Have you ever noticed a cloudiness in the eyes of your older pet? A foggy appearance that occurs, not on the surface of the eye, but deeper within the internal structures? Your first thought may be that your pet has developed cataracts, but a cloudy eye can also signal another condition called lenticular sclerosis. To better understand the difference between the two conditions, we should first look at what the lens of the eye actually is.

The lens

The lens sits behind the iris (the colored part of the eye) and is a clear oval-shaped structure that helps the eye to focus on an object. In order to see well the lens must be absolutely clear. Any cloudiness to the lens is akin to having to look through a dirty pair of glasses. If the cloudiness is severe enough, to the point of opacity, then blindness occurs. So what causes that cloudiness you may see in your dog’s eyes? Most commonly it will be caused by either a cataract or a condition called lenticular sclerosis. Both of these will cause changes in the lens of the eye, but they stem from very different causes.

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Lenticular sclerosis

Lenticular sclerosis is a very common condition that occurs as a pet ages. It generally occurs in both eyes as the lens thickens with age. This causes a haziness of the lens that still allows transmission of light. Dogs and cats with lenticular sclerosis can still see, but their vision may not be as good as it once was. We do not treat this condition since it is a normal part of aging and it does not affect their vision significantly enough to warrant any treatment.


Cataracts are the other condition that can cause opacity of the lens. This condition is more complex than lenticular sclerosis because cataracts can have a variety of causes and can progress to blindness. Cataracts can occur in dogs of any age, and can have a genetic basis (inherited from their parents) or be secondary to another disease such as diabetes. Certain breeds such as Beagles, Golden Retrievers, and Yorkies have an increased risk for cataracts. Inherited cataracts are much more rare in cats than in dogs. Unlike lenticular sclerosis, which will not cause blindness, cataracts often will lead to a blind eye as they completely block the passage of light. They can also occur in one or both eyes.

Cataracts can be treated surgically in dogs, just like they are in people, and dogs that undergo cataract surgery can have their sight restored. Cataract surgery is rarely performed in cats.

If you notice any cloudiness of your pet’s eye it is time to get him or her to your veterinarian for a thorough eye exam, especially since Petplan offers coverage for veterinary exams related to illnesses and injuries.

Jul 18, 2012
Pet Health

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