Progressive retinal atrophy, PRA1 (papillon type) occurs as a result of degeneration of the Rod type Photoreceptor Cells of the Retina, which are important for vision in low light.

Affected dogs typically present between 4 to 6 years of age with poor vision in dim light.

On a veterinary eye exam affected dogs have changes in reflectivity and appearance of a structure behind the retina called the Tapetum as well as thinning of the retinal blood vessels, signifying decreased blood flow to the retina.

Progressive retinal atrophy, PRA1 (papillon type) is slowly progressive and some affected dogs maintain vision in daylight for many years, sometimes for the remainder of their life.