inflammation of the uveal tract, which is the pigmented, vascular part of the eye
What is it?
Uveitis is inflammation of the uveal tract, which is the pigmented, vascular part of the eye. This includes the iris (this is the colored part of the eye that forms the pupil), ciliary body, and choroids. The uveal tract (or “uvea”) is all in one piece, and is shaped like a hollow ball with a large slit in it, that fits inside the eyeball. The slit is the cat’s pupil, and the rest of the ball is the iris, ciliary body, and choroid which all “blend” together as a vascular cup. Therefore, if the iris is inflamed, it is likely that the ciliary body and choroid are involved too, either slightly or severely.
What are the symptoms?
Uveitis can have many clinical signs. Common clinical signs, that can be mixed and matched in a variety of combinations, are as follows: squinting, sensitivity to light, third eyelid protrusion, tearing, redness to the white part of the eye, abnormal pupil shape or size, an altered iris color (usually a “muddy” or reddened color compared to the normal color), cloudiness, cataract, and/or enlarged eye if glaucoma is present. Blindness may be apparent, but this is often not noticeable, especially if the fellow eye is visual.
How is it diagnosed?
In approximately 6 out of every 10 cats with uveitis, the cause cannot be identified, even with extensive diagnostic tests. However, when the cause can be identified, it is usually trauma, an infectious disease, or cancer. The infectious diseases that can cause uveitis in cats are: Toxoplasma gondii, feline infectious peritonitis (FIP), Bartonella henselae, feline immunodeficiency virus (FIV), feline herpesvirus-1 (FHV-1) and feline leukemia virus (FeLV). The two most common types of cancer that can cause uveitis in cats are lymphoma and also diffuse iris melanoma (DIM). It is important to know that all of these diseases can be life threatening, with perhaps the exception of feline herpes virus.
How is it treated?
The treatment for uveitis depends on the cause. Anti-inflammatory medication is usually prescribed for topical use and sometimes oral use. It is important to determine if glaucoma is present as a complication of uveitis, as this needs to be treated. Most veterinarian general practitioners do not have an instrument (called a tonometer) to measure the intraocular pressure. If the elevated intraocular pressure is not controlled, the eye will become blind and painful. The pain is a “headache” type of discomfort that is NOT obvious to the owner.
What is the prognosis?
It is important to understand that even with the best treatment care of the cat, the uveitis might not be controlled and glaucoma can occur. Also, it is important to know that uveitis in cats is usually a lifetime disease that requires lifetime treatment.