Progessive Retinal Atrophy (PRA)
There are many causes of blindness in dogs and if you suspect that your dog’s eyesight is deteriorating you should contact your vet immediately. Some of the causes of blindness can be treated and vision can be retained. Sadly, other causes like PRA cannot be treated but your vet may be able to help you cope with living with a blind dog.
PRA (also known as generalised progressive retinal atrophy or GPRA) describes a group of inherited eye diseases of dogs. PRA leads to slowly progressive blindness over a period of months or years.
PRA has been reported in more than 100 different dog breeds, but in the UK it is most commonly seen in poodles (miniature and toy), cocker spaniels and Labrador retrievers.
The earliest sign is usually poor vision at night or in dimly lit surroundings. Affected dogs may become more cautious or nervous about going outside after dusk. Over time, vision deteriorates further until day vision also becomes affected. Affected dogs may lose peripheral vision and develop tunnel vision.
The pupils may appear dilated and increased eye shine may be evident. In some dogs cataracts may develop secondary to the PRA so that the eyes appear cloudy.
The age at which signs of PRA develop varies between breeds. Typically, PRA affects middle-aged dogs (3-8 years old) although in some cases clinical signs may not develop until later in life. In a few breeds (such as the miniature schnauzer) signs may develop earlier.
Confirmation of PRA is made by examining the back of the eye with an ophthalmoscope to look for characteristic signs of retinal degeneration. If the retina cannot be examined (e.g. if secondary cataracts are present) then a test called an ERG (electroretinogram) may be performed. Your vet can refer you to a specialist veterinary ophthalmologist for this test.
DNA tests are also available for some breeds of dog. DNA tests are particularly useful in young dogs or those which may be used for breeding because they can identify affected dogs before they develop signs of PRA. They can also identify carrier animals. Carrier dogs will not develop PRA themselves but may pass the disease on to their offspring.
Unfortunately there is currently no effective treatment for PRA and affected animals will become totally blind, usually over a period of months to years. Because of the slow progression of the disease, however, most dogs learn to adapt to their blindness and continue to lead contented lives.
As PRA is an inherited disease, affected animals should not be used for breeding.
