Disorders of the Anterior Uvea in Cats - Cat Owners - Merck Veterinary Manual (2024)

The uvea (or the uveal tract) is the colored inside lining of the eye consisting of the iris, the ciliary body, and the choroid. The iris is the colored ring around the black pupil. The ciliary body is the set of muscles that contract and relax to allow the lens to focus on objects; it is also the source of aqueous humor, the clear fluid in the eye. The choroid is the inner lining of the eyeball. It extends from the ciliary muscles to the optic nerve at the back of the eye. The choroid also contains layers of blood vessels that nourish the inside parts of the eye, especially the retina. The anterior uvea refers to the uvea in the front of the eye: the iris, the ciliary body, and the anterior chamber angle; however, diseases that affect the anterior uvea often affect the choroid as well.

Persistent Membranes Across the Pupil

Persistent membranes across the pupil are the remains of the normal prenatal blood vessels that fill the region of the pupil. The persistence of colored strands across the pupil from one area of the iris to another, or to the lens or cornea, is seen occasionally in cats.

Atrophy of the Iris

A weakening and shrinking in size (atrophy) of the iris can be seen in cats. It can involve the edge or the connective tissue of the pupil. Shrinkage of the edge of the pupil creates a scalloped border and a weakening of the sphincter muscle, which results in a dilated pupil or slowed reflexes of the pupil in response to light. Shrinkage of the connective tissue results in dramatic holes in the iris, and often, displacement of the pupil. Neither of these types of atrophy appears to affect vision. Animals lacking a functional sphincter muscle (which controls the opening and closing of the iris) may show increased sensitivity to bright light.

Cysts of the Iris

Cysts of the iris are usually colored spheres in the liquid part within the eye. In cats, they are frequently attached at the edge of the pupil. Therapy is rarely necessary because they do not interfere with vision, but removal or rupture of a cyst may occasionally be required.

Inflammation of the Anterior Uvea

Inflammation of the front portion of the uvea (the iris and the ciliary body) is called anterior uveitis or iridocycl*tis. It occurs frequently in cats. It may be seen in one eye (as a result of trauma, eye parasites, or various types of cancers) or in both eyes (as a result of a whole-body infection or immune-mediated diseases). The effects of anterior uveitis may be destructive to the eye and can affect vision.

Common infectious diseases that can cause anterior uveitis include feline infectious peritonitis and feline leukemia (both viral infections), feline immunodeficiency virus infection, toxoplasmosis (a disease caused by microscopic parasites), generalized fungal infection, and leptospirosis (a bacterial infection). Often, anterior uveitis is the only sign of these disorders, so it is very important to have your cat examined by a veterinarian if it shows signs such as squinting of the eyelids, a protruding third eyelid (nictitating membrane), abnormally red or bloodshot eyes, or any other changes to the eye.

Your veterinarian will want a thorough medical history of your pet to help in diagnosing this condition. Other diagnostic steps may include examination of the cornea for injuries, a physical examination, blood tests, and tests on fluid from your pet’s eye. Reducing the eye inflammation requires treating the underlying primary disease with appropriate drugs. Cortico-steroids are sometimes prescribed to treat cloudiness, reduce the inflammation, and reduce the chance of developing glaucoma. Antibiotics are necessary if there is a bacterial infection.

Hyphema (Bleeding Within the Eyeball)

Bleeding inside the eyeball is called hyphema. It may appear as liquid or clotted blood. Causes include uveitis, traumatic injury, a tumor within the eye, detachment or tearing of the retina, high blood pressure, clotting disorders, birth defects, and glaucoma. Sudden, severe bleeding usually has a good outcome if the cause is identified and treated. Recurrent or longterm hyphema has an unknown or poor outlook because glaucoma or blindness is likely. Although no drugs are available to treat hyphema, certain medications may help.

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Disorders of the Anterior Uvea in Cats - Cat Owners - Merck Veterinary Manual (2024)


What causes anterior uveitis in cats? ›

The infectious causes most commonly associated with feline uveitis include feline leukemia virus, feline immunodeficiency virus, feline infectious peritonitis, systemic fungal infections, toxoplasmosis, and bartonellosis. Neoplastic causes of uveitis can be primary or secondary.

What is the uvea of a cat's eye? ›

The uvea is the part of the eye made up of the iris (the thin, circular structure that gives the eye its color and controls the size of the pupil), the ciliary body (part of the wall of the eye that makes the fluid that fills the eye) and the choroid (middle layer of the eye).

