What causes sudden acquired retinal degeneration in dogs and is there any treatment?
Original Question: Lucky has been a very active and healthy dog. This past Saturday we noticed that Lucky was not going directly for treats. Instead he was sniffing around the treat first. This concerned us and we then started tossing treats on the floor just out of his reach and again he would not see the treats and he was sniffing to locate them. We took Lucky to a vet and they could not see problems with the eyes themselves but confirmed that he was blind in both eyes, and that we could be dealing with sudden acquired retinal degeneration syndrome (SARDS). We are currently waiting to go see a board certified ophthalmologist. I have two questions: What would be the likely causes of sudden blindness? I did see on Google that Heartgard has been linked to sudden blindness in dogs, is this true? Lucky just started on Heartgard this past August. Are there any treatments medically confirmed or otherwise that might help Lucky regain any of his sight back? - Paul
So there are potentially a number of causes of sudden blindness in dogs. So SARDS or sudden acquired retinal degeneration syndrome is certainly one but we can also get cataracts due to diabetes, we can get retinal detachment, which can be an immune-mediated problem. So the body’s immune system isn’t working as it should do, or it can also be blood pressure related, which is generally a result of kidney disease. We can also have glaucoma, which is an increase in pressure within the eye causing blindness, that’s often very painful and can be quite obvious certainly when it’s advanced and we can also get tumors in the eye that can cause blindness and there’s a whole heap of other things we can get such as brain lesions.
Heartgard contains ivermectin and ivermectin toxicity can cause sudden blindness. However, at normal doses and even at 10 times the normal dose Heartgard has been found to be safe even in Collie’s, which is a breed that is known to be more sensitive to the effects of ivermectin than other breeds of dogs. So with normal Heartgard treatment, it’s really highly unlikely to be responsible for this sudden blindness or for any blindness unless a really serious overdose was given or there was another exposure to a different source of ivermectin. So ivermectin is found in other parasite control products and also some livestock products and that kind of thing. So if there’s been any exposure to those chemicals then that’s certainly a potential and one to bear in mind.
The sudden acquired retinal degeneration syndrome is actually a really rare disease and we don’t know why it happens. It could be immune-mediated, so again, the immune system isn’t working properly. It could be due to something called Cushing’s disease or hyperadrenocorticism, which is an abnormality in our bodies, either in the pituitary or adrenal gland and blindness generally occurs in less than one month. So your dog certainly ticks that box and it is often accompanied by an increase in thirst and an increase in hunger.
So that would be interesting to know if that was the case and unfortunately there’s no medical or surgical treatment that we are aware of at this stage to treat that. That could mean that a dog is blind permanently, but it’s important to think that in fact, many dogs can cope very well with being blind. Some will struggle and my experience is that those dogs that have become blind very suddenly and certainly with something like diabetic cataracts that can happen in 24 to 48 hours in some cases. So it can come on really suddenly and that’s in both eyes and they may struggle to cope a little bit more. Those dogs that become blind maybe a little bit more slowly, they can cope very well but we need to be keeping the environment stable. So we don’t want to be moving furniture, changing the floor plan of the house, just so that your dog is very familiar with their surroundings.
We want to install stair gates if you’ve got any stairs so that they can’t either fall downstairs or they can’t climb up and get themselves into trouble and that can cause them some serious injuries. You can also get something called a halo harness when your dog is out. So that is a little harness that they wear and it’s got a plastic halo rim that goes around their face so that when they are coming up to bump into something, then that actually knocks into that halo, the dog feels it and they’re not going to bump into it and hurt themselves. Talking to your dog is also important. Just don’t sneak up on them because that can give them a great deal of anxiety.
So while it can be understandably very distressing for any dog that goes blind suddenly, they often will cope very well with a few changes and a few adaptations to their lifestyle.
I hope this helps.
Dr. Alex Avery
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