Uveitis In Cats - Seattle Animal Eye Clinic

ANIMAL EYE CLINIC INFORMATION SERIES!
Anatomy of the eye
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Uveitis in Cats
The Uvea
The word “uveitis” means inflammation inside
the eye. The uvea is the middle layer of the eye. It
includes the iris, the ciliary body, and the
choroid. Inflammation of these structures can
result from many causes, and can result in damage to
structures inside the eye, potentially leading to
vision loss and discomfort.
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ANIMAL EYE CLINIC INFORMATION SERIES!
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WHAT IS UVEITIS?
Uveitis is inflammation of the inner middle layer of
the eye. Inflammation can result from many causes,
and basically means swelling, redness, oozing. Just
as a finger will swell, turn red, and become painful if
struck by a hammer or becomes infected, the uvea
can swell, become red, and leak protein, fluid, or
white blood cells when inflamed.
WHAT ARE THE CAUSES OF UVEITIS IN CATS?
Uveitis can result from trauma (blunt or penetrating), various types of infection within the
eye, certain types of cancer, or due to autoimmunity.
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Trauma: Just as a finger
swells and turns red when struck
by a hammer, the layers of the eye
will swell & become inflamed when
subjected to trauma. This can be a
blunt injury, or some type of penetrating injury. Typically the inflammation subsides on its own
over time, but permanent damage
to the eye can result.
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Infection: Inflammation is one way the body fights infection. It allows the body to send
antibodies, white blood cells, and
other disease-fighting molecules to
the site of infection. Uveitis can result from infections inside the eye (bacterial, viral, fungal, protozoal), or on the surface of the eye (cornea).
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Cancer: Various types of cancer can result in uveitis. Solitary tumors inside an eye
will cause inflammation as they grow within the normal tissues. These can be primary tumors- i.e. started in the eye, or metastatic tumors- i.e. spread to the eye from some other
place in the body. Cancer elsewhere in the body can also cause the immune system to attack the eye inappropriately- so called paraneoplastic uveitis.
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Autoimmunity: This is by far the most common type of uveitis in cats. In this
situation the body’s immune system has become sensitized to uveal tissue- it regards these
normal intraocular structures as a dangerous foreign invader and attacks the uvea as if it
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were a bacteria or virus. The cause of this sudden change is unknown. This is similar to
other autoimmune conditions like Lupus, Rheumatoid arthritis, etc...
Based upon the specific historical and ophthalmic findings in your pet, your doctor may
suggest various tests to help elucidate the specific type of uveitis.
WHAT HAPPENS WHEN THE UVEA IS INFLAMED?
In most cases active uveitis is uncomfortable, although cats will act far more “normal” than
dogs. The eyes might become bloodshot, you may see increased light-sensitivity, cloudiness,
and vision can be affected by increased murkiness of the intraocular fluids. Unfortunately
the most common type of uveitis in
cats in our area is something called
pars planitis. The pars plana is part
of the ciliary body- a narrow strip of
tissue behind the pupil. Chronic inflammation in this location is often
inapparent from the exterior- the
eyes will look normal to an owner until damage is considerable. Inflammation can lead to permanent damage to structures within the eye as
well. Damage to the lens can lead to
cataract formation and the ligaments
that anchor the lens in position behind the iris can break down allowing the lens to shift
position (lens luxation). Damage to the drain inside the eye can lead to increasing pressure as fluid is unable to exit normally (glaucoma). Fluid can leak from the back wall of
the eye separating the retina from the wall (retinal detachment). Every time the inflammation is active, additional damage is done, so keeping uveitis controlled is very important
if vision and comfort are to be maintained.
HOW IS UVEITIS TREATED?
When a specific cause is discovered, treatment includes specific therapy directed at that
cause. Fungal infection would be treated with antifungal medications, bacterial infection
with antibiotics. In addition to these specific therapies we would employ antiinflammatory
medications. These might include corticosteroids like prednisone and dexamethasone
(drops and/or tablets depending on severity and part of the eye involved) and nonsteroidal
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ANIMAL EYE CLINIC INFORMATION SERIES!
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antiinflammatory medications (NSAIDs). Sometimes we will treat with drops to dilate the
pupil- in certain types of uveitis much of the associated discomfort results from spasm of
the muscles that constrict it. Dilation in those cases therefore improves comfort. In cases
where the cause is autoimmunity, medications might also include immunosuppressive
therapies- typically higher doses of steroids given orally to reduce the drive behind the immune system’s attack. Autoimmune uveitis usually requires lifelong treatment to maintain
control, although medications are usually decreased over time to reduce potential side effects. Your ophthalmologist will discuss the treatment options based upon your pet’s individual situation.
WILL MY PET LOSE VISION COMPLETELY?
This is possible- even with all available treatment. Your doctor will discuss the prognosis
for your pet based upon the stage of disease and treatments selected. It is important to
keep in mind that most blind cats have an excellent quality of life as long as comfort is
maintained. Not only are they in a protected and loving environment, cats use vision very
differently than humans with their other senses far more developed than ours. Sudden vision loss will take a longer period of adjustment than a gradual decline, but in either case
most owners report that their pets adapt remarkably well.
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