Progressive retinal atrophy (PRA) in cats: when blindness is preventable with a DNA test

In 30 seconds

Progressive retinal atrophy (PRA) is a group of inherited diseases that gradually destroy the retina's photoreceptor cells (rods and cones), producing slow vision loss that ends in total blindness. There is no cure, and the progression is one-directional. The reason PRA matters more than most hereditary feline diseases is that it is one of the few that is completely preventable: a DNA test has existed since 2007 for the most common form, and a responsible breeder who tests both parents will never produce an affected kitten. Most affected cats start losing night vision between 1.5 and 2 years of age and go fully blind between 3 and 5. The breeds at highest risk are the Abyssinian, the Somali, the Ocicat, and the Bengal.

Genetically distinct forms of feline PRA

PRA is not a single disease. Several genetically separate forms have been identified, each tied to particular breeds and each caused by a different mutation. They look similar in the exam room but trace back to different genes.

rdAc-PRA

The most studied form, caused by a mutation in the CEP290 gene. It was first characterized in the Abyssinian, which is why the older literature ties it so closely to that breed. It has since been documented in:

• Abyssinian, where the mutation was first identified.
• Somali, essentially a semi-longhaired Abyssinian and the same gene pool.
• Ocicat, which carries Abyssinian ancestry in its foundation.
• Siamese and Oriental lines, at lower frequency.

The clinical course is gradual night blindness from around 1.5 to 2 years, progressing to complete blindness between 3 and 5 years.

Rdy / early-onset PRA

A separate mutation in the CRX gene produces a much earlier and faster form, sometimes called Rdy. Affected kittens show retinal abnormalities within the first weeks of life and lose vision far sooner than rdAc cats. This dominant form has been described in Abyssinian and related lines.

PRA in other breeds

The Bengal has its own recognized form, and additional variants have been documented in the Persian and other breeds. Not every variant has a validated commercial DNA test yet, so a clear ophthalmic exam in these breeds does not carry the same certainty that a clean rdAc genotype does in an Abyssinian.

Clinical signs (and why owners miss them)

Early PRA is genuinely hard to spot, because cats compensate so well with smell, hearing, and spatial memory inside a familiar home. A cat that has gone substantially blind in its own apartment can navigate normally until the furniture moves. Watch for:

1. Reluctance to move in low light. The cat hesitates to leave a dim room or freezes at the edge of an unlit hallway.
2. Bumping into objects in unfamiliar spaces. A new house, a hotel carrier, or rearranged furniture exposes the deficit that a fixed home hides.
3. Persistently dilated pupils. The eyes stay wide even in bright light, a compensation for reduced light reaching the retina.
4. A more intense green "eye shine" in flash photos. This reflects changes in the tapetum and retina and is sometimes the first thing an owner notices in pictures.
5. Behavioral changes. More vocalization, and more seeking of human contact for orientation.

Diagnosis

Genetic test

The rdAc DNA test has been available since 2007 through the UC Davis Veterinary Genetics Laboratory, with other labs offering it as well. A cheek swab returns one of three results:

• Clear (normal): no copies of the mutation.
• Carrier (heterozygous): one copy. The cat will not go blind from rdAc but passes the mutation to roughly half its offspring.
• Affected (homozygous): two copies. The cat will develop rdAc-PRA.

Cost runs about $50 to $120 per test in the US. Reputable Abyssinian, Somali, and Ocicat breeders have tested as a matter of course since the test became available.

Ophthalmic examination

A fundus (retinal) exam by a board-certified veterinary ophthalmologist (an ACVO Diplomate) detects visible retinal changes: vascular attenuation, tapetal hyperreflectivity, and optic disc pallor in advanced cases. This is the confirmatory imaging step and the one that catches variants without a DNA test.

Electroretinography (ERG) measures the electrical response of the retina to light. It can detect functional loss before the changes are visible on the fundus, which makes it useful in early or pre-clinical cases.

Living with a cat that has PRA

There is no curative treatment. PRA progresses to total blindness regardless of intervention. The reassuring part is that a blind cat lives an almost normal life with sensible management, because cats lean on smell, hearing, and memory far more than on sight to begin with:

• Keep the furniture where it is. A blind cat memorizes the layout, and moving the couch is what actually trips it up.
• Block the hazards. No open balconies, no unguarded stairwells, no access to high ledges it can fall from.
• Use sound and scent to your advantage. Speak as you approach so you do not startle the cat, and keep the environment predictable.
• Fix the locations of the food bowl and litter box. Once set, do not move them.
• Offer cognitive enrichment with scented or sound-based toys rather than light-up or laser toys.
• No free outdoor roaming. A catio or a supervised harness walk gives safe enrichment without the risks of traffic and fights.

PRA itself does not shorten lifespan. The added risk comes from the blindness, mainly trauma from falls, vehicles, or conflicts with other animals, which is exactly what indoor management removes.

Prevention

This is the part that separates PRA from most hereditary diseases: rdAc is fully preventable through DNA testing in the at-risk breeds. The breeding protocol that eliminates affected kittens is straightforward:

1. Buy from a breeder with documented PRA tests on both parents. Ask to see the results, not just a verbal assurance.
2. Never breed two carriers together. That cross gives each kitten a 25 percent chance of being affected.
3. Clear by carrier is acceptable. That cross produces no affected kittens; about half will be carriers, which are then tested and bred only to clear cats. This keeps useful genetics in the pool without producing blind animals.

For breeds with a faster or earlier form such as Rdy in some Abyssinian lines, a clear ophthalmic exam in the foundation cats adds a layer of confidence where a single DNA test does not cover every variant.

Common questions

My cat is from one of the at-risk breeds. Should I test even if it shows no symptoms?

If you are breeding, yes, always: a carrier looks completely normal and is exactly how the mutation spreads silently. If your cat is a neutered pet and you simply want to know whether it will go blind, the rdAc test answers that for the most common form, though a clear result does not rule out the rarer variants that lack a commercial test.

Can the blindness be reversed if caught early?

No. PRA destroys photoreceptors, and there is no approved treatment in cats that restores or halts retinal degeneration. Early detection helps you prepare the home and rule out treatable causes of vision loss, not reverse the disease.

My cat suddenly seems blind. Is that PRA?

Probably not on its own. PRA is gradual over months to years. Sudden blindness in a cat points instead to hypertension with retinal detachment, which is common in older cats with kidney disease or hyperthyroidism and is sometimes treatable if caught fast. Sudden vision loss is an urgent vet visit, not a wait-and-see.

Is a blind cat in pain?

PRA is not painful. The retina degenerates without inflammation or pressure changes. A blind cat that bumps into a moved object is disoriented, not hurting. If the eye itself is red, cloudy, or squinting, that is a different problem and warrants an exam.

How do I find a veterinary ophthalmologist?

The American College of Veterinary Ophthalmologists maintains a directory of board-certified ACVO Diplomates, with representation in most US metropolitan areas. Your general-practice vet can refer you for the fundus exam, ERG, and the breeding-relevant eye certification.