Uveitis in Cats: Signs, Causes, and Treatment

What uveitis is

The uvea is the middle layer of the eye. It includes the iris, which is the colored part, and the ciliary body behind it, which makes the fluid inside the eye. It also includes the choroid, a layer of blood vessels that nourishes the retina at the back of the eye.

Inflammation of the iris and ciliary body is called anterior uveitis. Inflammation at the back of the eye is posterior uveitis, and inflammation of the whole uvea is panuveitis. Uveitis can affect one eye or both. An injury or a tumor inside the eye usually affects only one eye. Illnesses that affect the whole body more often involve both eyes, although in cats they can also start in just one.

Signs to watch for

Some cats show clear pain. Others have mild changes that develop slowly and are easy to miss, especially when the problem has been going on for a while. Signs can include the following.

• Squinting, or keeping one eye half closed
• Watery or sticky discharge
• Sensitivity to bright light
• Redness in the white of the eye or the lining of the eyelids
• The third eyelid showing across the inner corner of the eye
• A cloudy or hazy look to the eye
• A small pupil, or pupils of different sizes
• A change in the color or texture of the iris
• Blood, or a pale layer of pus, settling at the bottom of the front of the eye
• Pawing at the eye, hiding, or avoiding being touched on the head

Some cats also have tiny pale spots on the inner surface of the cornea, the clear front of the eye. These are clumps of inflammatory cells. If your cat also has weight loss, a poor appetite or low energy, a full checkup is a good idea, because the eye may be showing a wider illness.

Common causes

In many cats, no cause is found even after testing. Vets call this idiopathic uveitis, and the immune system is thought to play a role. A UK study looked at 92 cats seen at referral clinics for uveitis that was not caused by an injury. Just under half of the cases were idiopathic. When a cause is found, it is often one of these.

• Feline infectious peritonitis (FIP), the most common known cause in that UK study
• Feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV)
• Toxoplasmosis, an infection with a single-celled parasite
• Cancer, especially lymphoma
• High blood pressure, often linked to kidney disease or an overactive thyroid in older cats
• An injury to the eye, such as a scratch or a bite from a fight

Age can give a clue. In the UK study, cats with FIP tended to be young, while cats with cancer tended to be older. Less often, fungal or bacterial infections, diabetes, irritating chemicals in the eye, or protein leaking from a damaged lens are involved.

Several of these causes are serious and treatable, so vets usually look for an underlying disease before settling on idiopathic uveitis. FIP is a good example. It was once almost always fatal. Antiviral treatment now helps most cats with FIP recover, although it is not available in every country. An early diagnosis gives a cat the best chance.

When it is an emergency

It is best to have a vet check a painful eye as soon as possible, ideally the same day. Uveitis can damage the eye quickly. It can also look like other urgent problems, such as a corneal ulcer or glaucoma, which is high pressure inside the eye.

Contact a vet urgently if your cat suddenly seems blind, bumps into things, or has wide pupils that stay large in bright light. The same applies to blood inside the eye, an eye that looks enlarged or very cloudy, or strong pain with the eye held shut. In older cats, sudden blindness with dilated pupils can be a sign that high blood pressure has caused the retina to detach. Prompt treatment gives the best chance of keeping vision.

How vets diagnose it

Diagnosis starts with a close look at the eye using a bright light and magnification. The vet will often apply a dye to check the cornea for scratches or ulcers, and measure the pressure inside the eye. Pressure is usually low with uveitis and high with glaucoma, so this test helps tell the two apart and guides treatment.

Next comes the search for a cause. This often includes a physical exam, blood and urine tests, tests for FIV and FeLV, tests for toxoplasmosis and other infections, and a blood pressure reading. X-rays or an ultrasound can look for disease in the chest and belly. Some cats are referred to a veterinary eye specialist, who may examine the back of the eye in detail or test a small sample of fluid from inside the eye.

Testing takes time and can be costly, and even complete testing does not always find a cause. Your vet can help you decide which tests make the most sense for your cat.

How it is treated

Treatment has two aims. The first is to calm the inflammation and relieve pain. The second is to find and treat any underlying cause.

Anti-inflammatory eye drops or ointments are the usual starting point. Steroid drops are common, but vets use them only after a dye test shows the cornea is not ulcerated. Drops that widen the pupil can ease pain from spasm inside the eye and help stop the iris from sticking to the lens. Some cats also need anti-inflammatory medicine by mouth. Vets choose the type with care, because steroids given by mouth can make some infections worse.

When a cause is found, it is treated as well. That might mean an antibiotic for toxoplasmosis, antiviral treatment for FIP, blood pressure medicine, or cancer treatment. Cats with idiopathic uveitis may need drops for months, and some need long-term treatment to keep flare-ups under control.

Regular rechecks let the vet measure eye pressure again and adjust the plan. Ask your vet before stopping any medicine, even if the eye looks better.

Outlook

With prompt treatment, many cats start to improve within a day or two, although cloudiness or blood in the eye can take longer to clear. The outlook depends on the cause and on how quickly treatment starts. Severe or repeated inflammation can lead to glaucoma, cataracts, a displaced lens, a detached retina, or scarring where the iris sticks to nearby tissue. These can cause lasting blindness. If an eye becomes permanently blind and stays painful, your vet may suggest removing it to end the pain.

Risk to other pets and people

Uveitis itself is not contagious. Some of its causes can spread, and the risk depends on the cause.

FIV spreads mainly through deep bite wounds between cats. FeLV spreads through close contact, such as mutual grooming, bites, and shared food bowls or litter boxes. There is no evidence that either virus causes illness in people or dogs.

The parasite that causes toxoplasmosis can infect people. Most people catch it from undercooked meat, and a review of studies found that contact with cats was not a risk factor. A cat usually sheds the parasite in its feces only once in its life, for a short time after it is first infected. The shed eggs need at least a day in the litter to become infectious, so cleaning the litter box daily and washing your hands afterward lowers the risk further. Pregnant women and people with a weak immune system are usually advised to avoid handling cat litter. Ask your doctor for advice.

Prevention

There is no known way to prevent idiopathic uveitis. The risk from many known causes can be reduced. Keeping cats indoors or in a secure outdoor space cuts down on fights, bite wounds and hunting. This lowers exposure to FIV, FeLV and toxoplasmosis. FeLV vaccination is recommended for kittens and for cats that may meet other cats outdoors, so ask your vet whether it suits your cat. Feeding cooked or commercial food instead of raw meat lowers the chance of toxoplasmosis. For older cats, vets often recommend regular checkups that include a blood pressure reading.

Rescued and newly adopted cats

Rescued cats often have unknown histories. Life on the street can mean fights, eye injuries, hunting and contact with sick cats. At Paw Squadron, the first stops after every rescue are the vet and a bath, with a checkup, deworming and treatment against fleas and other parasites. Every animal gets a checkup, treatment, vaccinations and a microchip before adoption.

Eye changes can still appear later. Plan a visit to your own vet soon after adoption and bring the records you received. Ask whether FIV and FeLV tests have been done, since testing is recommended before a new cat meets the other cats in your home.

If you notice a red, cloudy or squinting eye, book a vet visit promptly. You can find more cat health guides in PawPedia, and cats looking for homes on our Adoptions page.