Progressive retinal Atrophy (Irish setter type) is an early onset, inherited eye disease affecting dogs. Progressive retinal atrophy (Irish setter type) 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. The rod type cells are affected first and dogs present around 1 month of age with vision deficits in dim light (night blindness) and loss of peripheral vision. By 5 months of age dogs have complete loss of night vision and also 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 variation in disease progression, generally the disease follows a rapid progression and dogs are typically completely blind by 1 year of age.