Progressive retinal Atrophy, golden retriever 1 (GR-PRA1) is a late-onset inherited eye disease affecting Lhasa Apsos. Affected dogs begin showing clinical symptoms related to retinal degeneration between 6 to 7 years of age on average, though age of onset can vary. Initial clinical 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. Progression of the disease leads to thinning of the retinal blood vessels, signifying decreased blood flow to the retina. Affected dogs initially have vision loss in dim light (night blindness) and loss of peripheral vision, eventually progressing to complete blindness in most affected dogs.