Common vision problems in aging dogs are nuclear sclerosis and cataracts. If the center of your dog's eye lens appears hazy or gray, he has nuclear sclerosis — a normal part of the eye's aging process. Nuclear sclerosis is caused by the formation of new fibers at the edge of the lens. These fibers push inward toward the center. Nuclear sclerosis isn't painful and it won't greatly affect your dog's vision, although he may have a little trouble focusing on objects close-up.
Cataracts can sometimes be removed surgically, but if that's not possible, you can help your dog navigate his surroundings by scenting furniture and other objects at his nose level. Be sure to test an inconspicuous area first to make sure that the perfume or other scent you use doesn't harm the finish.
Acquired cataracts — as opposed to juvenile cataracts, which are congenital or hereditary — are generally a consequence of aging or a side effect of diabetes. Cataracts cause the lens to become opaque, starting at the center of the lens and spreading outward, gradually decreasing the vision. Fortunately, dogs that are blind or have limited vision can get around quite well using their senses of smell and hearing. You can also learn to communicate with them using a whistle. Consult a trainer for advice on how to do this.