Sudden Acquired Retinal Degeneration (SARD) is often labelled as an autoimmune disease. Let me walk you through why this cannot be the case. It’s a simple concept.
Concept 1: SARD dogs CAN regain vision
Despite the often-repeated mantra that blindness is permanent in SARD, reports have been coming out since 2006 demonstrating that SARD dogs can regain vision. My own website continues to document these cases. Dr. Grozdanic (Iowa State University) demonstrated this in 2007. And if you get veterinary ophthalmologists into a private conversation, many will admit that they have witnessed some reversal of blindness during their career.
Blind dogs can see after new ISU treatment*
*As part of their treatment, these dogs are typically prescribed long-term daily prednisone which acts as a cortisol replacement.
Concept 2: In autoimmune disease, retinal cells are destroyed which causes blindness
Pay attention to the sequence of events in autoimmune disease:
A) The body initiates an autoimmune attack
B) This is followed by retinal cell destruction
C) Which is followed by blindness.
Therefore, in total blindness, all retinal cells have been destroyed. That’s the theory.
Note: In humans with autoimmune retinal diseases, the vision loss is not as sudden as in SARD. Treatment for human autoimmune retinal disease is geared toward reducing destruction of remaining retinal cells — remaining cells and REMAINING VISION.
Concept 3: Retinal cells do not regenerate
Now IF the autoimmune theory was true for SARD, destroying retinal cells prior to the vision loss, then in order for these dogs to regain vision — which some obviously do — these dogs would have to produce new retinal cells.
But therein lies the problem. Mammals cannot regenerate retinal cells. Only fish and reptiles can do this, not dogs.
Concept 4: Based on the theory of autoimmune disease, SARD cannot be autoimmune
If autoimmune retinal disease destroys cells then they cannot regain vision. Since we know that these dogs CAN regain vision, SARD is not likely to be an autoimmune disease. SARD is some other type of disease process such as a seizure of the retina.
Excitotoxicity (a type of seizure activity) was proposed as a mechanism in SARD over 30 years ago. (Riis, 1990; Abrams and Dreyer, 1993) I have long suspected this is why some dogs also lose their sense of smell. Like the retina, the olfactory nerves experience some seizure activity.
The excitotoxicity theory suggests that:
A) Retinal cells have a seizure
B) Visual function is lost suddenly
C) If the seizure is halted, some retinal cells can regain function
D) If the seizure remains unchecked, retinal cells are destroyed
Note the difference in the sequence of events between this theory and the autoimmune theory. In this theory, cell destruction happens at the very end of the sequence. And this explains why there is a window of opportunity to restore some retinal activity and vision. The cells are not dead early in the disease process, they are just having a seizure.
IN REVIEW
The autoimmune theory suggests that retinal cells are destroyed resulting in blindness. In order to regain vision after autoimmune destruction, dogs would have to regenerate retinal cells. But no mammal can do this. So autoimmune disease is an unlikely cause of SARD.
Excitotoxicity appears to disrupt communication with the visual cortex of the brain. Vision is suddenly lost. If the seizure continues unchecked, retinal cells are THEN destroyed. But before then, there are things that can be done to help these dogs. Correct the hormones. Protect the retina. Stop the seizure.
Look to a holistic veterinarian or a general practice veterinarian with whom you have a good working relationship. They will be the most helpful in getting your dog treated.
I hope this helps you and your dog.
Best,
Caroline
Riis RC. EM observations of a SARD case (abstract). 21st Annual Meeting of the American College of Veterinary Ophthalmologists 1990; 21: 112–113.
Abrams KL, Dreyer EB. Excitotoxicity in canine sudden acquired retinal degeneration. Investigative Ophthalmology and Visual Science 1993; 34(Suppl): 3297.
