Juvenile Cataracts and Siberian Huskies
Juvenile or hereditary cataracts are a cloudiness of the lens of the eye that appear at a young age, usually as a puppy or young adult. The other types of cataracts that form in the dog are congenital (present at birth) and senile (common in dogs over 8 years of age due to the aging process). Rarely a cataract can be caused by environmental factors such as trauma, radiation, toxins, or disease. In the Siberian Husky, hereditary cataracts begin in the posterior axial cortex at approximately 6 months to 12 months of age. However, there are Siberians that develop cataracts earlier and later than this age range. The cataracts may be present in either one eye or both eyes and occur at different times. The lens focuses the rays of light in order for an image to occur on the retina. If a cataract develops, the light rays entering the eye are decreased and sight can be diminished. Cataracts may affect just a local portion of the lens or involve the entire structure. Progression of the cataract in the Siberian is variable and sight may be mildly diminished or the cataract may rapidly progress and contribute to glaucoma or rarely blindness.
In order to decrease and eliminate hereditary cataracts in this breed, all breeding animals need to have their eyes examined by a veterinary ophthalmologist whom is a member of the American College of Veterinary Ophthalmologists (ACVO). The eye examination will not only detect cataracts, but other diseases affecting the breed such as corneal dystrophy. This eye exam is completely yearly for all breeding dogs and the results are given to the owners by the ophthalmologist. If the eyes are normal, the dog can be entered into the CERF (Canine Eye Registry Foundation) or SHOR (Siberian Husky Ophthalmologic Registry) program. Dogs are entered into the registries after one year of age and the registry information is updated at each eye examination. All buyers of Siberian puppies should insist on seeing the eye registry papers or eye examination results of both parents. This eye examination should be current and completed within one year of the breeding. If the breeder cannot supply the proper documentation, look elsewhere for a puppy. Juvenile cataracts cannot be underestimated in this breed.
The CERF eye reports of all Siberian Huskies examined from 1991 – 1999 show an incidence of 10.95% hereditary cataracts in dogs examined. Corneal dystrophy, another type of eye disorder, was seen in 3.85% of Siberians examined.
Research is now being conducted into studying the genetic mode of transmission of hereditary cataracts and the location of the affected genes on the DNA strand. The hope for the future is the development of a DNA test to determine if a puppy is a carrier, affected, or clear of cataracts at 8 weeks of age.
PRA (Progressive Retinal Atrophy) In The Siberian Husky PRA is a degenerative disease of the retinal visual cells which may progress to blindness. It may be detected by an electroretinogram (which is not part of a routine eye exam.) before it shows up clinically. AVCO statistics from 1991 – 1999 show a incidence of 0.17% with 16 affected dogs In addition, 34 dogs were screened as suspicious for this disease and that percentage is 0.30%. So it is a disease that needs to be monitored. For an article about the specifics of PRA transmission in Siberians and Samoyeds and access to the genetic test to find the marker, please visit the Optigen web site.