision, or quietly hurting, can disappear inside that assumption. This is why subtle changes in a senior cat's eyes deserve a careful look rather than a shrug.

Warning signs of glaucoma in senior cats

The signs of glaucoma in cats are often easy to miss in the early stages. Watch for the following, especially if more than one appears together or if any of them develops on a single side.

A subtly enlarged eye

Because feline glaucoma is often chronic, the eye has time to stretch under sustained pressure. The result is buphthalmos — an eye that looks slightly larger than its partner. The asymmetry can be subtle; many owners only notice when looking at photos or by gently comparing the two eyes side by side. Any cat whose eyes do not match in size deserves veterinary evaluation.

A cloudy or hazy cornea

High pressure can cause the cornea — normally crystal clear — to take on a steamy, bluish-gray haze. This is different from the harmless gray of an aging lens deep inside the eye; corneal cloudiness sits at the very front and tends to develop over days to weeks. A foggy, ground-glass appearance to one eye is a red flag.

A dilated pupil that does not respond to light

A glaucomatous pupil is often dilated and may fail to constrict in bright light. A clear difference in pupil size between the two eyes, called anisocoria, is one of the most reliable early hints in cats. If you shine a soft light at your cat's eyes and one pupil stays large while the other narrows, that is worth a same-week conversation with your veterinarian.

Redness, squinting, and discharge

The white of the eye may look bloodshot, the cat may squint, blink excessively, or hold the eye partly closed, and there may be tearing or discharge. Because uveitis underlies so much feline glaucoma, signs of inflammation often accompany the pressure problem.

A visible third eyelid

The third eyelid — the pale membrane in the inner corner — may become more prominent in a painful eye. A third eyelid that suddenly stays partly across one eye, especially with other changes, warrants attention.

Behavior changes and signs of pain

Cats almost never cry or yelp from glaucoma pain. They withdraw. A cat with glaucoma may hide more, sleep more, eat less, stop grooming her face on one side, become irritable when touched near the head, miss her jumps, or simply seem off in a way you cannot quite name. Owners often only recognize how unwell their cat was in hindsight, after treatment, when she returns to herself.

Signs of vision loss

Bumping into furniture, hesitating on familiar paths, missing jumps she used to make easily, startling when touched, and reluctance to move in low light can all signal failing vision. Cats compensate so well — using whiskers, memory, and hearing — that one-eyed or even two-eyed vision loss can be remarkably hard to notice until it is advanced.

Why feline glaucoma still needs urgent care

Even though feline glaucoma tends to be slower and less explosive than the canine version, it is not something to manage at a leisurely pace. The optic nerve is still being damaged, the eye is still painful, and an underlying disease — sometimes a serious one — is often quietly progressing. Treat any suspected eye problem in a senior cat as a within-the-week veterinary issue at minimum, and a same-day call if the eye is suddenly red, bulging, painful, or the pupil is dramatically different from its partner.

There is also a smaller subset of cats whose glaucoma does behave acutely — particularly when a luxated lens or sudden bleed causes a fast pressure spike. In those cases the picture looks more like the canine emergency: a quickly red, painful, cloudy eye that needs hours-not-days care. When in doubt, call. A veterinarian would much rather see a cat whose eye turns out to be fine than miss the window on one whose eye is not.

How glaucoma is diagnosed

Diagnosis combines a direct measurement of eye pressure with a broader search for the cause.

Tonometry: measuring eye pressure

The cornerstone test is tonometry, performed with a small handheld instrument that gently touches the surface of the eye after a numbing drop. It is quick and well tolerated by most cats. A normal feline IOP runs roughly in the mid-teens to mid-twenties (millimeters of mercury); a glaucomatous eye reads notably higher. Tonometry confirms the diagnosis in seconds and gives a baseline for tracking treatment.

The full eye examination

Beyond pressure, the veterinarian will examine the whole eye — the cornea, the iris (looking carefully for pigment changes that could indicate melanoma), the position of the lens, the pupil's response, and, when possible, the retina and optic nerve at the back. Because secondary glaucoma is so dominant in cats, this exam is also a search for the underlying cause: signs of inflammation, a luxated lens, a mass, or bleeding.

The systemic work-up

This is where feline glaucoma diverges most clearly from canine glaucoma. A cat newly diagnosed with glaucoma usually needs blood work and infectious-disease testing — including FeLV and FIV screening, sometimes toxoplasmosis titers, and other tests guided by the cat's history and exam. Imaging, especially ocular ultrasound, may be used to look for an intraocular mass when the cornea is too cloudy to see through. The point of all this is not extra caution for its own sake; it is that the eye is often the messenger, and the message is worth reading.

