Uveitis

This patient had some bleeding inside the eye, as is evident by the reddish haze in the front of the eye.

“Uveitis” is the term used to describe general inflammation inside the eye. Any number of symptoms may be seen with this condition, but typically the whites of the eyes are red and the pet is squinting, indicating that the eye is painful. The pupil may be more constricted than usual and the eye may appear to be cloudy. Redness inside the eye could indicate bleeding inside the eye. Sometimes the iris will change in color. Often these signs are indicative of a potentially serious disease elsewhere in the body, so it is important to get your pet to a veterinarian right away if any of these symptoms are seen.

How is uveitis diagnosed?

The diagnosis of uveitis is based on your pet’s history, symptoms, and a thorough ocular exam. A hallmark sign of uveitis is the presence of aqueous flare, which can be seen by shining a very small, bright beam of light through the eye. If the beam appears cloudy, much like how a beam of light shone through a dusty movie theater would be cloudy, then aqueous flare is present. The flare is caused by inflammatory proteins within the eye that are not present in a healthy eye.

A hallmark sign of uveitis is the presence of aqueous flare, which can be seen as cloudiness when a very small, bright beam of light is shone through the eye.

What causes uveitis?

Uveitis is often caused by another disease in the body. In general, the causes can be categorized into four large groups: infectious, cancerous, traumatic, and immune-mediated. Since the range of causes is so broad, a thorough work-up, including laboratory work, chest x-rays, and abdominal ultrasound, is typically recommended so that a diagnosis may be made and appropriate treatment started. Unfortunately, despite these tests, the cause is never determined in up to 75% of uveitis cases. When this happens, the patient is treated symptomatically.

Infectious Causes

Infectious causes of uveitis vary by species. Tick-borne diseases, including Lyme disease, Ehrlichia, and Rocky Mountain spotted fever, are reported causes of uveitis in dogs1,2. In cats, toxoplasmosis, feline immunodeficiency virus (FIV), feline leukemia, and Bartonellosis are reported causes3,4. Both species should have a urinalysis performed to rule out a urinary tract infection that may have spread to the eye. Fungal infections are less common in the Washington D.C. area, but testing for these may be recommended as well.

Cancerous Causes

Cancerous causes includes lymphosarcoma, tumors of the eye, ocular melanosis, and metastasis (spreading) of other cancers. Metastatic cancers can sometimes be detected on x-rays if they have spread to the lungs. Abdominal ultrasound is helpful in detecting more obvious tumors and enlarged lymph nodes, which may indicate lymphosarcoma. If a tumor of the eye is suspected, an ocular ultrasound or CT scan may be recommended. If a tumor or cancer is diagnosed, your pet may be referred to a veterinary oncologist for treatment options.

Traumatic Causes

Traumatic causes of uveitis include blunt trauma to the head and penetrating trauma to the eye. Blunt traumas can cause the retina to detach, leading to bleeding and inflammation inside the eye. Penetrating traumas can lead to lens-induced uveitis if the lens is damaged (see Immune-Mediated Causes) and severe infection if bacteria get trapped inside the eye.

Uveodermatologic syndrome in a Jack Russell terrier that resulted in depigmentation of the nose.

Immune-Mediated Causes

Immune-mediated diseases cause the body to react to its own tissues as though they were foreign substances. Veterinary ophthalmologists suspect that most cases in which a cause cannot be definitively determined are actually immune-mediated. Two specific immune-mediated diseases are uveodermatologic syndrome and lens-induced uveitis. In uveodermatologic syndrome, the body attacks pigment cells, including the pigment inside the eye. These patients will often show depigmentation of the eyelids and nose in addition to the ocular symptoms. Lens-induced uveitis occurs in patients with advanced cataracts when the lens protein leaks into other parts of the eye. The eye sees the lens protein as foreign material and begins to attack it, which results in uveitis. It can also occur in an eye without cataracts when a trauma such as a cat scratch penetrates the lens and damages it, releasing lens proteins into the eye.

Treatment of Uveitis

Uveitis must be treated aggressively in order to prevent permanent damage to the eye. Treating the underlying cause is the most effective way to treat the uveitis if the cause can be determined. Regardless of the cause, treatment of the eye includes anti-inflammatory medications to minimize the inflammation inside the eye and usually a pain medication. Uveitis is often recurrent in pets even with proper treatment.

References:

1.Massa, Kathleen L., Brian C. Gilger, Tammy L. Miller, and Michael G. Davidson. “Causes of uveitis in dogs: 102 cases (1989–2000).” Veterinary Ophthalmology 5.2 (2002):93-98.
2.Munger, RJ. “Uveitis as a manifestation of Borrelia burgdorferi infection in dogs.” Journal of the American Veterinary Medical Association 197.7 (1990):811.
3.Powell, Cynthia C., and Michael R. Lappin. “Diagnosis and Treatment of Feline Uveitis.” Compendium 23.3 (2001):258-269.
4.Ketring, Kerry L., Evelyn E. Zuckerman, and William D. Hardy, Jr. “Bartonella: A New Etiological Agent of Feline Ocular Disease.” Journal of the American Animal Hospital Association 40 (2004):6-12.

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