Your dog (or cat) is going blind.
You have no experience with a blind pet.
You don’t know what to expect.
You don’t know how to cope.
Fortunately, your pet does.
Our only remaining dog, Pearl, is experiencing a degenerative retinal condition that is causing a gradual deterioration of her vision. Fortunately it is so slow that we notice a change only every few months.
I say “remaining” dog because we lost our other dog, Peyton, Pearl’s littermate, to liver disease several years ago. We still miss him terribly. Pearl and Martha help tremendously with the hurt.
Our first clue that something was wrong with Pearl’s vision was a usual and common condition of aging, Lenticular Sclerosis. Lenticular Sclerosis is a hardening of the lens that occurs as part of the aging process. As the lens hardens it tends to become cloudy, a little opaque. It is this opacity that causes pet owners to see a little grey reflection when light hits a pet’s eyes just right. Pet owners often ask us whether the pet has cataracts. While Lenticular Sclerosis can progress to a true cataract, in this stage light still goes through the lens and images are still fairly clearly formed on the retina. As often as not, Lenticular Sclerosis does not progress to cataract formation during a pet’s lifetime.
Lenticular Sclerosis also occurs in people around age 40. It’s what causes us to have “arms too short,” or lose our ability to focus close up.
Almost as a matter of routine I made arrangements for Dr. Laurence Galle, a board-certified veterinary ophthalmologist practicing here on the Mississippi Gulf Coast, to evaluate Pearl for possible future cataract surgery. It was during his thorough examination with specialized equipment that he discovered her poor vision was unrelated to her lenses.
Instead, Pearl has Progressive Rod-Cone Degeneration, a form of Progressive Retinal Atrophy or PRA.
Just as in people, dogs’ and cats’ retinas include two types of photoreceptor cells: rods and cones. Rods work best in minimal light and convey little color, mostly blue hues. Cones are receptive only to bright light, and offer animals the ability to see a wider range of colors and more detail than rod vision.
Rods and cones are highly active metabolically and even have controlling effects on other cells in the eye.
PRA results first in damage to the rods and causes nyctalopia, or reduced visual capability in low light. It is sometimes incorrectly referred to as night blindness, although partial loss of vision occurs before total blindness.
As rods degenerate and die, they create a toxic environment in the retina which damages the cones, also. Eventually the carnage affecting both rods and cones results in total blindness, regardless of the amount of light present.
With the inflammatory process of PRA releasing rod and cone cells’ internal contents, the lens of the eye may respond by forming a cataract. The presence of cataracts in eyes already affected by PRA is an inconsequential finding, as removal of the cataracts will not improve vision and is not recommended.
Diagnosis of PRA may be straightforward in the affected animal by way of a funduscopic (retinal) examination by a board-certified veterinary ophthalmologist. The usual onset of clinical signs occurs between three and seven years of age. Some patients may be diagnosed before signs are present. Some, more subtle cases, may require ERG or ElectroRetinoGraphy to stimulate the retina under general anesthesia. Early cases in very young animals may still be missed.
Progressive Rod-Cone Degeneration is a gene-defect condition and transmissible to offspring. A genetic test is now available for some breeds and will determine whether a patient is normal (does not carry the gene), a carrier (vision is not affected but the offspring of this individual may be affected) or is an active case whose rods and are now or will be degenerating.
Puppies in the latter two categories must be surgically sterilized so that they cannot pass on the defective gene.
Dr. Galle has this to say about treatment: “Unfortunately, there is no cure for any of the diseases in the progressive retinal atrophy complex. There are limited anecdotal reports that antioxidant supplementation may slow the progression of the disease, but controlled studies do not support the effectiveness of antioxidant therapy. Furthermore, oversupplementation with antioxidants may be harmful to patients. I discourage use of such antioxidant therapies, because of the lack of proven effect and the potential for harm. However, due to the feelings of helplessness that many pet owners have when their pet is diagnosed with PRA, we often find it necessary to try to provide some sort of therapy that may help, despite the lack of evidence supporting its efficacy. In any case, use of such antioxidant therapy should be only under the recommendation of a veterinarian.”
PRA is degenerative and there is no specific treatment. Under Dr. Galle’s guidance we are using a supplement containing lutein, vitamins A, C and E and several other ingredients believed to help with conditions such as macular degeneration in people. As dosages will vary among patients, you, too, should follow Dr. Galle’s advice and do not begin supplementation except under your veterinarian’s watchful care.
Pearl’s diagnosis was over a year ago and now her vision is about 20% worse than it was then. Prior to deterioration of her vision Pearl was attentive to every human’s location. She was quick to move out of the way when she saw someone walking toward her. Now, however, she simply doesn’t see people coming. Add the effect of age-related hearing loss and she often doesn’t know that anyone is even in the room with her.
Pearl is startled more easily than she used to be, so she’s “jumpier.” She still feels vibrations quite well, so when a sharp noise occurs (such as a cabinet door that accidentally slams), it causes her to wheel around as if something is after her. Obviously, such events are heartrending, so we avoid pops and snaps when we can, but Pearl is resilient and she copes well.
We also notice that she is less courageous than she used to be. When Pearl goes outside to use the bathroom she looks around to be sure that one of us is with her. She used to go out all alone, but we no longer allow her to do so since she sometimes loses her sense of direction and goes toward the street when it’s time to come back indoors.
Dr. Galle adds, Blind pets “cannot easily find their way out of a street if a car is coming. It is imperative that blind pets who are kept outdoors live in a fenced yard without access to a swimming pool. Even if a dog can swim, he cannot easily find his way out of a pool if he cannot see. I had a blind patient drown in this very scenario last year. Is was a very sad moment for my clients and for me.”
Brenda Randolph says, “Part of our home is elevated above ground level. We fear that Pearl may lose the ability to see the edge of the deck and fall, so we never let her go to that part of the house any more. If you have a deck, balcony or mezzanine in your home, you should follow similar precautions.”
Amazingly, dogs cope with blindness so well that gradual-onset blindness is something we often have to inform pet owners about, instead of the other way around. If a dog’s environment remains unchanged he may so totally acclimate to his blindness that his family is unaware that he gets around by feel and sound instead of by sight. Then, during a routine physical examination we may discover blindness the family was unaware of.
Rearrange furniture, however, forcing him to renegotiate, and his handicap shows through.
Dr. Galle points out that not all of the news is bad, and offers this encouragement: “There are training techniques to help blind pets learn new environments, and most pets can adapt will with training provided by a dedicated owner. A good resource for such training techniques is Living With Blind Dogs: A Resource Book and Training Guide for the Owners of Blind and Low-Vision Dogs, Second Edition, by Caroline Levin. Most importantly, I like to reassure pet owners that blind dogs can still have a great quality of life. They still love us and respond to our affection. I have blind patients that still play fetch, chase balls, chase other dogs. I know a veterinary ophthalmologist who owned a hunting Labrador Retriever with PRA. After his dog became completely blind, he continued to take his dog quail and pheasant hunting. This was not the waterfowl hunting for which his retriever was originally trained, but it was a way he could safely take his dog hunting. The lab would “work close” to him, alert him to the presence of game, and with the use of voice commands and his smell, would retrieve the downed game.”
Our many thanks to Dr. Laurence Galle for his time and expertise in diagnosing Pearl’s condition and for providing information for this article.