Uveitis is when part of the eye (the uvea) becomes inflamed. The uvea is a layer of tissue inside the eye that includes the iris (the colored tissue visible surrounding the pupil that controls the size of the pupil), the ciliary body (hidden behind the iris), and the choroid (hidden at the back of the eye).

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• Anterior uveitis means the iris and the ciliary body are inflamed.
• Posterior uveitis means the choroid is inflamed, and because the retina (the part of the eye that senses light) lies on top of the choroid, the retina is often also inflamed with posterior uveitis, so the term "chorioretinitis" is used to describe this.
• Panuveitis is when all the parts of the uvea (iris, ciliary body, and choroid) are inflamed.

The signs of uveitis depend on what parts of the uvea are inflamed, how bad the uveitis is and how long it has been going on. With anterior uveitis and panuveitis, the symptoms can be obvious and include:

• A red eye.
• Squinting.
• Tears.
• Light sensitivity/avoiding bright light.
• Cloudiness.
• A change in the color or shape or size of the pupil.
• Vision loss.

• Glaucoma (high pressure in the eye).
• Cataracts (a clouding of the lens).
• Anterior lens luxation (when the lens becomes loose and moves from its usual position in the eye.

Uveitis is a reaction that can happen because of a problem that only affects the eye (like cataracts, a corneal ulcer/scratch, a tumor in the eye, trauma to the eye) but it can also develop as a reaction to disease that affects the body (infections, toxins, blood disorders, cancer, immune-mediated diseases).

Uveitis is diagnosed by performing a full eye exam, including measuring the pressure in the eye. Sometimes this needs to be performed by a specialist ophthalmologist to find the uveitis, as specialist skills and equipment are needed since other eye diseases can look like uveitis and much of the uvea is hidden inside the eye. Once uveitis is found during an eye exam, then it is important to find out why your cat has uveitis, since there are so many different causes. Sometimes, the cause is easily found during the eye exam (such as a cataract). If the cause of the uveitis isn't obvious, then it's important that your cat is tested for diseases of the body that could be the trigger for the uveitis. This testing can include:

• A thorough history to ask about any other changes in your cat's behavior or travel.
• A thorough physical exam.
• General bloodwork (complete blood count, serum biochemistry).
• Urine testing (urinalysis).
• X-rays of the chest and abdomen, and an ultrasound scan of the abdomen.
• Infectious disease tests (usually bloodwork or urine testing for viruses, bacteria, parasites, fungi) - the specific tests recommended for infectious disease depend on where your cat lives or has traveled.

Uveitis can be painful. The worse the uveitis is, the more likely it is to be painful. Some cats show obvious signs of pain/eye irritation such as squinting, tearing, and light sensitivity. Some cats may not show obvious signs of eye irritation but could still have some discomfort as the pain is thought to be more "headache-like". One complication that is common from uveitis is secondary glaucoma, where the pressure in the eye can become high, which can be uncomfortable.

Uveitis can be treated, usually with anti-inflammatory eye drops and/or pills. The aim is to control the uveitis as quickly as possible. Other medications may also be prescribed, to treat the underlying trigger of the uveitis, such as antibiotics for a bacterial infection. It is important that uveitis is diagnosed quickly, before too much damage has occurred in the eye from the inflammation, otherwise there is a risk of blindness and pain. The longer the uveitis has been going on the more risk of damage to the eye. Some types of uveitis go away when the trigger is cured (such as if the uveitis was caused by a scratch to the cornea or an infection in the body that can be treated) but other causes of uveitis can need lifelong treatment (such as if there is a cataract in the eye or some immune-mediated diseases. Each case is individual, and the proper treatment will be decided by your veterinarian. Careful monitoring with regular rechecks is important if your cat has uveitis, as this can be a very serious disease and your cat needs to be watched closely for any signs of complications like glaucoma and to adjust the medications they are taking for uveitis. The outcome of your cat's uveitis depends on how bad it is, what the underlying cause is, how much damage the uveitis caused, if complications like secondary glaucoma or cataracts have developed, and how they respond to the treatment. Early diagnosis and aggressive treatment to control the disease as quickly as possible has the best outcomes. Occasionally, the damage to the eye is too great from the uveitis and the eye is irreversibly blind and painful (glaucoma has usually developed at this stage) - in this situation, surgery to remove the eye can be performed and this will resolve the pain. Cats adapt extremely well to vision loss.

See the Vetlexicon Felis factsheet Eye drops - how to administer them.