Progressive retinal Atrophy, cone-Rod dystrophy 2 is an early-onset, inherited eye disease affecting American pit bull terriers. The disease affects the Photoreceptor Cells of the Retina and results in the progressive loss of vision. Affected dogs typically have abnormal thinning and degeneration of the retina by 12 weeks of age. Evidence of retinal thinning can be identified on a veterinary eye exam by 3 to 6 months of age. Vision is severely impaired by one year of age and by 20 months of age, affected dogs have an advanced stage of retinal degeneration.