Progressive retinal atrophy (PRA) is the umbrella name for a group of inherited disorders in which the light-sensing cells of the retina gradually break down. In cats the change is painless, slow and easy to miss. The first thing to go is usually vision in dim light, and many owners only realise something is wrong when their cat starts misjudging furniture in the evening.
What Is Actually Breaking Down
The retina contains two kinds of photoreceptors. Rods handle low-light vision, while cones handle colour and detail in bright light. In feline PRA the rods are usually affected first, which is why night blindness is the earliest clue. Over months to a couple of years the cones follow, and vision can be lost completely. Both eyes are affected, and the process cannot be reversed once those cells are gone.
PRA is inherited as a recessive trait, so a cat must receive the gene from both parents. Breeds with recognised risk include Abyssinian, Somali, Siamese, Balinese, Bengal, Persian, Ocicat, Cornish Rex, Oriental Shorthair, Munchkin, Peterbald and Singapura lines.
Signs Owners Notice First
- Hesitating or freezing when the room gets dim, or avoiding stairs at night
- Pupils that stay wide even in a bright room
- Bumping into furniture, especially in unfamiliar spaces
- Eyes that look more reflective or glassy than usual
- Clinginess, startle responses, or reluctance to jump
Because cats build a detailed mental map of their home, a gradual loss of sight can be compensated for months. Many cats are already in the later stages of the disease by the time it is diagnosed.
How Veterinarians Confirm It
A general eye exam in a cat with PRA typically shows sluggish pupillary light responses and a widened pupil. Fundus examination may reveal changes in the optic nerve head, narrowed retinal vessels and increased reflectivity of the tapetum lucidum, but early disease can look normal on a routine exam. The decisive test is electroretinography (ERG), which measures the retina’s electrical response to light and can detect PRA before obvious signs appear. DNA testing is available for some affected breeds.
Because slowly progressive blindness has other causes, your veterinarian will also rule out taurine deficiency, cataracts, glaucoma, uveitis, lens luxation and optic nerve disease. Most of those alternatives are painful and some are treatable, unlike PRA itself.
Treatment and Outlook
There is no treatment that restores or halts the loss of photoreceptors, and antioxidant or vitamin supplements have not been shown to change the course of the disease. If a cataract or a retinal detachment turns out to be the real problem, treating that condition may preserve vision. Cats diagnosed with PRA should not be bred.
The practical work is helping the cat live well. Keep furniture in place, keep food, water and the litter box in fixed and easy-to-reach spots, use textured rugs to mark key locations, and speak before you touch or pick your cat up.
When to Call Your Vet
Any sudden change in vision, a pupil that stays dilated, pain around the eye, or a cat that has started bumping into things should be seen promptly. Sudden blindness is an emergency, while gradual night blindness warrants a timely routine appointment. If you notice these changes, book an examination rather than waiting to see whether things improve.