The Tibetan is a very hardy breed and is considered long-lived with most living well beyond 12 years and many to 15 or 16 years. Some problems found in the Tibetan Terrier are: hip dysplasia (HD), patella luxation (PL), progressive retinal atrophy (PRA), lens luxation (LL), hypo-thyroidism, cataracts and canine neuronal ceroid lipofuscinosis (CCL/NCL). Some of these problems have been proven to be hereditary, and conscientious breeders have screened their stock and can explain these problems and their incidence. Many breeders will have knowledge of their puppies’ bloodlines and potential buyers are advised to ask questions and inquire as to evidence of any testing done on the sire and dam.

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Progressive retinal atrophy (PRA) is the name given to a group of hereditary retinal diseases in dogs. Although there are several classifications of the disease according to the age of onset of the disease and the types of retinal pathology which occur, almost all forms of PRA eventually lead to complete blindness.

The first sign of most types of PRA is night blindness. This is because the rods (the cells which allow vision in reduced light) degenerate before the cones (the cells which allow vision in the bright light). Often dogs will bump into objects in a dimly lighted room; a room in which a person can see well enough to avoid the object. Gradually dogs with PRA will lose their ability to see in lighted rooms and will go completely blind. They will frequently have dilated pupils. Sometimes owners will notice increased shininess or hyperreflectivity to the back of the eye.

Veterinary ophthalmologists who examine dogs with PRA will see a decrease in the size and number of the retinal blood vessels and a change in the reflectivity of the tapetum (the shinny membrane behind the retina). An important test done by ophthalmologists to diagnose PRA is an electroretinogram (ERG). This test detects the small electrical signals given off by the cells of the retina when they respond to light. The ERG is done by placing a contact lens on the eye and 2 small electrodes on the head. A bright light is then flashed into the eye. If the retina is normal, a distinctive signal is given off by the retina which is amplified and measured on a computer. If the retina is abnormal, the signal will be reduced in amplitude.

In all breeds except Siberian Huskies, PRA is inherited by an autosomal recessive gene. Fortunately, Drs. Gustavo Aguirre and Gregory Acland at the James A. Baker Institute at Cornell University have localized the gene for prcd in some breeds of dogs to chromosome 9. This has led to the development of a blood test for PRA. The ability to identify carriers of the gene for PRA by a blood test will be a tremendous aid to dog breeders.

source: CERF

A list of the PRA/LL affected, diganosed Tibetan Terriers can be found on the Tibetan Terrier International site.