The retina is a light-sensitive cell layer at the back of the eye that contains photoreceptors. The lens focuses light that enters the eye onto the retina, and the photoreceptors convert the information into electrical signals that are sent to the brain for processing and interpretation. The retinal photoreceptors are classified as rod cells and cone cells. Rod cells are responsible for detecting and following movement and for low light vision, while cone cells detect color and don’t work well in low light situations. Cats have more rods than cones in their eyes.
Progressive retinal atrophy (PRA) affects the cones and rods, causing deterioration and eventually blindness. Our Veterinary Vision Center team wants to provide information about this concerning condition, so you can determine if your cat is at risk.
Progressive retinal atrophy types in cats
PRA in cats can be inherited or acquired. Types include:
- CEP290 mutation — CEP290 is a gene that encodes for the centrosomal protein 290 kDa, and maintains the cilium in rod photoreceptors, which are important in sensation and signaling. CEP290 mutations cause autosomal recessive PRA, meaning a cat must inherit two mutated genes to be affected. This disease, which has been designated PRA-rdAc, typically begins around 1.5 to 2 years of age, with certain breeds, including Abyssinian, Somali, Ocicat, American curl, American wirehair, Bengal, Balinese, Cornish rex, munchkin, Oriental shorthair, peterbald, Siamese, and Singapura, at higher risk.
- CRX mutation — CRX is a gene that encodes for a transcription factor critical for retinal development. CRX mutations cause autosomal dominant PRA, meaning the cat has to inherit only one mutated gene to be affected. This disease, which has been designated PRA-Rdy, can begin to impair vision impairment as early as 4 weeks of age, and appears to be restricted to Abyssinian and Somali cats.
- Persian cats — An autosomal recessive PRA has been identified in Persian cats, but the causative gene has not been isolated. Vision impairment can begin as early as 2 to 3 weeks of age, and complete retinal degeneration occurs by about 4 months of age.
- Mixed-breed cats — Early onset PRA has been reported in mixed-breed cats, but is considered rare.
- Toxicity — Exposure to certain antibiotics, such as enrofloxacin and orbifloxacin, has been associated with PRA in cats. The incidence of these drug toxicities has decreased since enrofloxacin’s recommended dose was lowered to 5 mg/kg/day.
- Nutritional — Cats can develop PRA if their diet is deficient in the amino acid taurine. Taurine deficiency PRA begins in the retina’s center, and affected cats can use their peripheral vision in the early stages. All commercially available cat foods contain appropriate taurine levels, and this condition is most commonly seen in cats whose diet is not specifically formulated for felines.
Diagnosing progressive retinal atrophy in cats
If you believe your cat’s vision is impaired, your veterinarian may suspect PRA after a general ophthalmic examination, but retinal changes may not be apparent in the early disease stages. As the disease progresses, retinal changes include increased reflectivity of the tapetum lucidum, and changes in the optic nerve and the retinal blood vessels. More sophisticated testing using an electroretinogram (ERG) can confirm diagnosis, and is sensitive enough to diagnose PRA before cats show obvious signs. DNA testing can be performed on certain breeds to determine if they have mutations in their CRX or CEP290 genes.
Treating progressive retinal atrophy in cats
Discontinuing the drug in cases of antibiotic toxicity and correcting taurine deficiencies can stop PRA progression in affected cats. Unfortunately, no treatment is available for PRA caused by a genetic mutation. However, since scientists have identified gene mutations that cause two PRA forms, breeders can test their breeding stock to ensure they don’t perpetuate the disease.
Caring for a cat with progressive retinal atrophy
PRA is not a painful condition, and blind cats can live a long and happy life if certain provisions are made to make their life easier. These include:
- Keep your cat indoors — Blind cats cannot protect themselves from potential outdoor dangers, so keep them indoors to ensure they remain safe.
- Don’t rearrange your furniture — Blind cats memorize their surroundings, and rearranging the furniture can confuse them, and they will not be able to navigate obstacles.
- Safeguard dangerous areas — Pad sharp furniture edges and block off access to stairs to prevent accidents.
- Don’t move your cat’s belongings — Don’t move your cat’s belongings to ensure they can easily find their food bowl, water bowl, litter box, and scratching post.
- Talk to your cat — Blind cats can startle easily, especially if touched or approached without notice. Talk to your cat often, so they can track your location.
PRA is a concerning condition, but testing can ensure this disease isn’t passed to future generations. If your cat is experiencing vision problems, contact our Veterinary Vision Center team, so we can determine the cause of their sight loss.