Progressive retinal Atrophy, X-linked 1 (XLPRA1) is an inherited eye disease affecting dogs. XLPRA1 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 by a year of age, but visual deficits may not be evident until dogs are at least 2 years of age. 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. As the disease progresses, cone photoreceptor cells also degenerate resulting in complete blindness. 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. Due to its X-Linked Inheritance, male dogs are more frequently affected with this disease than female dogs. Other inherited disorders of the eye can appear similar to XLPRA. Genetic testing may help clarify if a dog is affected with XLPRA or another inherited condition of the eye.