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It is a common myth that dogs only see in black and white. In truth, dogs possess some of the same nerve receptors in the backs of their eyes that humans have. These receptors are calledcones and allow dogs to see yellows and blues very well.
In fact, much of a dog’s eyesight is processed in the same manner as ours, so they can develop some of our common eye issues. But what happens when dogs begin to lose their eyesight? Is it simply old age, or could there be something else beneath the surface?
Dogs can develop cataracts when they age or because of certain illnesses like diabetes. Cataracts form in thelens of the eye, which is the clear disc-like structure that focuses light onto the back of the eye, aka theretina. The lens goes from being clear to cloudy and obstructs light passing through the eye, making it difficult to see anything except shadows.
Another eye condition callednuclear sclerosis causes the lens to harden with age so that it cannot flex and stretch as well as when your pup was younger. The lens is supposed to be flexible so that it can focus light from close up or at great distances. This inflexibility causes farsightedness, and it’s almost like your dog needs to have reading glasses!
Retinal diseases can also affect the way that your dog’s eyesight works. Traumatic injuries that causeretinal detachment mean that the layer in the back of the eye containing nerve receptors is no longer able to send electrical signals from the light that contacts it. Thus, your dog can no longer send these signals to the brain for processing. In other cases, dogs can inherit a kind of retinal disease known as progressive retinal atrophy which can affect both young and old dogs.
Progressive retinal atrophy (PRA) is a disease that causes the degeneration oratrophy of photoreceptor cells in the retina.Cones are one example of photoreceptor cells, and these are the kind that need light in order to work.
Like in humans, cones allow dogs to see color, and we can see more colors than dogs can because we have three main types (green, blue, and red) while dogs only have two main types (blue and yellow). Night vision is possible with photoreceptors known asrods, which help us see in the dark but can only show us black and white images.
As these rods and cones deteriorate in dogs with PRA, they gradually lose their eyesight. The rods tend to be the first affected cells, making it more difficult for your dog to see at nighttime. He may avoid dark areas on purpose! Your dog’s eyesight will worsen over time as the cones become affected, but this condition is painless so it can be difficult to notice immediately.
When young puppies develop PRA, it is known as retinal dysplasia because the termdysplasia refers to the abnormal development of cells. For older dogs who develop it, the disease is still referred to as progressive retinal atrophy.
Puppies can be diagnosed with retinal dysplasia as early as two to three months of age while dogs with PRA may be diagnosed from two to nine years of age. Senior dogs who develop acute vision loss may have a condition known as Sudden Acquired Retinal Degeneration or SARD. This can cause blindness over the course of days to weeks.
It is difficult to detect signs of retinal dysplasia early on because it can progress rather slowly. It can be as subtle as your dog having trouble jumping off of his bed or being reluctant to go downstairs. He may start to bump into things or have a hard time locating his favorite toys, so he will rely on his nose for assistance.
Dogs with retinal dysplasia may try to avoid going out for walks at night, and they may avoid dark spaces altogether.
When your veterinarian examines your dog’s eyes, she may notice an increase in the reflectivity of the back of the eye, or in some cases, vets can see areas of the retina that are detached. Many veterinarians will then recommend that your pup be evaluated by a veterinary ophthalmology specialist. Once there, the ophthalmologist can perform a confirmatory test known as an electroretinogram (ERG).
Unfortunately, there is no treatment for retinal dysplasia or PRA. Some veterinarians suggest that supplements and antioxidants can help with other aspects of eye disease, but they will not prevent PRA or retinal dysplasia from occurring. This is still an area of active research.
For now, it is best for owners to focus on keeping their dogs comfortable and to avoid moving furniture around so that their dog is less likely to bump into things.
Scientists have determined that there is a genetic component to these diseases. Therefore, if you plan on breeding your dog, ask your veterinarian about confirmatory testing to ensure that your pup doesn’t carry the gene responsible. Golden Retrievers, Cavalier King Charles Spaniels, Bedlington Terriers, and Cocker Spaniels have an increased risk for developing PRA.
Retinal dysplasia is a degenerative eye issue that causes the cells in the retina to atrophy. When adult dogs develop this eye disease, it is known as progressive retinal atrophy (PRA), but it is still referred to as retinal dysplasia in puppies. It is a non-painful illness but will cause gradual vision loss, and there is no way to treat or prevent it from occurring.
If you are planning on breeding your dog, make sure to have them evaluated for the gene responsible for causing it.
Meet The Author
Veterinarian
Erica has worked in the veterinary field since 2006, starting out as a veterinary technician before graduating from the UF College of Veterinary Medicine in 2013. As a general practitioner in an animal hospital, she has many interests and is especially interested in dermatology, cardiology, internal and integrative medicine.
