A cataract is a loss of normal transparency of the lens. Any opaque spot on the lens, regardless of its size, is technically a cataract. The lens is a normally transparent structure that focuses images upon the retina.
A cataract that is visible to the naked eye appears as a milky gray film behind the pupil.
The majority of cataracts in dogs are genetically determined, but the mode of inheritance varies among breeds. Congenital cataracts (also known as Juvenile Cataracts) have been described in more than 75 breeds including:
- Cocker Spaniels
- Bichon Frise
- Boston Terriers
- Wire Fox Terrier
- West Highland White Terrier
- Miniature Schnauzer
- Standard Poodle
- Siberian Husky
- Golden Retriever
- Old English Sheepdog
- Labrador Retriever
Acquired cataracts occur as a consequence of aging and other eye diseases, most notably uveitis. Dogs with diabetes can develop cataracts in a matter of weeks. Puppies fed milk replacement formula that is deficient in arginine can develop bilateral cataracts. Newer formulas have been adjusted for this problem.
A genetic test for some of the affected breeds is under development through VetGen.
Senile cataracts should be distinguished from nuclear sclerosis, a normal aging of the lens in which new fibers are continually forming at the periphery of the lens and pushing inward toward the center. These changes cause a bluish haze in the lenses of older dogs. This haze does not interfere with vision.
Senile cataracts do not need to be treated unless both eyes are involved and the degree of blindness is such that the dog is having difficulty getting around. Visual impairment can be corrected by surgery - removing the lens, either by extraction or preferably by an operation called phacoemulsification. This involves fragmenting the lens with ultrasonic vibrations and then replacing it with a clear plastic intraocular lens. Without a lens, the image the dog sees is blurred and the edges are indistinct, but objects can be seen.
Some juvenile cataracts will be spontaneously re-absorbed, usually within 1 year of their appearance. Complete resorption results in vision comparable to that of a successful lens surgery. If the cataract is breaking down on its own, as in resorption, surgery should not be done.
Hereditary cataracts can be prevented by not breeding affected dogs and those who carry the gene. Dogs with congenital cataracts can be identified by annual eye examinations carried out by veterinary ophthalmologists affiliated with the Canine Eye Registry Foundation.
Please contact your veterinarian with questions regarding this condition.
Show Sources & Contributors +
Publisher: BowTie Press, 2005
Authors: Kristin Meuh-Roe, Jarelle S. Stein
Dog Owners Home Veterinary Handbook
Publisher: Wiley Publishing, 2007
Authors: Debra M. Eldredge, Liisa D. Carlson, Delbert G. Carlson, James M. Giffen MD