Referral to a veterinary ophthalmologist

Many general-practice veterinarians will stabilize a glaucoma case and refer to a board-certified veterinary ophthalmologist for specialized evaluation and treatment planning. Specialists bring tools — gonioscopy of the drainage angle, advanced imaging, and a deeper familiarity with the surgical options — that can meaningfully change outcomes. If your cat is diagnosed with glaucoma, asking about referral is reasonable and often worthwhile.

Treatment options

Treatment of feline glaucoma has two intertwined goals: lower the pressure to relieve pain and preserve any remaining vision, and address the underlying disease that caused the glaucoma in the first place. Neither goal works well alone.

Treating the underlying cause

If chronic uveitis is the driver, anti-inflammatory therapy — often topical steroids or non-steroidal anti-inflammatory drops — becomes a central piece of treatment, along with any specific therapy aimed at an underlying infection. If a tumor is identified, removal of the eye (enucleation) is often the most appropriate option, both to control glaucoma and to address the cancer. If a luxated lens is to blame, the lens may need to be surgically managed. Pressure-lowering drops alone, without attention to the cause, rarely produce lasting control.

Pressure-lowering eye drops

Several classes of medications are used to lower IOP in cats, including topical carbonic anhydrase inhibitors (such as dorzolamide) and certain beta-blockers (such as timolol). One important species difference is that prostaglandin analogs like latanoprost, which work well in dogs, are generally less effective in cats and are sometimes avoided. Your veterinarian or ophthalmologist will choose drops appropriate for the feline eye and the underlying disease.

Successful medical management depends on consistency — drops given on schedule, every day, with rechecks to confirm pressures stay controlled. Missed doses allow pressure to drift back up. Many cats tolerate eye drops better than owners expect, especially when paired with calm handling and a small treat afterward.

Surgery to preserve vision

When an eye still has useful vision, ophthalmologists may offer procedures designed to lower pressure long-term — most commonly techniques that reduce fluid production within the eye, such as cyclophotocoagulation. These procedures can extend the working life of an eye, though none guarantees permanent success, and careful follow-up is essential. Vision-preserving surgery is most useful when caught relatively early, before the optic nerve has been badly damaged.

Surgery for a blind, painful eye

Many feline glaucoma eyes are already irreversibly blind by the time they are diagnosed, simply because the disease was so quiet for so long. A blind glaucomatous eye is not a harmless eye — it is still painful, and in cats it may also harbor a tumor that needs to be removed for the cat's overall health. For these eyes, the kindest path is enucleation, surgical removal of the eye, which ends the pain definitively and, when a tumor is present, also removes the disease.

Owners often grieve the idea of removing an eye, and that feeling is understandable. It helps to reframe it: the surgery does not take away a working eye — the eye is already blind, and in many cats it is also actively harming her. What it takes away is constant pain and, frequently, a tumor. Cats adapt to a single eye, or to total blindness, remarkably well, and most owners are struck by how much brighter their cat becomes once the painful eye is gone. In the small subset of cases where cosmetic appearance matters and the underlying cause allows it, an intraocular prosthesis may be discussed, but in cats — because tumors are so often the issue — full enucleation with biopsy is usually preferred.

Protecting the other eye

Because most feline glaucoma is secondary rather than inherited, the second eye is not automatically destined to develop the same disease. But it is not in the clear, either. The same underlying problem — chronic uveitis from a systemic infection, intraocular lymphoma, lens-supporting fibers weakening with age — can show up on the other side, sometimes months or years later. Cats diagnosed with glaucoma in one eye should have regular eye exams of the unaffected eye, including IOP measurement, and any new sign of inflammation or pupil asymmetry on that side should be acted on quickly.

For cats with a tumor-driven glaucoma, follow-up may also include monitoring for systemic spread of cancer. For cats with infection-driven uveitis, treatment of the underlying infection helps protect both eyes. Ask your veterinarian what specific monitoring plan is right for the cause your cat's glaucoma turned out to have.

Living with a blind or visually impaired cat

If glaucoma costs your cat her sight in one or both eyes, take heart: cats cope with blindness extraordinarily well. They rely heavily on whiskers, hearing, smell, and memory of their environment, and a blind cat who is no longer in pain can live a full, content, affectionate life.

A few thoughtful adjustments make the transition easier. Keep furniture in consistent places so your cat can map the home from memory. Block off stairs, balconies, and other hazards. Avoid carrying her to unfamiliar spots and setting her down — let her navigate from known starting points. Keep food, water, litter box, and a favorite bed in fixed locations. Talk to her as you approach so you do not startle her, and ask visitors to do the same. Add gentle audio cues — a soft chime on a collar can also help her find a multi-cat sibling. Most cats settle into a new, sightless routine within weeks and carry on being entirely themselves.

