Woof! asks prominent Mumbai vet, Dr. Vishwasrao (M.V.Sc., Ph.D. Surgery) a few questions on cataracts.
What is a cataract?
A cataract is any opacity in the lens of the eye. The normal lens is translucent (clear) and it transmits and focuses light onto the retina in the back of the eye. Cataracts cause varying levels of vision impairment and may lead to blindness. When a cataract is fully mature, no light passes from the eye to the retina (image-forming centre) and the dog is almost completely blind.
What causes cataract to form?
There are many causes of cataracts. The most common form of cataracts in the dog are genetic, inherited types.
Cataracts may also develop following trauma to the eye, in association with metabolic diseases such as diabetes, or may develop spontaneously in old age. Sometimes a puppy can be born with cataract (congenital cataract).
What happens to a dog that is blind?
A cataract can be unilateral (one eye) or bilateral (both eyes). If only one eye is afflicted, there isn’t much of a problem because the other eye accommodates and the dog will act and behave normally. The problem occurs when both eyes get afflicted.
Often, a pet owner may not realise his dog is blind and the actual onset of blindness may be difficult to pinpoint because a dog’s sense of smell will compensate for a decrease in vision. Animals that slowly lose their vision tend to memorise their surroundings. However, if the surroundings are altered the dog will start stumbling and get confused. This can lead an owner to deduce that the animal has gone blind suddenly. In actuality, the blind dog starts bumping into things only because the environment has changed.
A blind dog will also have problem recognising his owners because all he sees are shadows moving and at times the dog will also bark at the owner. It is only when the dog is close enough to smell the owner, will he recognise who it is.
What can be done to treat the cataract?
In human beings, drops are administered to mature the cataract as early as possible. The old lens is then removed and a new lens is implanted inside the eye. In India cataract surgery is yet in its infancy; the surgery involves the use of highly sophisticated and expensive equipment and certain expertise to carry out the operation. To the best of my knowledge there is no veterinarian trained for eye surgery in India nor do I know of anyone doing it on a routine basis.
How can cataract formation be prevented?
There is little you can do to prevent cataracts, especially if it is a genetic condition. However, if the cause of the cataract is known, it can be treated and the cataract can be delayed.
If your pet is diagnosed with inherited cataracts, there is not much one can do, however, you should notify the breeder so that no other litters are produced from the same sire and dam.
If your dog is diagnosed with diabetes, then maintain good control over the disease by monitoring blood and urine sugar as recommended by your veterinarian.