In mammals, having eyes means the important advantage of possessing vision—the immense talent of photoreception. This is the ability to absorb light waves, convert them into electrical signals, and process them to create an image.
It’s a process that seems almost magical.
However, this incredible organ can suffer various issues in dogs, and one of them is called progressive retinal atrophy (PRA).
The Retina and Its Atrophy
The retina is a tissue found on the inner surface of the eye. In simple terms, it consists of several layers of interconnected neurons.
Among these are the rods and cones, which are light-sensitive cells responsible for initiating the cascade of signals that ultimately allow your dog to see where you left that unguarded piece of cheese.
Progressive retinal atrophy is a group of genetic eye diseases in dogs that affect, as the name suggests, the retina. These are hereditary conditions. Although cats can also suffer from it, PRA is more common in dogs and is comparable to retinitis pigmentosa in humans.
This disease causes retinal degeneration in dogs, affecting both eyes, and can eventually lead to blindness.
The first photoreceptors affected are the rods, which are responsible for low-light, black-and-white vision. For this reason, one of the earliest symptoms is night blindness in dogs.
Affected animals will avoid dark areas and show less confidence at night. However, dogs do not rely on vision as much as we do, which helps them adapt better to vision loss, though it complicates early detection.
As the disease progresses, cones are also destroyed, leading to complete blindness.
Variety of Dog Breeds and Retinal Atrophy
As we mentioned before, dogs, as a species, are one of the organisms with the greatest genetic variety. This has also given them a wide range of progressive retinal atrophies, with different genetic variants responsible depending on the breed.
While some breeds with higher predisposition are known, these are NOT the only ones. If a dog does not appear on these lists, it does not mean its owner can dismiss the possibility of developing problems.
In most cases, it is an autosomal recessive trait. A carrier animal with only one abnormal gene does not show the disease (although it may experience minor discomfort).
There are two exceptions to this rule:
- X-linked progressive retinal atrophies. This is characteristic of the Siberian Husky, although it appears that Samoyeds may also suffer from it. In this case, if the dog is male, it does not matter whether the gene is recessive or dominant. With only one X chromosome, the dog will always have the disease.
- An autosomal dominant progressive retinal atrophy. This is characteristic of the English Mastiff, but other breeds derived from this mastiff, such as the Bullmastiff, may also have it.
Other dog breeds with progressive retinal atrophy and a higher probability of carrying mutated genes include the Labrador and Golden Retriever, English and American Cocker Spaniels, Australian Cattle Dog, Tibetan Mastiff and Spaniel, Basenji, Irish Setters, Cardigan Welsh Corgi, and Papillon.
The disease does not progress in the same way in all cases. Not only are these breeds more prone to having mutated genes, but the age of onset and the rate of retinal degeneration also vary among breeds.
This variation is due to the more than 20 genetic variants currently known to cause the disease. Depending on the variant, its progression will differ.
For example, in Retrievers, the gene SLC4A3 is often responsible for retinal atrophy (accounting for 60% of cases). For retinal atrophy, the gene TTC8 represents another 30%.
The range of conditions under PRA is quite extensive.
One of the simplest classifications is into dysplastic and degenerative forms. In the dysplastic form, the retina develops abnormally from the start, causing blindness much earlier than in classic PRA. In the degenerative form, the tissue initially develops normally but begins to degenerate over the dog’s lifetime.
Sometimes, PRA and generalized progressive retinal atrophy are confused. Generalized PRA is the most common of all PRA types and could be considered the most representative, as it is degenerative, affecting both photoreceptors, and common in many dog breeds.
However, generalized PRA is a type of PRA and does not include all diseases within this category.
Seeing What Prevents Seeing
There are symptoms of retinal atrophy in dogs. As we mentioned, the first clue to the disease is the loss of night vision, or nyctalopia. Although the changes are not as pronounced as in cataracts, a greater dilation of the pupil can be observed, allowing the eye to capture more light.
A professional examination will detect other indicators of retinal atrophy, such as narrowing of blood vessels and decreased pigmentation. A simple visual exam of the retina can reveal it, and an electroretinography test can confirm it.
Physical changes are accompanied by behavioral changes. Not only may the dog display insecurity in dark areas, but it may also become hesitant on stairs and frequently bump into things if furniture is rearranged. Dogs memorize the arrangement of objects in the house, so moving items around while they have limited vision may lead to accidents.
The disease is not painful, which contributes to it going unnoticed, as the animal will neither resist nor complain.
Unfortunately, like most genetic diseases, there is currently no cure. Vision loss occurs one to two years after diagnosis.
On the other hand, there are treatments to help them cope with the issue, and they do not rely on vision as much as we do.
If only we could navigate by sniffing the ground, but that talent is reserved for them.
There are a series of simple recommendations to help your pet:
1. In the early stages, add extra lighting both inside and outside the house, if possible.
2. Keep the house’s interior layout unchanged, in line with the mental map the animal has of each room.
3. Block off stairs, balconies, and other risky areas.
4. Walk the dog with a short leash and close to you, especially at night and/or in unfamiliar places.
This is a condition where genetic testing is very useful. First, because the main genetic variants responsible for the disease in each breed are well known. Prevention before treatment. Second, because if two dogs are carriers, they should NOT be bred together. Avoiding these crossings is one way to eliminate the disease.
For both reasons, the Koko Genetics genetic test is a safe choice to identify these abnormal genes.