What is Progressive Retinal Atrophy?

Progressive Retinal Atrophy (PRA) is a group of inherited degenerative diseases affecting the retina — the light-sensitive tissue at the back of the eye responsible for vision. In PRA, the photoreceptor cells (rods and cones) in the retina gradually deteriorate and die, leading to progressive vision loss and eventually complete blindness.

PRA is not a single disease but rather a collection of genetically distinct conditions that all result in retinal degeneration. Different breeds are affected by different genetic mutations, but the end result is the same: irreversible blindness.

Types of PRA

Early-Onset (Retinal Dysplasia/Degeneration)

  • Photoreceptors develop abnormally from birth
  • Vision problems appear in puppies or kittens (as early as 2–3 months)
  • Rapid progression to blindness

Late-Onset (Progressive Rod-Cone Degeneration)

  • Photoreceptors develop normally then degenerate
  • Vision problems appear in adult animals (typically 3–7 years)
  • Slower progression; night blindness is often the first sign

Symptoms

PRA develops gradually, and many owners do not notice the early signs:

  • Night blindness: Hesitation to go outside at dusk, bumping into objects in dim light
  • Dilated pupils (eyes appear to "glow" more in photos)
  • Increased eye "shine" (tapetum reflection more visible)
  • Reluctance to navigate unfamiliar environments
  • Bumping into furniture, walls, or objects (especially if rearranged)
  • Anxiety in new or dark environments
  • Cataracts may develop secondarily (cloudy eyes)
  • Complete blindness

Many dogs and cats adapt remarkably well to gradual vision loss, using their other senses (smell, hearing, whiskers) to compensate, which can mask the condition.

Affected Breeds

Dogs

PRA has been identified in over 100 dog breeds, including:

  • Labrador Retriever
  • Cocker Spaniel (American and English)
  • Miniature and Toy Poodle
  • Golden Retriever
  • Irish Setter
  • Dachshund
  • Siberian Husky
  • Cavalier King Charles Spaniel

Cats

  • Abyssinian and Somali (rdAc mutation)
  • Persian
  • Bengal
  • Siamese

Genetics

Most forms of PRA are inherited in an autosomal recessive pattern:

  • Affected: Two copies of the mutation (homozygous) — will develop PRA
  • Carrier: One copy of the mutation (heterozygous) — healthy but can pass it on
  • Clear: No copies — free of the specific mutation

This means two apparently healthy carrier parents can produce affected offspring (25% of the litter, on average).

DNA Testing

DNA tests are available for many breed-specific PRA mutations. Testing is:

  • Simple: cheek swab or blood sample
  • Available at any age
  • Definitive: Clear, Carrier, or Affected result
  • Essential for breeding decisions

Testing for Breeders

  • All breeding animals should be tested for PRA mutations known to affect their breed
  • Clear × Clear: All offspring will be clear
  • Clear × Carrier: No affected offspring; 50% will be carriers
  • Carrier × Carrier: 25% affected — should be avoided
  • Never breed two carriers or an affected animal

Treatment

There is no cure or treatment for PRA. The photoreceptor damage is irreversible. However:

  • Blind pets can live happy, fulfilling lives
  • Maintain consistent furniture placement
  • Use verbal cues and scent markers
  • Protect from hazards (pools, stairs, balconies)
  • Avoid startling the animal
  • Consider a "halo" harness for newly blind pets
  • Other pets in the household often serve as guides

Diagnosis

  • Ophthalmoscopic examination: A veterinary ophthalmologist can see retinal changes (thinning of blood vessels, tapetal hyperreflectivity)
  • Electroretinography (ERG): Measures the electrical response of the retina to light; can detect PRA before visible changes appear
  • DNA testing: Identifies at-risk animals before any symptoms develop
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