A cataract is an opacity (or whitening) of the lens of the eye and may be due to old age, genetics, or diabetes. Cataracts are the major cause of blindness in dogs. Surgery is performed to remove the cataract from the lens (the same procedure as human cataract surgery). In some cases an artificial lens is implanted after the cataract has been removed. A lens injector is used to place the lens underneath the cornea and on top of the lens capsule. Placing a lens allows the patient to be able to see both near and far. Without the lens it is a bit difficult to see objects in close proximity.