MRD
Multifocal Retinal Dysplasia
Testing method
Ophthalmoscopic examination of the retina following pupil dilation, using indirect ophthalmoscopy. Most reliably performed in puppies between 6 and 12 weeks of age as part of litter screening. Important note: once a dog has been recorded as clinically affected for MRD, it remains clinically affected for life — even if signs are not detectable at a subsequent examination due to remodelling of the retinal tissue.
What is multifocal retinal dysplasia?
Retinal dysplasia is a failure of normal retinal development. In multifocal retinal dysplasia (MRD), the neurosensory retina develops abnormally, resulting in characteristic folds, streaks, and rosettes visible on ophthalmoscopic examination. The condition is congenital — it is present from birth — and in most affected dogs it is non-progressive.
The ophthalmoscopic appearance ranges from small grey linear streaks or vermiform folds in the tapetal fundus to round or Y-shaped lesions. In most cases these are located in the area of the tapetal fundus dorsal to the optic disc, though they can occur elsewhere. A more severe variant, geographic retinal dysplasia, involves a circular pattern of folds with a central area of possible flat retinal detachment, and tends to be unilateral.
An important point about MRD results
Once a dog has been examined and recorded as clinically affected for MRD on a BVA certificate, it remains clinically affected for life. This is because the genetic predisposition does not change, even though the ophthalmoscopic appearance may become less obvious with age as the abnormal retinal tissue remodels and thins. If a dog's previous MRD affected status is known and the signs are not detectable at a subsequent examination, the panellist will score through both boxes and add a comment to the certificate explaining why.
This means it is essential to inform the panellist of any previous MRD affected result before an examination begins.
Breeds affected
MRD is certified under the BVA scheme in the Cavalier King Charles Spaniel, Hungarian Puli, Golden Retriever, Labrador Retriever, Rottweiler, American Cocker Spaniel, and English Springer Spaniel. Total retinal dysplasia — the most severe form — is separately certified in the Bedlington Terrier, Labrador Retriever, Samoyed, and Sealyham Terrier.
Litter screening
MRD is a congenital condition and is most reliably detected in puppies between 5 and 12 weeks of age. This is why litter screening is the primary testing route for the affected breeds. All puppies in a litter are examined at the same session, and all must be microchipped before the examination.
The optimal window for litter screening is between 6 and 12 weeks. Examination before 5 weeks is not recommended as the retina is still developing. After 12 weeks, litter screening certificates cannot be issued under the scheme.
For breeds where MRD can also be detected in adult dogs — particularly the geographic form — routine annual examination of breeding stock is also recommended in addition to litter screening.
What the examination involves
The examination is performed following pupil dilation with tropicamide drops. The panellist uses indirect ophthalmoscopy to examine the retina, paying particular attention to the tapetal area dorsal to the optic disc and the peripapillary region. The examination is non-invasive and well tolerated by puppies.
Litter screening is available at all our regular clinic dates. Please mention at the time of booking that you are bringing a litter, and let us know how many puppies you are bringing so that enough time can be allocated. The first puppy is examined at the standard BVA litter screening fee; additional puppies are charged at the BVA additional puppy rate, invoiced on the day.