Section: Information In-depth
A diagnosis of anterior uveitis simply means there is inflammation inside the eye. Numerous diseases can manifest as uveitis, so it can be difficult to diagnose the underlying cause. Some of the diseases mentioned below may be confined to the eye. However, in other cases, the condition may affect multiple parts of the body and the eye is but one aspect of disease. A pet may have either predominately ocular signs (those pertaining to the eye) or multisystemic signs such as weakness, lethargy, decreased appetite, coughing, fever or other problems.
Infectious causes of anterior uveitis are numerous. Some common causes include:
Viral diseases. FIV (feline immunodeficiency virus), FeLV (feline leukemia virus), FIP (feline infectious peritonitis virus).
Protozoal disease. Toxoplasmosis is a protozoan parasite that is more common in the cat than the dog . It is potentially a zoonotic disease, meaning that people can acquire this disease from cats that are shedding the parasite in bowel movements. If your cat is diagnosed with toxoplasmosis, it is essential to ask your veterinarian and physician about the risk. This is especially important for pregnant women, young children, elderly or immune-compromised individuals.
Fungal diseases like blastomycosis, histoplasmosis, cryptococcosis, coccidiodomycosis, candidiasis. Different fungi are more common in dogs versus cats and in certain regions of the world. Cryptococcosis and histoplasmosis occur more often in the cat. Fungal diseases often involve the posterior (back) segment of the eye as well as the front.
Many different strains of bacteria and different types of toxins. Sometimes a remote infection such as a uterine or kidney infection may lead to inflammation inside the eye. Many tick borne diseases cause uveitis in the dog, but rarely do so in the cat.
Other causes of anterior uveitis include:
Tumors can cause anterior uveitis. The appearance varies, but the clinical signs of inflammation (uveitis) are common.
Lymphoma – The iris is generally thickened and there may be focal yellowish, white or pink discoloration.
Melanoma – The iris is generally thickened and darker brown than usual.
Adenoma or adenocarcinoma – Often appears as a pink white mass peaking through the pupil from behind the iris.
Trauma. Any type of injury to the head or eye can cause a uveitis because the uvea contains numerous blood vessels, so secondary inflammation and "bruising" can occur.
Metabolic diseases. Because the uvea is an extension of the body's circulating blood system, many diseases that affect the body can have an impact on the eye. Examples include hypertension, elevated circulating proteins, and uremia.
Lens-induced anterior uveitis may develop when cataracts are present. A cataract is an opacity of the lens. Lens-induced uveitis is more common in the dog, but may occur in the cat if some sort of penetrating trauma to the eye disrupts the lens.
Immune-mediated diseases. In these diseases, the animal's immune system "attacks" itself. These diseases tend to occur primarily in the dog, and include such conditions as thrombocytopenia, in which platelets are being attacked and destroyed, and hemolytic anemia, in which red blood cells are being attacked and destroyed by the immune system. Any uveitis associated with these conditions is a secondary effect.
Secondary diseases complicating anterior uveitis may include glaucoma, cataract formation, blindness, and lens luxation.
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