In inflammation or infection, both barriers may collapse and permit the passage of larger molecules, inflammatory cells and blood cells into the eye. The intraocular structures are normally separated from the choroidal and retinal blood vessels by two barriers the blood-aqueous barrier and the blood-retinal barrier. Prompt diagnosis of underlying viral infection in cats with ophthalmic disease is paramount for accurate diagnosis and prognosis and is required for appropriate therapeutic decision-making. Feline herpes virus is probably also a cause of uveitis. The most important causal agents are corona virus (feline infectious peritonitis), retrovirus (feline leukemia virus, feline immunodeficiency virus), Toxoplasma gondii, and various mycoses. In recent reports, between 38% and 70% of the cats with uveitis have concurrent systemic disease. Uveitis with or without chorioretinitis is one of the most frequent and significant ophthalmic diseases in cats. Books & VINcyclopedia of Diseases (Formerly Associate).VINcyclopedia of Diseases (Formerly Associate).Tracy Dewhirst is a freelance contributor to the News Sentinel. It is important to know if the mydriasis is due to feline leukemia or a more serious problem that could be causing pain or leading to irreversible blindness. I recommend you have your cat's eyes examined, especially if he has another episode of mydriasis. Some cases of spastic pupil syndrome are self-limiting, meaning the pupil can return to a normal size, but others may remain fixed. This retrovirus causes many abnormal signs in cats, including what is sometimes referred to as "spastic pupil syndrome". If your cat truly has mydriasis and was positive for Feline Leukemia virus, the mydriasis is most likely caused by the virus. Iris atrophy is another possibility as animals age the muscles and fibers of the pupil can degenerate, leaving the pupil unable to constrict, resulting in mydriasis. And, unique to cats, each side of the pupil is controlled by a separate nerve therefore, only one side of the pupil may be involved. Some topical and systemic drugs also can affect nerve function causing pupil dilation, but systemic drugs will dilate both eyes. Glaucoma must also be ruled out because mydriasis occurs when the increase pressure interrupts the normal movement of the pupil or damages the retina, causing blindness. Retinal or optic nerve damage can cause loss of vision leading to mydriasis because the sensory system that detects light is not working. It is important to know if the animal has displayed any loss of vision, especially night vision, or has experienced any trauma. This is important since the pupil size is dictated by many different factors including muscles, nerves, sensory input and eye pressure. We also use a bright source of direct light to test the function of the pupil under intense light the pupil should constrict appropriately.Īnimals with unequal pupils should have an ophthalmic exam done by a veterinarian.
We do this by placing the animal in a darkened room if the eye with the smaller pupil size dilates normally then the mydriatic eye is the problem. Conversely, when the pupil cannot dilate properly and remains constricted this is referred to as miosis.Īnytime an animal presents with pupils of unequal size, we must determine if one pupil is abnormally dilated or if, in fact, one is abnormally constricted. I would like your opinion.Ī: When the pupil of the eye is unable to constrict normally, or fixed and dilated, this condition is called mydriasis. Other than the eyes, he is a well-behaved, frisky cat. This might go on for several days, but then the eye will return to normal. Sometimes the pupil of one eye will be dilated while the other one is normal. He has been with us for more than 3 years and seems healthy, but there is one problem that is baffling. We took him to the vet and were told he had Feline Leukemia.
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