Its parents and siblings should also be removed from breeding programs, even if they do not show any signs of the abnormality. Since the disease is heritable in these breeds, when a cat develops PRA, it should be removed from breeding programs. "Currently the only breeds in which this disease has been shown to occur as an inherited condition are the Abyssinian and Persian cats." In Persian cats, a recessive inheritance pattern has been confirmed but the specific gene has not been identified. In Abyssinian cats, retinal dysplasia has been recognized with a dominant inheritance, while late onset PRA appears to be inherited in an 'autosomal recessive' pattern, meaning that the affected cat must have inherited the defective gene from both parents. Are any breeds of cats more likely to get PRA?Ĭurrently the only breeds in which this disease has been shown to occur as an inherited condition are the Abyssinian and Persian cats. In the majority of cases, the rod cells degenerate first causing night vision to be affected before daytime vision, but eventually the cone cells also degenerate, leading to complete blindness. With late onset PRA, the cells of the retina develop normally, however over time, the cells begin to deteriorate. Usually, both the rods and the cones are affected. With retinal dysplasia, the photoreceptor cells of the retina develop abnormally, leading to an early onset of blindness. It is common for the late onset form to be called PRA and the early onset form to be called retinal dysplasia. There are two main forms of PRA recognized in cats, an early onset or inherited form, also called retinal dysplasia, which is typically diagnosed in kittens around two to three months of age, and a late onset form that is detected in adult cats, usually between the ages of two to five years. With this disease, the cells deteriorate over time, eventually leading to blindness in the affected cat. Progressive retinal atrophy (PRA), is a group of degenerative diseases that affect these photoreceptor cells. Cone cells do not work very well in low light.Ītrophy means the partial or complete wasting of a body part. Cone cells are responsible for detecting color. Rod cells are responsible for vision in low light conditions and for detecting and following movement. The cat's eyes contain many more rods than cones. The two main photoreceptor cells of the retina are the rod cells and the cone cells. When light enters the eyes, it is focused by the lens onto the retina, where it is converted into electrical signals that are sent to the brain for processing and interpretation. The retina is a light sensitive layer of cells at the back of the eye that contains cells called photoreceptors.
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