Moderate severity
Progressive Retinal Atrophy (PRA)
An inherited degeneration of the retina that slowly steals sight, starting with night vision. Painless, untreatable — and remarkably well tolerated.
⚠️ Common symptoms
Owners rarely bring a cat in because it has gone blind. They bring it in because it has started refusing to jump onto the bed at night, or because someone noticed that its eyes have been oddly wide and lamp-like in photographs recently. PRA is slow, symmetrical and painless, and cats compensate for it so thoroughly that a substantial proportion of vision can be gone before anyone suspects anything.
The pattern of loss follows the biology. Rods, the photoreceptors responsible for vision in low light, degenerate first, so the first real-world consequence is a cat that is fine in daylight and lost at night. Cones follow, and daylight vision fades over months to years. Meanwhile the retina thins and the reflective tapetum behind it becomes more exposed, which is why the eyeshine of an affected cat grows unusually bright — a subtle sign, but one that shows up clearly in flash photographs and that has tipped off more than a few owners.
Because the eye is not painful and does not look diseased, the examination is what settles it. Through an ophthalmoscope the tapetal reflectivity is increased, the retinal blood vessels are thinned and attenuated, and in advanced cases the optic disc is pale. An electroretinogram, which measures the electrical response of the retina to light, is more sensitive still and can identify affected cats years before any visible change, which is chiefly useful in breeding programmes.
What makes the diagnosis worth pursuing, given that nothing can be done, is everything it excludes. Sudden blindness with widely dilated pupils in an older cat is far more likely to be hypertensive retinopathy, where the retina has detached because of uncontrolled blood pressure — that is an emergency, sometimes reversible, and frequently the first sign of hyperthyroidism, kidney disease or an adrenal tumour. Taurine deficiency produces a characteristic central retinal lesion and is reversible if the diet is corrected. Neither should be mistaken for an untreatable inherited disease.
The consolation is genuine. Cats manage blindness better than almost any other companion animal, navigating by whisker, memory, scent and hearing, and a cat that loses sight gradually has years to build the mental map it will rely on. Keep the furniture where it is, keep the cat indoors, and most affected cats carry on with a normal life that surprises visitors who cannot tell anything is wrong.
🔍 Causes
PRA in cats is inherited, and two forms are well characterised. An early-onset recessive form seen in Abyssinians and Somalis, caused by a mutation in the CEP290 gene, affects kittens within the first months of life. A later-onset form, associated with the CRX gene, occurs in Abyssinians and Somalis too and progresses more slowly in adulthood. Persians have their own early-onset recessive form. The disease is also reported sporadically in Bengals, Siamese and domestic shorthairs. In all forms the photoreceptors of the retina — rods first, then cones — degenerate progressively, which is why night vision fails long before daylight vision does. Importantly, PRA must be distinguished from the acquired retinal degeneration caused by taurine deficiency, which looks similar but is nutritional and preventable.
🛡 Prevention
The disease cannot be prevented in an affected cat, but it can be bred out. DNA tests exist for the Abyssinian and Somali mutations and for the Persian form, and responsible breeders test their stock and avoid mating two carriers, which is how affected kittens arise. Anyone buying a pedigree kitten from an at-risk breed is entitled to ask to see the parents' test results. Separately, the taurine-related retinal degeneration that mimics PRA is entirely preventable by feeding a complete commercial cat food — it appears in cats fed dog food or unsupplemented home-prepared diets, and remains a real risk for owners cooking for their cats without veterinary formulation.
💊 Treatment
There is no treatment that halts or reverses the degeneration. Antioxidant supplements are sometimes suggested but no product has been shown to change the course of the disease in cats, and owners should be wary of anything marketed as a cure. What genuinely helps is environmental management, and cats do extremely well with it: keep furniture, litter trays, food and water in fixed positions, avoid rearranging rooms, block off stairs and balconies if the cat is unsteady, and use scent and texture cues — a different mat by the litter tray, for instance — to help with navigation. Talk to the cat as you approach so it is not startled. Confirming the diagnosis still matters even though nothing can be done about it, because it rules out the causes of vision loss that are treatable and urgent, particularly hypertensive retinal detachment and taurine deficiency.
⚕️ Medical disclaimer
- This information is educational only and is not a substitute for veterinary advice.
- Symptoms overlap between conditions — only a vet can diagnose accurately.
- Never withhold treatment or self-medicate based on information found online.
- When in doubt, call your vet. Early intervention almost always leads to better outcomes.