The retina is a thin, delicate membrane that lines the back of the eye and is actually an extension of the optic nerve. In a healthy cat, the retina receives light, processes it, and passes it on to the brain. If the cells are damaged, it can’t send anything on. In a cat with retinal disease, the retinal cells are damaged and the eye is no longer able to properly transmit information regarding the light it receives. The visual image may be blurred, and part or all of the visual field may be blacked out.
Retinal diseases usually begin with the loss of night vision. When this happens, the cat hesitates to go out at night or won’t jump onto or off furniture in a darkened room.
Progressive Retinal Atrophy
Progressive retinal atrophy is the degeneration of the retinal cells over time. In cats, retinal diseases usually are not caused by genetic influences, although a hereditary form of progressive retinal atrophy occurs in Persians, Abyssinians, and possibly Siamese. The mode of inheritance appears to be autosomal recessive.
Treatment: Progressive retinal atrophy has no treatment and eventually leads to blindness. It is hoped that a genetic screening test will be available in the future so breeders can avoid this problem.
Retinitis is a disease in which inflammation of the retina leads to degeneration and destruction of the light receptors. It occurs in association with toxoplasmosis, feline infectious peritonitis, lymphoma, cryptococcosis, and systemic fungus infections. It may also occur as a consequence of hypertension, or eye injury, or for unknown reasons. In these cases, the retina may actually become detached from the back of the eye. High blood pressure or hypertension is one of the most common causes of this condition. The hypertension is usually associated with hyperthyroidism and/or renal failure. Immediate medical treatment may stop the progression of this detachment.
Treatment: The outlook for useful vision depends on the cause and extent of retinal damage at the time of diagnosis. Medical diseases, such as hypertension, are treatable. Control or cure can prevent further damage. If caught early, retinal detachments caused by trauma may sometimes be repaired - or at least, further damage can be prevented. This requires referral to a veterinary specialist.