PRA, Progressive Cone-Rod Degeneration (PRA-prcd)
Progressive retinal atrophy, progressive rod-cone degeneration (PRA-prcd) is a late onset, inherited eye disease affecting many breeds of dog. PRA-prcd occurs as a result of degeneration of both rod and cone type photoreceptor cells of the retina, which are important for vision in dim and bright light, respectively. Evidence of retinal disease in affected dogs can first be seen on an electroretinogram around 1.5 years of age for most breeds, but most affected dogs will not show signs of vision loss until 3 to 5 years of age or later. The rod type cells are affected first and affected dogs will initially have vision deficits in dim light (night blindness) and loss of peripheral vision. Over time affected dogs continue to lose night vision and begin to show visual deficits in bright light. Other signs of progressive retinal atrophy involve changes in reflectivity and appearance of a structure behind the retina called the tapetum that can be observed on a veterinary eye exam. Although there is individual and breed variation in the age of onset and the rate of disease progression, the disease eventually progresses to complete blindness in most dogs. Other inherited disorders of the eye can appear similar to PRA-prcd. Genetic testing may help clarify if a dog is affected with PRA-prcd or another inherited condition of the eye.
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