What is Canine Multifocal Retinopahty (CMR and sometimes MR1)?
CMR causes blister-like defects in the retina. CMR can be detected by 4 months of age. It may gradually progress or may go away. Diagnosis by exam can be difficult; CMR may be described as retinal dysplasia or retinal folds, both of which are reported in Aussies. In rare instances the disease can impact vision. Some dogs with CMR may not show signs.
How do I know if my dog has retinal folds or CMR?
They can only be found with an eye exam conducted by a veterinary ophthalmologist. If the dog has CMR the vet may note it as retinal folds or as retinal dysplasia. ASHGI strongly recommends that if your dog is diagnosed with either retinal folds or retinal dysplasia that you have the DNA test for CMR done on the dog.
Will retinal folds go away?
Sometimes, especially in young puppies.
What does it mean for my dog if it has CMR?
Most dogs with CMR have normal vision. A few dogs will have diminished vision due to CMR. There is no treatment but the disease does not cause any pain. You would need to make sure the dog is not put in situations where it might be injured or frightened by hazards it cannot see.
Is CMR hereditary?
CMR is due to a recessive gene mutation. Affected dogs will have two copies of the mutation. Each of an affected dog’s parents must have at least one copy.
How common is CMR in Aussies?
This hasn’t been determined but based on ASHGI data about 1% may be affected. It is very possible that cases of retinal folds and retinal dysplasia reported in Aussies are actually CMR. If so roughly 1% have CMR and around 18% more are carriers.
Is there a DNA test and what do the results mean?
If a dog with folds is a potential breeder, you might want to get it tested. Parents and full and half siblings of dogs affected with CMR who might be bred should be tested. Two copies of the mutation mean the dog is affected with CMR; dogs with one copy are carriers.
What does CMR mean for my breeding program?
Dogs that have diminished vision due to CMR should not be bred. As long as vision isn’t impacted the dog may be bred. Dogs that have one or two copies of this mutation should only be bred to dogs that have tested clear.