What is Progressive Retinal Degeneration?
Progressive retinal degeneration is a rare condition in the United States, but has been known to affect purebred cats including the Siamese, Persian, and the Abyssinian. The American curl feline, Tonkenese, American wirehair, Bengal cat, Oriental Shorthair and the Javanese/Balinese cat breeds have also held reports of contracting PRA, but are a lower risk.
Progressive retinal degeneration is characterized by a progressive degeneration of the retina, or photoreceptors (rods and cones in the retina) within the eye that aid in the ability to see. A healthy feline’s photoreceptors will fully develop at roughly eight weeks of age, giving the kitten the ability to see. However, a kitten affected with the mutated gene of progressive retinal degeneration will develop photoreceptors at the same age as a healthy feline, but they will degenerate with age. The degeneration process of the retina is slow occurring, but will often lead to total blindness as early as age three and as late as age five.
Symptoms of Progressive Retinal Degeneration in Cats
A feline with progressive retinal degeneration will progressively lose the ability to see and may become more cautious about her/his surroundings. The feline may take more time to assess a situation, such as walking into a room and meeting new people or other pets. The feline may bump into objects around the house or move slowly in order to identify the space in which she/he is occupying. Additional symptoms of progressive retinal degeneration a pet owner may note include:
- Pupil dilation
- Nervousness with other pets/animals
- Visual deflect at night
- Increased tapetal reflex that can be seen through the pupil
Causes of Progressive Retinal Degeneration in Cats
Progressive retinal degeneration in cats is an inherited, autosomal recessive disorder, which requires two copies of the mutated DNA to affect the offspring. Meaning, if only one parent possesses the gene, the infant will not be affected by PRA. However, if both parents possess progressive retinal degeneration genetics, the kitten will be born with PRA compromised DNA.
Progressive retinal degeneration itself is caused by a single nucleotide mutation of the gene known as CEP290, which produces a defective cellular protein. The cellular defect inflicts the fetus during development, targeting the retina’s rods and cones, which reflect light-- providing the ability to see.
Diagnosis of Progressive Retinal Degeneration in Cats
A differential diagnosis, which is the act of testing and excluding possible causes of the feline’s symptoms, is the likely method your veterinarian will take to diagnose progressive retinal degeneration. The doctor will begin the diagnostic process by reviewing your cat’s medical history and conducting a physical examination. Upon physical examination, your vet will determine which ophthalmic tests he/she should conduct to locate the problem. Common ophthalmic examinations performed to detect progressive retinal degeneration include:
- Tonometry (measurement of intraocular pressure)
- Schirmer test (evaluate tear production)
- Fluorescein staining to detect eye trauma
- Pupillary light reflex test (the act of placing light in the eye to observe dilation and contractions of the eye’s pupil)
Progressive retinal degeneration itself can be detected through an electroretinogram test. Often conducted by a veterinary ophthalmologist, an electroretinogram uses flashes of light to evaluate the functionality of the eye’s photoreceptor cells during stimulation. A confirmed diagnosis of progressive retinal degeneration is then made when the results come back as abnormal, meaning the retina is diseased and unresponsive.
Treatment of Progressive Retinal Degeneration in Cats
Progressive retinal degeneration has no available treatment to cure, slow, or prevent the degeneration of the retina. The degeneration process is occurring due to mutated DNA, which cannot be readily accessed as this is the feline’s genetic makeup.
The veterinarian may advise that you have the affected cat spayed or neutered to prevent passing the progressive retinal degeneration gene on to offspring. Progressive retinal degeneration in cats leads to blindness, but a blind cat can have a better quality of life if accommodated by the pet owner. Talk to your veterinarian about the best way to aid a feline who is losing the ability to see.
Recovery of Progressive Retinal Degeneration in Cats
Progressive retinal degeneration in cats can be tested with a simple cheek swab and laboratory examination. Feline breeders who enter Siamese, Persian or Abyssinian felines into their breeding program should test cats prior to breeding. Any feline with a positive PRA test result should be spayed or neutered to prevent further generations from progressive retinal degeneration.