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Do you suspect your dog is having vision trouble? Perhaps they’re nervous in dimly lit spaces or bumping into things in unfamiliar environments.
Although many conditions could be responsible for your dog’s vision loss, one possible cause is progressive retinal atrophy, also known as PRA. This is a genetic disease of the retina in the eye. Read on to learn more about progressive retinal atrophy in dogs.
According to Dr. Jerry Klein, Chief Veterinary Officer for the American Kennel Club, “Progressive retinal atrophy is, as the name implies, a gradual progressive degeneration of the photoreceptor cells in the retina, causing gradual vision loss, eventually leading to blindness.”
To fully understand the condition, it helps to appreciate the anatomy of the retina. This is a layer at the back of the eye that contains light-detecting cells called photoreceptors. When photoreceptors sense light, they trigger nerve impulses that pass through the optic nerve to the brain, which creates and interprets the visual . There are two main types of photoreceptors: rods and cones. Rods notice and track movement and work well in low light conditions, whereas cones detect color but need a lot of light to work. PRA impacts rods and cones.
Dr. Klein explains there are other causes of slowly developing blindness in dogs, such as glaucoma or cataracts, lens luxation, uveitis, or optic nerve tumors or disease. Therefore, it is important for your dog to get an accurate diagnosis. “Diagnosis of PRA requires a thorough retinal exam performed by a veterinarian who will often refer to a board-certified veterinary ophthalmologist. On some occasions, further diagnostics need to be performed to measure the electrical activity of the retina and evaluate possible development of other ocular conditions such as cataracts.”
What Age Does PRA Start in Dogs?
PRA’s progression is usually slow, with complete loss of vision taking place over a period of one to two years. But that can occur faster depending on the dog’s breed and the form of the disease. The condition can also strike dogs of almost any age. Dr. Klein says, “There are two basic types of PRA recognized in dogs. Early onset, also called retinal dysplasia, is usually found in young puppies around two to four months of age. Most PRA is seen in adult dogs from three to nine years of age.”
How Is PRA Diagnosed in Dogs?
A veterinarian can examine the retina with a magnifying instrument called an ophthalmoscope. This enables them to check the appearance of the retina, looking for telltale signs such as thinning of the retina or abnormal blood vessels.
These signs can be subtle. When in doubt, the vet will suggest referral to a veterinary ophthalmologist for a more detailed exam.
If a cataract is present, this stops the vet from seeing into the back of the eye. The trick is here to use a specialist test called electroretinography to map the health of the retina. Knowing whether or not the retina is working helps in determining whether it is worthwhile to remove the cataract.