On their evening walks, he seems a bit more hesitant when he approaches sidewalk curbs and occasionally will run into objects. The impact is not full-bore; instead, he sort of bumps the object. Miranda likens it akin to him feeling for something.

The 9-year-old cocker spaniel has been in good health, except for a few ear infections.

When Miranda started to notice the change in Freddie about four months ago, she began paying attention to his eyes. At first, she noticed nothing abnormal, but now she perceives a color change, a sort of bluish-gray to his eyes. She is concerned that he might have cataracts.

Changes to sight are natural, especially with aging. Humans go through the same process. But decreasing eyesight can be difficult to spot in pets, especially if there is a gradual onset. Dogs have powerful senses of smell and hearing and, as a result, are able to compensate for decreasing sight. Even when totally blind, dogs are adept at negotiating their environment.

When grossly assessing a dog's eyesight, I place several objects on the floor of a small room and allow the dog to walk through and around them. If there is no sign of compromised eyesight, I repeat the test with the objects in a different pattern with lower light conditions. If there is less success with this step, I can then assume some compromise of site in lower light conditions. This is most compatible with lenticular sclerosis, which involves a decrease in clarity of the lens within the eye. This process is usually a normal occurrence with aging and it does affect eyesight. This is especially apparent in lower light situations as the lens does not pass light through to the back of the eye, the retina, as well as it would if it were clear.

This condition can occur at younger ages and is considered to be progressive, although there are many dogs that have this condition and do not eventually go blind.

Lenticular sclerosis is often mistaken for cataracts, which are a more focal change within the lens. Cataracts occur as a crystallizing process that blocks light transmission through the lens. They can be progressive and often lead to blindness. Cataracts are commonly seen with patients that have diabetes.

Freddie needs to be evaluated to determine the cause in his ability to see. Lenticular sclerosis is not a process that is generally treatable; however, if cataracts are involved, there are good options for treatment.

Cataracts, even when diabetes is the underlying cause, are curable.

The cure involves surgical removal of the lens, which can then be followed by insertion of a new lens to restore vision.

An important pre-operative evaluation of these patients needs to include vision assessment. There are cases where a patient is blind or has greatly compromised vision caused by other changes associated with the eye along with cataracts. Removal of the cataracts will not restore vision to these patients.

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(Jeff Kahler is a veterinarian in Modesto, Calif. Questions can be submitted to Your Pet in care of LifeStyles, The Modesto Bee, P.O. Box 5256, Modesto CA 95352.)