There are several changes that are associated with the aging process in all mammals. One of these hallmarks of the aging process occurs in the lens of the eyes which will turn from a clear to a white color. In most cases this is a slow process that begins in the cat and dog around ten years of age. It would be rare however to go blind from this normal change before the pet dies of another cause.
The lens is located in the center of the eye and normally contains no water as this would bend (refract) the light rays as they enter and thereby distort the image to the back of the eye. In order to keep the water that surrounds the lens from penetrating it there is a tight capsule that protects it. This capsule is what breaks down with age and allows water and thus light to be refracted back so you begin to see a cloudy appearance to the lenses. The doctor word for this is nuclear sclerosis and should not be confused with the pathological condition called cataracts. If you are unsure if your pet has nuclear sclerosis or not, take a flashlight and shine it into the center of one eye.
If you do not see any cloudy white spot in the center of the lens then your pet probably does not have any nuclear sclerosis present. If you are still unsure ask us the next time you are in for an annual check-up.