I wonder if anyone can tell me whether a diagnosis of Cone-Rod Dysplasia in a 10 month old pup would be less reliable if the dog is a blue merle. In other words could it be a mistake or is it as reliable to diagnose as in any other colour dog.

Thanks

Fiona

Yes is the short answer but there is a far longer answer which I don’t have time tonight to go into but very briefly, there is reason to believe that at the very least in some cases, CPRA is NOT a hereditary defect but is caused by a defect in the metabolism pathway of vitamin E. It would be interesting for you to get your dogs eyes tested by Prof. Peter Bedford as it was his team which made the breakthrough.

Sorry this is a bit short, John

Thanks for your quick reply John

Fiona

Now I have a little more time, the info I passed on yesterday was contained in a Technical Review issued by the Guide Dogs for the Blind. Professor Peter Bedford holds the GDBA chair of Canine Medicine and Surgery at the RVC University of London and the research was funded by the Guide Dogs. They released the paper in June 1999.

CPRA is a disease of the outermost layer of the retina and through this, the degeneration of the rods and cones. As such the degeneration is a secondary effect, not primary effect. Correctly, today CPRA is known as RPED, (Retinal Pigment Epithelial Dystrophy). With this disease the onset can be as young as 15 months or as old as 8 years and is totally independent of breed!

Most of the research was done with Labradors, Golden Retrievers, Cocker Spaniels and Hungarian Puli and Briards and it was found that the degeneration could be arrested by supplementing vitamin E in the diet!

I see you are in Essex so you are not that far from the veterinary college at Potters Bar so it could be worth your wile seeing your vet and getting a referral to the ophthalmology department for a complete diagnosis and advice.

Regards John

Thanks again John for the information. Unfortunately, the puppy I am referring to now lives in the USA, but I will pass the info on, especially the part about supplementing with vitamin E.

Regards

Fiona

Hi John

The original question was about the blue merle pattern. Are you saying there is or isn't a connection?

Julie

The original question said:-

<<In other words could it be a mistake or is it as reliable to diagnose as in any other colour dog>>

In the eye testing which I am co-organiser of we have over 100 dogs a year attend the three sessions we organise and this is only us. Add that to all the other sessions held in other areas, by breed societies, game fairs and in veterinary surgeries and you can appreciate that totals up to an awful lot of dogs! Now I would never say that mistakes never happen but it is very rare. I would stress that this is using BVA/ISDS/KC ophthalmic panellists. These people are all highly skilled specialists.

However much I trust my vet and I have been with them for over 45 years I would never ask them to test my dog’s eyes. They could give me a rough idea but just as in our eyes it is the job for a specialist. Let’s face it, if you had an eye problem you would visit an optician rather than a GP.

So, the answer is, an experienced canine ophthalmic vet would be able to distinguish between a good Blue Merle eye and one with a problem. An ordinary Vet, who is in effect a General Practisioner and has to treat everything from a mouse to an elephant quite possibly could not.

Regards, John