The lens is a soft, transparent tissue that sits behind the iris. It helps focus incoming light onto the retina. Common disorders of the lens include those that affect its transparency (such as cataracts), and those that affect the placement of the lens.
A cataract occurs when the lens becomes cloudy or opaque, which effectively blocks light from reaching the retina. This causes a loss of eyesight that can range from mild vision problems to partial blindness. In contrast to dogs, most of the cataracts that develop in cats do not occur on their own or because of an inherited predisposition. Instead, they often occur as the result of trauma or inflammation of the anterior uvea (see Eye Disorders of Cats: Inflammation of the Anterior Uvea).
In general, treatment for cataracts involves surgery to remove the affected lens or lenses. Advances have been made in this procedure, but complications are possible. In animals in which cataract surgery is not performed, continued monitoring is very important. Follow your veterinarian's recommendations for treatment of cataracts.
Lens displacement can occur in cats. The displacement may be due to trauma, longterm inflammation of the uvea, or glaucoma. Lens displacement also occurs in elderly cats. The only effective treatment is surgical removal of the lens (see Eye Disorders of Dogs: Disorders of the Lens in Dogs).
Last full review/revision July 2011 by Kirk N. Gelatt, VMD, DACVO; David G. Baker, DVM, MS, PhD, DACLAM; A. K. Eugster, DVM, PhD