What to avoid

• Treating a feline eye change as too small to investigate. Slight pupil asymmetry, mild cloudiness, or one eye that looks just a little larger can be the first signs of glaucoma. They deserve an exam, not a watch-and-wait.
• Focusing on the eye and ignoring the rest of the cat. In cats, glaucoma is usually a symptom of something deeper. Skipping the systemic work-up means missing the real disease.
• Using leftover eye drops from another pet. Some medications safe for dogs are less effective or inappropriate for cats. Never medicate a cat's eye without veterinary guidance.
• Skipping doses of prescribed pressure-lowering drops. Glaucoma control depends on consistency; missed doses allow pressure — and damage — to creep back.
• Viewing eye removal as cruelty. A blind glaucomatous eye is a painful eye, and in cats it may also be a cancerous eye. Removing it ends suffering and, often, removes disease. Most cats feel dramatically better afterward.
• Assuming nothing can be done. Even when vision cannot be saved, pain almost always can be controlled, and the underlying disease often has its own treatment path.

When to See the Vet

Seek urgent veterinary care — same day if possible — if your senior cat has any of the following:

• A suddenly red or bloodshot eye
• A cloudy, hazy, or steamy-looking cornea
• An eye that looks enlarged, bulging, or different in size from its partner
• A pupil that stays dilated, or a clear difference in pupil size between the two eyes
• Squinting, excessive blinking, or holding an eye partly closed
• A third eyelid that suddenly stays partly across one eye
• Sudden bumping into objects, missed jumps, or other signs of vision loss
• Behavioral changes — hiding, irritability, withdrawal — paired with any visible eye change

Schedule a non-urgent but prompt exam if you notice subtle changes such as new dark spots on the iris, slowly developing pupil asymmetry, or gradual reluctance to navigate in dim light. And if your cat has already been diagnosed with glaucoma or chronic uveitis in one eye, any new change in the other eye should be treated as urgent.

Prognosis: what to expect

The honest picture varies more than in dogs because the cause matters so much. A cat whose glaucoma is driven by treatable uveitis from a controllable infection may keep useful vision for a long time if the underlying problem is addressed and pressure is well controlled. A cat with diffuse iris melanoma usually needs the eye removed and may need ongoing surveillance for spread, but enucleation often improves her quality of life dramatically. A cat with end-stage glaucoma in one eye and a still-comfortable second eye can live a perfectly happy life with a single eye for years.

What is consistent across causes is this: even when vision cannot be saved, the pain almost always can be. Whether through long-term medication, vision-sparing surgery, or removal of a blind painful eye, glaucoma in cats is a manageable condition in the sense that virtually every affected cat can be made comfortable again. Cats handle reduced vision with grace; what they cannot handle, and should not have to, is silent, untreated pain. Catching it, naming it, and acting on it is what changes the story.

Caring for a cat with glaucoma

A glaucoma diagnosis in a senior cat lands hard. There is worry about her vision, the demanding rhythm of daily drops, the difficult possibility of surgery, the unsettling discovery that the eye may be telling you about a deeper disease, and the quiet grief of watching an aging companion face one more hurdle. All of that is real, and you are allowed to feel it.

But it helps to hold on to what is within your control. You cannot undo the years that weakened the drainage angle or reverse nerve damage that has already happened. What you can do is be the person who notices the small things — the slightly different pupil, the eye that looks just a touch larger, the cat who stopped jumping to the bookshelf — and takes them seriously rather than waiting them out. You can keep the rechecks. You can give the drops, even on the days neither of you feels like it. You can be brave enough to choose the surgery that ends pain when it is the right choice. And if your cat's world dims, you can be the steady voice and the familiar hands that guide her through it.

Cats do not measure their lives in eyesight. They measure it in the warm spot in the sun, the sound of the can opener, the lap that appears in the evening, the voice that says her name from the doorway. A cat who has lost an eye to glaucoma — or even both — still has all of that, and with the pain gone, she has it without a shadow over it. Your job is simply to see the trouble clearly and quickly, get her the care she needs, look past the eye to whatever it might be pointing at, and then keep her world kind and predictable. Do that, and most cats go right on being exactly who they have always been.

This article provides general educational information about glaucoma in senior cats. It is not a substitute for individualized veterinary advice. Because feline glaucoma is usually secondary to another disease — chronic inflammation, intraocular tumors, lens displacement, or systemic infection — any changed, cloudy, asymmetric, or painful eye in a senior cat should be examined by a veterinarian, ideally a veterinary ophthalmologist, who can measure intraocular pressure, search for the underlying cause, and recommend the right treatment plan. If your cat develops a suddenly red, painful, bulging, or enlarged eye, or experiences sudden vision loss, contact your veterinarian or an emergency clinic the same day rather than waiting for a scheduled appointment.