What is a cat's eyelid disease? ›

The most common congenital eyelid abnormality that can predispose a cat to developing blepharitis is entropion, a condition in which the edges of the eyelid turn inwards and rub against the cornea.

Is uveitis in cats contagious to humans? ›

Uveitis does not pose a risk to humans, but certain infectious causes of uveitis may be contagious to humans (zoonotic). These can include bartonellosis, toxoplasmosis and others. Talk with your healthcare provider if your pet is diagnosed with a zoonotic condition.

What is the most common cause of anterior uveitis? ›

Viral. Viral infections are the most common infectious underlying etiology of anterior uveitis. Increased IOP, iris atrophy, and unilateral presentations are common with viral etiologies.

What is the most common symptoms of anterior uveitis? ›

  • Eye redness.
  • Eye pain.
  • Light sensitivity.
  • Blurred vision.
  • Dark, floating spots in your field of vision (floaters).
  • Decreased vision.

How do you treat anterior uveitis in cats? ›

Corticosteroids may be administered by injection under the lid of the eye, by drops in the eye, or as an oral medication, depending on the suspected cause of uveitis. Topical use must be postponed if damage to the corneal surface is present because the corticosteroids prevent healing of the ulcer.

What are the symptoms of anterior uveitis in cats? ›

Often, anterior uveitis is the only sign of these disorders, so it is very important to have your cat examined by a veterinarian if it shows signs such as squinting of the eyelids, a protruding third eyelid (nictitating membrane), abnormally red or bloodshot eyes, or any other changes to the eye.

Is uveitis in cats fatal? ›

Uveitis is more prevalent in the dry form. FIP breaks down the blood-ocular barrier, causing uveitis and fibrin leakage into the eye's front chamber. FIP signs include fever, lethargy, decreased appetite, incoordination, and seizures. Once a cat shows FIP signs, the disease is almost always fatal.

What is Horner's syndrome in cats? ›

Horner's syndrome is a common neurological disorder of the eye and facial muscles, caused by dysfunction of the sympathetic nervous system. The condition usually occurs suddenly and typically affects one side of the head but can be bilateral (affect both sides of the head) in rare cases.

What does Haws syndrome look like in cats? ›

Haw's syndrome is when a cat's third eyelids become visible across both eyes, with no other eye abnormalities. The third eyelid (also called the nictitating membrane) is a thin white piece of tissue. You might spot them if your cat is very sleepy, or occasionally when they blink.

What does blepharitis look like in cats? ›

Symptoms of Blepharitis in Cats

Redness, scabbing, or crusting of the eyelids. Rubbing or pawing at the affected eye(s) Sores or wounds around the eyes. Watery or thick, clear to green discharge from the eyes.

How do you diagnose anterior uveitis? ›

Diagnosis. The symptoms of anterior uveitis can be similar to those of other eye conditions. Therefore, a doctor of optometry will carefully examine the front and inside of the eye with a unique microscope using high magnification.

Can allergies cause uveitis in cats? ›

This is the first known report of a primarily eosinophilic uveitis in a cat with chronic allergic skin disease and may be considered an ocular variant of feline eosinophilic granuloma complex.

Is anterior uveitis contagious? ›

Anterior uveitis is not an infection and it is not contagious. The symptoms of Anterior uveitis include light sensitivity, throbbing eye pain, and blurred vision. The eye will look very red and inflamed and some patients need to wear sunglasses to help with the light sensitivity.

Does uveitis in cats go away? ›

Many cases of feline uveitis are resolved via a veterinary visit for a thorough examination, diagnostic testing, and medication therapy. Your cat will have a follow-up visit for the vet to assess healing and resolution of the condition. Other cats are less fortunate and will require months of treatment.

Can cat scratch disease cause uveitis? ›

Conclusions: We firstly reported a case of Cat-scratch disease presenting simultaneously with uveitis and fundus nodular lesions caused by Bartonella henselae infection in a child. Timely diagnosis and treatment with antibiotics and corticosteroids showed promising outcomes for the prognosis of these ocular disorders.

Does anterior uveitis go away? ›

Sometimes uveitis goes away quickly, but it can come back. And sometimes it's a chronic (long-term) condition. It can affect 1 eye or both eyes. Uveitis can cause vision loss if it isn't treated — so it's important to see your eye doctor right away if you have symptoms.

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