the retina seen through the ophthalmoscopic instruments
| Papillon and phalènes unfortunately suffer
from a hereditary eye-disease called PRA - progressive retina atrophy - this is a
hereditary eye-defect found in a lot of different breeds. Even among wild living wolfs PRA has been found. The disease develops slowly causing the retina, the light sensitive tissue in the back of the eye to degenerate and die. The affected dog slowly looses eyesight in the dark, and usually end up blind!! In Papillons, however PRA develops extremely slow, and in such a way, so the dog often will NOT become completely blind - even at high age. But the sight will start to deteriorate in a relativety young age, and a dog with a bad eyesight is not worth much in Agility or obidience..... Nevertheless, it is an unwanted defect in the breed, and breeders must make every effort, not to spread the gene by breeding dogs who are known to be genecarriers or are affected by PRA. The gene is
recessive and only if a dog gets a gene from EACH parent, it will develop PRA. PRA in papillons are a late onset form. The first signs can usually been seen by opthalmoligisk examination at the age of 3-4 years, but they often are overlooked because the initial stages are so very-very faint. The bloodvessels are thinning and deteriorating. Later on a mirrorlike reflex are seen from the retina. Sometimes the owner will notice the dog to have some reluctance against going out in a dark yard, climbing stairs or generally moving around strange places in the dusk. But very often there are nothing at all, which makes anyone suspect problems with the dog's sight. |
the retina seen through the ophthalmoscopic instruments |
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| Fig. 1. The normal retina. Note the many prominent blood vessels. | Fig. 2. A mid-stage PRA retina. Notice how the vascularity has been markedly reduced. |
Thanks to NetPets for the pictures above.
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We have discovered a special opaque-grey-grenish shimmer from the affected dogs eyes when exposed to flashlight. This opaque shimmer is well described in veterinarian notes about PRA. |
| The dog at the top is diagnosed PRA by ERG
as 1½ year The 2 in the middle are both ERG-cleared, the one to the left is 2 years, the one to the right is 7, and the one below is opthalmological cleared at 5 years.
Notice the different colouring of the eyes. The PRA-eyes
are sort of opaque, bottomless, the flashlight are being reflected completely by the
degenerated retina. The others are bright yellow to greenish, with no halo around. The
pupils are well defined, and not as wide opend as in the PRA-dog. We just placed the dog at a table in the evening when the pupils were naturally dilated, and then shot some pictures using the flash - without the anti-red-eye-function - of course !! |
The history:
| Some rumours are saying PRA was
"invented" in Sweden. This is NOT true. The gene-defect is not national, it is breed-specific!! There have been diagnosed PRA in dogs bred in UK, USA, Norway, Holland, Iceland, Sweden and Denmark, but of course most PRA-cases are found in those countries, who thoroughly test their dogs. In Denmark and Sweden the breeders can't get their puppies’ registrated unless both parents have been tested clear of PRA within the last 12-month before mating. If a dog is diagnosed PRA, then it will be excluded from breeding as well as it's parents and offspring. Back in '92 Pia Johansen, Gold Wings, started gathering
eye-test-results. Hoping to map the gene in order to prevent breeding dogs who were
carrying the gene. |
| Due to this enormous database, we are able
to calculate, by use of Hardy-Weinbergs Law, how many carriers there actually are in the
breed. The discouraging result is close to 40 % |
To do ....
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As almost every papillon used
for breeding, are bred before the above-mentioned diagnosable age, the problems are
obvious. And having the frightening high carrier numbers in mind, looking for carriers in
a pedigree in order to avoid them in ones breeding program makes very little sense. Actually to only sensible way to minimise the incidence of PRA, is to make sure NOT to breed affected dogs......How?? One way is to wait breeding before the dog is at least 3½ or older, the longer you wait the higher the certainty for the diagnose to hold. Another possibility is testing by ERG, a testmethod which for sure, at an age of 2 year, can give a very high validity of the diagnose - quite near 99 %. The testmethods today are normal opthalmoscopy and ERG. By ERG the dog has to be anaesthetised. Then a special
contact lens are placed on the eye, and the eye are exposed to various light sources:
glimpses, red/blue and white. The eye/retina's responses to the light are recorded, and
afterwards these records are evaluated, preferably against a set of normal papillon
retina-curves. The diagnose is reliable at 95% at 2 year of age
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At
the moment we know only of ERG done in Norway, Sweden and by Gus Aguirre US to be trusted. Unfortnately we have seen dogs, tested by ERG in Denmark who were proven affected or suspected, to later turn out cleared by ERG done in Norway. Still, there are so far not found any ERG-cleared who later turned out affected ! Latest news !!! A dog, now 3 years of age, ERG-tested twice in Denmark, both times suspective for PRA, a third ERG in Norway was marked "the dog must be re-tested by opthalomogy - the curves are somewhat low, but within the normal" (usually the Norwegian as well as the Swedish ERG are valid for life !!!) Another dog, a female Chatoy's Crown
Wictoria, The ERG-test is subject for further investigations - proff. Gus Aguirre worked with English Cocker Spaniels, Please read the story here. |
The future...
| At the moment there are no way to test
whether a dog is genecarrier or not. But in Denmark we have collected a lot of bloodsampels from familygroups suffering from PRA. These samples have been send to proff. Gus Aguirre at Cornell University, USA, who are researching in finding the causative gen. In time only a single bloodtest is needed to determine whether a dog is genetically free, carrier or will develop PRA. As mentioned in the ECS-story - what we think we know today, may not at all be the whole truth, but remember: We are part of the future made today... |
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your contribution.....
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Please participate in making the "LIST" as complete as possible, in order to help the breeders. Please send a copy of your dogs certificate together with a copy of the pedigree to: |
Lene Kiilerich |
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Due to abuse and unauthorized copying, the eye-list will no longer be available to others than those serious breeders who send their eye-certificates to be included. We find it unacceptable, that people who clearly do not want to contribute in the completion of the list, otherwise like to benefit from people who do. At the same time we would like to stress, that the list's send out before ½ a year ago no longer are valid - MANY dogs have chaged diagnose - both from affected to cleared and vise versa - so please do not use older lists as reference for future discussions. |
It is of course very sad that we have to take this step, but we will always provide information on certain dogs on request. If you send in your dogs eye-papers - you are entitled to receive information about certain dogs on request for 1 year from the date we receive the papers - and so on. |
If you have any questions about PRA,
please ask.
last update 27-05-02
created and maintained by Pia Johansen
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