Canine multifocal retinopathy is an inherited eye condition that affects the retina. In the Coton de Tulear, the form seen is CMR2, caused by a mutation in the BEST1 gene [citation:2]. It is one of the eye issues breeders are encouraged to test for.
What it looks like
In an affected dog, patches of the retina become elevated, like small blisters. These lesions are usually present in both eyes and vary in size and position. In Cotons, they often contain a clear fluid, though sometimes material builds up and gives them a grey, tan or pink colour [citation:9].
The disease usually develops in young dogs, between 15 weeks and one year of age. After the first year, the lesions tend to stay the same in size and colour. The fluid often gradually disappears after about four or five years [citation:9].
Does it cause blindness?
In most cases, no. Early on, dogs show no obvious vision problems despite the unusual look of the retina. Some degree of retinal degeneration can happen over time, but CMR does not typically lead to blindness or major vision loss [citation:7][citation:9]. This is different from some other eye diseases, such as PRA, which do progress to blindness.
That said, any change in the retina is worth monitoring. A veterinary ophthalmologist can check the eyes and give you a clear picture of what is happening.
How it is inherited
CMR is inherited in an autosomal recessive way [citation:5][citation:9]. A dog needs two copies of the mutation to be affected. A dog with one copy is a carrier. Carriers do not show signs and have normal vision, but they can pass the mutation to their puppies.
If two carriers are bred, each puppy has roughly a 25 percent chance of being affected, a 50 percent chance of being a carrier, and a 25 percent chance of being clear [citation:7].
DNA testing
A DNA test is available for CMR2. It uses a cheek swab or a blood sample and tells you whether a dog is clear, a carrier, or affected. The test looks specifically for the BEST1 mutation found in Cotons [citation:2].
Results can be registered with the OFA. If you are buying a puppy, ask the breeder whether the parents were tested and whether you can see the results.
Breeding advice
The simplest and safest approach is to breed only clear dogs to clear dogs. All puppies will then be clear.
If a carrier is used, it should only be paired with a clear dog. This avoids producing affected puppies, though some of the litter may still be carriers. Breeding two carriers is not recommended [citation:2][citation:7].
Because CMR does not usually cause blindness, some breeders may treat it as a lower priority than other conditions. The club still encourages testing so that breeders can make informed choices and avoid producing affected dogs where possible.
What the club recommends in 2026
As of 2026, CMR2 DNA testing is widely available and is part of the health screening the club encourages for breeding Cotons. If you have questions about a test result, or you are not sure what it means for your dog, please write to us, call us, or come and visit us at a club event.
Sources: OFA/ACVO Blue Book, OMIA, Wisdom Panel, Grahn et al. (2008).
