But a product's SPF indicates only its ability to defend against sunburn-causing ultraviolet-B rays and not against ultraviolet-A, which penetrate deeper into the skin and cause premature aging. (Both types contribute to skin cancer.) For example, a person wearing SPF 50 could spend considerable time in the sun without getting burned.

WSJ: The Myths of Daily Sunscreen

In it, he uses eye drops made of a special riboflavin (a type of vitamin B) formulation and a very weak ultraviolet light to strengthen the collagen fibers in the eye.

FORBES: A New Hope for Those With Down Syndrome...And a Rare Eye Disease