At what age do Lhasas show the first signs of PRA? With only 15 cases of PRA found so far, we do not have enough information specifically for Lhasas. We can only go by the information from other breeds. The closest breed is the Tibetan Spaniel. These develop PRA between the ages of 2 and 4. If they show no signs of the disease by 5 years, it is highly unlikely they ever will*.
*Scientific reference: http://mendel.berkeley.edu/dogs/diseases/pra/pramenu.html

If the disease does not show up until late, animals will be used for breeding which later prove to have PRA. How can the spread of PRA be stopped? In a late onset disease, unless electroretinography is done, it is impossible to guarantee that an animal is not homozygous for the defect until the animal is about age 5or 6. To be certain that affected dogs and their carrier children are not used for breeding, animals testing clear at a younger age, might be bred, but then their get should not be bred until the parents are proven to be free of disease at 5 or 6. This is the only way to weed out a significant number of carriers, and effectively prevent the spread of the gene.

What is electroretinography? This is an electrical measurement of retinal function. It consists of recording the brain wave response to light flashed in the anesthetized dog's eyes. Accurate recording of the ERG requires that the dog be anesthetized. In all dogs showing clinical evidence of PRA, the ERG response is severely diminished or absent.

Diagnosis of PRA is normally made by ophthalmoscopic examination. This is done using an indirect ophthalmoscope, and requires dilatation of the dog's pupil. All forms of PRA have the same sequence of changes: increased reflectivity (shininess) of the fundus (the inside of the back of the eye); reduction in the diameter and branching pattern of the retina's blood vessels; and shrinking of the optic nerve head (the nerve connecting the retina to the brain). These changes occur in all forms of PRA, but at different times in the different breed-specific forms. Usually by the time the affected dog has these changes there is already significant loss of vision.

The ERG can also be used for early diagnosis of specific forms of PRA,  to detect PRA-affected dogs before changes can be seen with the ophthalmoscope. For example, a Tibetan Terrier was diagnosed with PRA by ERG at 6 months. Not until the dog was 18 months was anything seen using the ophthalmoscope. Interpretation of ERG results requires very carefully controlled ERG recording conditions, and a thorough understanding of the age of onset and rate of progress of ERG changes expected in that specific form of PRA.

People are very concerned about their reputations. How can we convince them to cooperate? I think it is most important for people not to turn this into a witch hunt. In a competitive situation like dog breeding, some degree of this is inevitable. But I think the trick is to get ahead of the gossip. If you test, and confess (if you have it), you prove to everyone that you are a serious breeder, and are trustworthy. Once most people see that the sky does not fall on a candid breeder, they are more inclined to do the same. But it does take some courage to be the first.

Should ALL our dogs be tested? It would be desirable, from an epidemiologic standpoint, to examine every dog. However that would not be an efficient public health measure. The most important factor is identification of affected animals which will be or have been bred. That is why ALL possible Lhasas, two years and older, that have been or will be bred, should be tested. In a year or two we should have a DNA test for PRA. This will enable the breeder to take a swab, and send it to a laboratory, and get a result which will tell if the defective gene is present, and whether the animal carries one or two copies. This can be done on newborn pups, so very early selection from litters will be possible.

What about the expense of testing our dogs? Clinics can be arranged at club meetings or dog shows. The equipment needed is portable, the test is quite brief, and most Vet. Ophthalmologists wouldn't turn down the opportunity to make $20 per dog if a sufficient number of dogs were guaranteed to turn up. - Especially if he/she got a little free publicity from contributing a little time to a good cause.

Should all possible carriers be prevented from breeding? In small, or isolated, inbred populations, it may not be desirable to try to remove all the carriers. The reason for this is that these populations may be suffering from too limited a gene pool to permit more drastic pruning. In these cases, outcrossing may be a preferable course. Nature selects against the affected animal. The carrier is perfectly healthy. Our present methods of detecting affected and carrier animals are crude. Eugenic measures based on these methods will be minimally successful, and if carried to extreme, may be wasteful of perfectly normal animals, and the healthy genes they carry. Nevertheless, I think the choice is eye exams before breeding, particularly using the lines that have known carriers, or hold off breeding until a genetic test is available.

If that is true, what use is testing using eye exams for PRA now?Why not wait until there is a DNA test? When the breeding population has been tested, we will then know the dimensions of the problem, and what remedies to apply. Without testing, breeders are stumbling in the dark with an unknown number of landmines. With the DNA test, we will have the tool to remove the mines altogether. But until then, isn't it is better to know where the mines are planted?

What are some practical steps we can take now to control PRA?
1. The most important factor is identification of affected animals which will be or have been bred. That is why ALL Lhasas, two years and older, that have been or will be bred, should be tested.

2. Avoid using animals that carry the gene. Using older dogs, proven free of PRA will always be a wise choice, and 2 years seems to be a good age to begin using a bitch. Puppies can be sold under contract to wait until the bitch is proven free of disease, or as pets with spay/neuter contracts.

3. Outcrossing to unrelated lines will lessen the probability of homozygosity. Until we have a DNA test, it might be prudent to avoid doubling up on any dogs in our pedigrees. Breeding by phenotype rather than by pedigree offers the advantage of doubling on the selected characteristics, but not on other unknown characteristics.

4. If there is no pressing need to breed, delay breeding until we have a DNA test. The ETA of this test is reportedly less than 2 years from now.