Q: Can a vet determine the percentage of vision still present in a dog 10 years old with cataracts?
A: A veterinary ophthalmologist can make a very accurate determination of percent of vision remaining in a dog with cataracts. Most dogs with cataracts, which is a clouding of the lens, get them as part of another disease such as diabetes. Older dogs will get a normal clouding of the lens related to aging known as lenticular sclerosis. This is a mild change that usually does not affect vision.
Using a sophisticated array of instruments, similar to what is used in humans, an ophthalmologist can study the eye in detail and measure the amount of light that appears to passing through to the retina.
Dog owners can also get a good idea of how much vision is remaining by doing some simple vision tests with their dog. First, take a piece of cotton and drop it in front of your dog. See if he tracks it all the way down. Repeat if necessary and cover one eye at a time to see if there is a difference.
Then try turning off the lights in an unfamiliar room, and see how well your dog navigates the room. Dogs have excellent night vision, and should not have any trouble getting around in the dark. If your dog starts to bump into things, their cataracts are significantly affecting their vision. Of course, if you put them in an unfamiliar room and they bump into things when it is lit they are becoming or are already blind.
Dogs are excellent at memorizing their surroundings and many dog owners are not aware for up to several years that their dogs are actually going blind until they start running into things in an unfamiliar setting.
The treatment for cataracts is surgical removal, which has a high success rate when performed by a veterinary ophthalmologist. Not surprisingly, these procedures are not inexpensive.