Progressive retinal Atrophy, Rod-cone dysplasia 2 is an early-onset, inherited eye disease affecting smooth collies. Progressive retinal atrophy, rod-cone dysplasia 2 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. Affected dogs have abnormal thinning and degeneration of the retina beginning around 16 days 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 noticeable at about 6 weeks of age. 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 at 3.5-4 months of age on a veterinary eye exam. As the disease progresses, cone photoreceptor cells also degenerate resulting in complete blindness by 6 to 8 months of age.