Health Screening Guide
CMR1 in French Bulldogs
Canine Multifocal Retinopathy explained: retinal lesions, how they affect vision, and how responsible breeders use DNA testing to stop CMR1 from reaching the next generation.
Check Your PairingWhat Is Canine Multifocal Retinopathy?
Canine Multifocal Retinopathy Type 1 (CMR1) is an inherited retinal disorder caused by a mutation in the BEST1 gene. It causes multiple focal lesions — small, raised areas of abnormal tissue — to develop in the retina, the light-sensitive layer at the back of the eye.
Unlike JHC, which attacks the lens, CMR1 targets the retina itself. The lesions typically appear in puppies between 8 weeks and 4 months of age. Most lesions stabilize by adulthood and do not progress, meaning affected dogs usually retain functional — if slightly compromised — vision throughout their lives.
CMR1 is a recessive trait. A dog needs two mutated copies (CMR1/CMR1) to develop lesions. Because many affected dogs show few outward symptoms, the condition often goes undiagnosed unless a breeder specifically tests for it. That makes pre-breeding screening even more critical.
Understanding CMR1 Lesions
Focal Lesions
Small, discrete raised spots in the retina. These are the most common presentation and often cause minimal vision disturbance.
Geographic Lesions
Larger confluent areas where multiple lesions merge. These can cause more noticeable blind spots in the visual field.
Retinal Detachment
In severe cases, extensive lesions can lead to partial retinal detachment. This is rare but causes significant vision loss.
CMR1 Breeding Safety Chart
N/N x N/N100% clear — no CMR1 mutation in any puppy
N/N x N/CMR150% clear, 50% carriers — no affected puppies
N/CMR1 x N/CMR125% affected, 50% carriers, 25% clear — AVOID
N/CMR1 x CMR1/CMR150% affected, 50% carriers — NEVER BREED
Screen for CMR1 Before You Breed
Our DNA Calculator checks CMR1, DM, HUU, and JHC in a single analysis. Know every retinal and health risk your pairing produces before any puppies are conceived.
Open the DNA CalculatorFrequently Asked Questions
What is CMR1 in French Bulldogs?
Canine Multifocal Retinopathy Type 1 (CMR1) is an inherited eye disorder that causes multiple retinal lesions — raised areas of abnormal tissue — in the back of the eye. It is caused by a mutation in the BEST1 gene. Most affected dogs retain functional vision but may have areas of reduced sight.
How is CMR1 inherited in Frenchies?
CMR1 is an autosomal recessive trait. A French Bulldog must inherit two mutated copies of the BEST1 gene (CMR1/CMR1) to develop retinal lesions. Dogs with one copy (N/CMR1) are carriers — they have healthy retinas but pass the mutation to about 50% of their puppies. Clear dogs (N/N) are completely unaffected.
What are the symptoms of CMR1 in French Bulldogs?
Most dogs with CMR1 show no obvious behavioral symptoms because vision loss is usually mild and localized. Lesions are detected during a veterinary eye exam with an ophthalmoscope. In rare severe cases, dogs may show hesitation in unfamiliar environments or difficulty tracking moving objects.
Can CMR1 be treated?
There is no specific treatment for CMR1. Most lesions stabilize after puppyhood and do not worsen significantly. Affected dogs typically live normal lives with mild vision impairment. Prevention through genetic testing before breeding is the only way to stop CMR1 from being passed to future generations.
Is it safe to breed a CMR1 carrier?
Yes, carriers can be bred safely to a clear (N/N) partner. This pairing produces 50% clear and 50% carrier puppies — none affected. Never breed two carriers together, as that produces a 25% chance of CMR1/CMR1 puppies who will develop retinal lesions.
How do I test my Frenchie for CMR1?
CMR1 testing is included in comprehensive DNA health panels from Embark, Animal Genetics, and DDC. Order a full French Bulldog health panel that covers all four major genes: DM, HUU, JHC, and CMR1. Results return in 2 to 4 weeks.