What is progressive retinal atrophy (PRA)?

• A. Inherited autosomal recessive form of retinal degeneration with progressive irreversible loss of rods THEN cones
• B. Inflammation of the retina
• C. Glaucoma
• D. Cataracts

Answer: (A)

Progressive retinal atrophy is a hereditary retinal dystrophy where the photoreceptor cells gradually degenerate, starting with the rods (which control night vision) and eventually affecting the cones, leading to a progressive, irreversible loss of vision. It is commonly inherited as an autosomal recessive condition in many dog breeds (and is analogous to retinitis pigmentosa in people). Early signs are night blindness and poor navigation in low light, followed by diminishing daylight vision and central acuity as cones are lost. On eye examination, you may later see peripheral pigment changes and vascular attenuation as the disease progresses, though early stages can appear normal. This pattern and progression distinguish PRA from inflammatory retinal disease, glaucoma, or cataracts, which involve different mechanisms and timelines. The defining feature is the gradual, irreversible loss of photoreceptors beginning with rods and advancing to cones.