Genetic Defects of the Eye (continued..)
What is progressive retinal atrophy (PRA) & how is it transmitted?
Progressive retinal atrophy (PRA) affects the retina, the light-sensitive inner lining of the posterior part of the eyeball.
The retina contains two types of specialized cells called rods and cones. The rods are necessary for sight in dim light or night light,
and the cones are utilized in in bright light vision. The Siberian Husky has a unique type of PRA that is only found in Siberians and man.
This type of PRA is called XLPRA (X Linked PRA) since it is transmitted through the "XX" chromosome of the female. It will cause a loss of
night vision followed by a loss of day vision, eventually blindness. The recessive gene for XLPRA is situated on the "X" chromosome of the
female. Females who inherit a defective gene on the "X" chromosome from one parent and a normal gene on the other "X" chromosome from the
other parent, will not be seriously affected. They will be carriers with very subtle retinal defects and no loss of vision. The male puppy
from a carrier dam will receive either a defective gene or a normal gene, depending on what chromosome was copied in the DNA replication.
If he has the defective gene, the dog will be affected with PRA since males carry an "XY" chromosome. The disease in males can be devastating
with loss of vision as early as 5 months of age.
How are eye defects diagnosed?
Accurate diagnosis of eye defects requires the expertise of a board certified veterinary ophthalmologist who is equipped by knowledge
and training to distinguish hereditary eye diseases from non-hereditary eye disorders.
How prevalent are eye defects in the Siberian Husky?
Of the three major eye diseases of the Siberian Husky, hereditary cataracts are the most common, followed by corneal dystrophy,
and progressive retinal atrophy.
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