Progressive retinal Atrophy, cone-Rod dystrophy 3 (PRA-crd3) is an adult-onset inherited eye disease affecting Glen of Imaal Terriers. PRA-crd3 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 initially have changes in reflectivity and appearance of a structure behind the retina called the Tapetum that is typically observed on a veterinary eye exam at 3 years of age. Between 3 and 5 years of age affected dogs show signs of vision loss in dim light (night blindness) and loss of peripheral vision. Gradually visual deficits progress to complete vision loss over several years.