Dogs can adapt to loss of vision

10/19/2013

Dear Dr. Thompson: I have a wonderful black and tan mini dachshund who is almost 9 years old and was diagnosed last week with sudden acquired retinal degeneration syndrome (SARDS). Do you have any suggestions? I started noticing the changes in his eyesight in June when I would give him his treats after going outside, he would come in and stand by the pantry door for his treat and could not find it. Will SARDS shorten his life span?

Let me start by saying how sorry I am that your dog has lost his sight. Anytime there is a sudden change in vision an immediate trip to your veterinarian is indicated because some potentially serious underlying diseases may be the source of vision loss.

Your veterinarian will start by examining the entire eye and looking at the retina to eliminate cataracts or retinal detachment. Pressures inside the eye need to be measured because an increase in fluid called glaucoma can cause acute vision loss. High blood pressure can push fluid between the retina and the back of the eyeball, so that should be measured as well. Occasionally, you can see swelling of the nerve to the eye where it enters, which is a sign of more serious problems in the brain.

If all of those tests are normal, more specialized testing and referral to a veterinary ophthalmologist would be needed. Vision loss can occur anywhere along the neurologic pathway from the retina in the back of the eye up to the vision center in the brain. To eliminate those causes, often more involved testing like an electroretinogram (ERG) is needed.

You mentioned a diagnosis of sudden acquired retinal degeneration syndrome. In dogs with SARDS the ERG will be abnormal, which suggests the blindness is centered in the retina. Recently it has been determined that the pupil in dogs with SARDS will respond to a bright blue light but not a bright red light for reasons that are not fully understood. This syndrome has been linked to Cushing’s disease in dogs, which is a chronic overproduction of the stress hormone cortisol. A series of blood testing is needed to rule out this disease.

Certain breeds of dogs are also prone to progressive retinal atrophy that can mimic SARDS. This is a slow, progressive deterioration of the retina. Early signs include night blindness, but often the people only become aware when the disease has progressed to the point of loss of daytime vision. Dogs are frequently completely blind within one year of diagnosis, but there are some promising results with the use of a specially formulated anti-oxidant called Ocu-Glow that can slow the progression of the disease.

While blindness can be troubling at the beginning, I generally reassure people that dogs are adaptive and can do quite well without this sense. Since dogs have such a keen sense of smell, many sightless dogs can literally sniff their way through life. You will have to make some accommodations for his new situation and be careful in new environments, but he should do great. Good luck.

Questions for Dr. Gary Thompson can be emailed to askthevet@theblade.com or mailed to The Blade, Attn. Ask the Vet, 541 N. Superior St., Toledo, OH 43660. Dr. Thompson regrets that he cannot answer individual letters.