Nuclear sclerosis is a normal aging change of the lens. The lens is made up of layers of cells arranged somewhat like the layers of an onion. As animals get older, the cells become packed together more tightly as new layers are added. The increased density of the lens causes it to look cloudy in dogs over about 7 years of age. The lens will continue to appear cloudier over time. Nuclear Sclerosis is easily mistaken as a Cataract, which is a different problem that also causes the lens to become cloudy. While a cataract is an abnormality that can cause blindness and inflammation inside the eye, nuclear sclerosis is normal for an older dog, and the condition has minimal effect on vision. Just as for middle-aged people who need reading glasses, a dog with nuclear sclerosis will not be able to see well up close. Going down stairs and catching a small treat may be more difficult.
Another normal aging change occurs in the retina where the cell layers responsible for night vision become thinner. This is also a slowly progressive change. You may notice that your dog hesitates when going outside at night. It may be helpful to turn on more lights. This normal aging change must be distinguished from Progressive Retinal Degeneration which is an inherited condition that results in blindness.
Some older dogs will develop a weakness in the muscle in the iris that constricts the pupil. These dogs may be light sensitive. If their lens is also cloudy, this may be more noticeable through their larger pupil, increasing the cloudy appearance of the eye.
Both of these changes are normal, very slowly progressive and should never cause significant problems. If you notice a major change in your dog’s vision, please give us a call.
For even more information, here is a brochure on age-related eye conditions provided by the American College of Veterinary Ophthalmologists.