Progressive Retinal Atrophy in Pets
Quick Facts from a Veterinarian
Jennifer Hawkins, DVM
I have an antique domestic shorthair cat, "Maggie" (19 years and counting!), who is mostly blind. She certainly finds her food bowl just fine and seems to be able to negotiate obstacles fairly well. However, I have had to take some steps to ensure that she suffers minimal stress from her visual impairment including keeping her food, water and litterbox in the same place and using verbal cues to aid her when she's in a jam.
Many pets lose their sense of vision as a normal part of aging. This process is typically slow enough that most pets are able to adapt and compensate for their lack of vision, as has Maggie. Over the years, I’ve treated pets that have become so good at compensating for their impaired vision that they even fool their owners into believing they can still see. However, when dogs and cats lose their sight over a short period of time, it can be very distressing to both pet and owner.
Progressive Retinal Atrophy Can Lead to Blindness
There are many potential causes of the onset of blindness. An inherited disease that can affect younger pets known as progressive retinal atrophy, or PRA, is a condition in which dogs and cats lose their vision over the course of a few months to years.
First, there is typically a decreased ability to see in dim light or at night. Pets lacking the ability to see well at night will be timid about going outside at night or cautious when moving in dimly lit areas. They also are often reluctant to tackle obstacles such as stairs.
These signs are gradual at first but soon progress into the inability to see in daylight as well. Some animals have onset of blindness as early as eight weeks of age while others have a later onset at one to eight years of age.
What Causes PRA?
The retina, located in the back of the eye, is composed of two primary receptors: rods and cones. Rods are responsible for perceiving light impulses and cones perceive color.
In normal dogs, these receptors mature from birth to about 12 weeks of age. In some animals, these receptors never completely mature and may begin to degenerate at an early age.
The rods typically degenerate first, leading to the early symptom of night blindness. It is unclear what may cause these receptors to degenerate but it has been hypothesized that aberrant enzyme or protein may be to blame.
PRA is a genetic disorder that affects many breeds; however, an animal does not need to be purebred to suffer from PRA. Poodles, cocker spaniels, Dachshunds, Akitas and Abyssinian cats are among the many breeds that have been documented to develop PRA. Genetic testing for PRA has become available for many breeds.
Does My Pet Have PRA?
There are many varied causes of blindness including high blood pressure, neurologic disorders, liver disease, cataracts and retinal disorders.
If you suspect your pet may be suffering from impaired vision, schedule an appointment with your veterinarian as soon as possible.
In some cases, blindness can be reversed if the underlying cause is treated very early. In addition to an exam of the eyes, your veterinarian may also perform lab work testing or a blood pressure test to rule out other causes of blindness. Advanced testing by a board certified veterinary ophthalmologist may be required to make a final diagnosis.
How is PRA Treated?
Unfortunately, there is no treatment for PRA. However, the good news is that pets with PRA can live perfectly normal lives.
Pet owners merely need to be sensitive to the fact that their pet is blind and use verbal cues to encourage their blind pet to come or maneuver around household items. I recommend taking the same route when going on walks and not moving furniture or food bowls around, if it can be avoided.
While Maggie's condition was not caused by PRA, I do need to help her manage her blindness. To that end, I try to make sure that household items are always in the same place and I remove obstacles, such as a laundry pile, swiftly so that it doesn't trip her up later. I wish I could say that my three-year-old Abyssinian cat was as sensitive to Maggie’s visual limitations!
Dr. Hawkins received her veterinary degree from the University of California, Davis and practices in Orange County, Calif., where she also works at local animal shelters. In addition, she is an advisory faculty member for aspiring veterinary technologists at California State Polytechnic University Pomona. Dr. Hawkins is an active member of the Southern California Veterinary Medical Association where she serves on the Board of Trustees.