Progressive retinal atrophy (PRA)

How it presents at home

The rod cells that handle low light degenerate before the cone cells that handle daylight, so the first change is reluctance in the dark. Owners notice a dog hesitating on unlit stairs, refusing the garden at night, or bumping into things only after sundown, often for months before day vision is affected.

Because it is painless and slow, and because animals compensate with memory and smell, the loss is frequently missed until something changes: moving house, rearranging furniture, or a visit somewhere unfamiliar. Full blindness usually follows over one to two years, though this varies by breed and by which form of PRA is involved.

• A greenish, unusually bright eyeshine, from the reflective layer showing through a thinned retina.
• Dilated pupils that stay wide in bright light.
• Hesitation at kerbs, thresholds and stairs, worse in dim light.
• Cataracts developing later, which can appear alongside advanced PRA and complicate the picture.

Diagnosis and genetics

Diagnosis is a retinal exam, usually by a veterinary ophthalmologist, sometimes with an electroretinogram that measures the retina's electrical response and can detect the disease before an owner sees anything. More than a hundred breeds have a documented form, and the forms are genetically distinct, which is why a test validated for one breed says nothing about another.

Most forms are autosomal recessive, meaning a dog needs two copies to be affected and a single-copy carrier is entirely normal. This is why carriers can be bred responsibly, unlike a dominant disease: a carrier paired with a clear dog produces no affected puppies. Ask which specific test was run rather than whether the line is clear.

Living with a blind dog or cat

This is the part owners consistently dread more than the animal experiences. Vision is not the primary sense for either species, the loss is gradual enough to allow adaptation, and most affected animals continue an ordinary life.

• Keep furniture, food and water where they are. Consistency is the whole strategy.
• Talk before touching, so the animal is never startled awake or approached silently.
• Block stairs, pools and drops during the adjustment period.
• Textured mats at thresholds give underfoot landmarks.
• Scent-led and sound-led toys keep enrichment going when visual toys stop working.

Why it matters

PRA is the clearest argument for buying from breeders who publish test results. It cannot be treated, cured or slowed, so every bit of leverage sits before the animal is born. For an owner already facing it, the useful reframe is that this is a slow adaptation rather than an emergency, and that most of the practical work is arranging a stable environment rather than buying anything. The genuine hazard is a sudden change of setting, not the blindness itself.