Canine Multifocal Retinopathy

Canine Multifocal Retinopathy (CMR)

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What is Canine Multifocal Retinopathy?

 

Canine multifocal retinopathy (CMR) is an inherited condition affecting the retina, the light-sensitive layer at the back of the eye. It is characterised by the presence of multiple small areas of retinal elevation or detachment, often described as blister-like lesions.

 

These changes are usually identified during a specialist eye examination rather than through obvious signs at home.

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Cause and Inheritance

 

CMR is caused by a mutation in the BEST1 gene, which plays a role in maintaining normal retinal function.

 

• The condition is autosomal recessive

• Dogs must inherit two copies of the mutation to be affected

• Dogs with one copy are carriers and typically show no clinical signs

 

This makes DNA testing an essential tool in responsible breeding programmes.

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Clinical Signs

 

Affected dogs may show:

 

• Multiple small, round or irregular lesions on the retina

• Areas of retinal elevation (fluid-filled “blisters”)

• Changes visible on veterinary eye examination

 

In most cases, these changes are not visible without specialist equipment.

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Effect on Vision

 

Despite its appearance, CMR is generally considered a mild condition:

 

• Most dogs retain normal vision

• Some may experience slight visual impairment

• Blindness is extremely uncommon

 

Many dogs live completely normal, active lives without any noticeable impact.

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Development and Progression

 

CMR typically develops early in life:

 

• Usually identified in puppies from a few months of age

• The condition is often non-progressive or self-limiting

• In some cases, lesions may improve or resolve over time

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Diagnosis

 

CMR can be identified through:

 

• Specialist veterinary eye examination (ophthalmologist)

• DNA testing, which determines whether a dog is:

  • Clear

  • Carrier

  • Affected

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Management

 

There is:

 

• No treatment required in most cases

• No associated pain or discomfort

 

Management focuses on:

 

• Monitoring eye health

• Ensuring affected dogs live in a safe environment if vision is impacted (rare)

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Breeding Responsibility

 

As a recessive condition, CMR can be effectively controlled through careful breeding:

 

• Carrier dogs can be bred safely to clear dogs

• Carrier-to-carrier matings should be avoided

• DNA testing allows breeders to make informed, responsible decisions

 

At Womlu Mastiffs, we strongly support health testing and transparency to protect the future of the breed.

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Summary

 

Canine multifocal retinopathy is a recognised inherited eye condition in mastiffs, but in most cases it has minimal impact on quality of life. Through awareness, testing, and responsible breeding, its presence within the breed can be carefully managed.

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