Arcus senilis is a gray or white arc visible above and below the outer part of the cornea — the clear, dome-like covering over the front of the eye. Eventually, the arc may become a complete ring around the colored portion (iris) of your eye.
Arcus senilis is common in older adults. It's caused by fat (lipid) deposits deep in the edge of the cornea. It isn't related to high cholesterol, however. Arcus senilis doesn't affect vision, nor does it require treatment.
An arc or ring around the iris sometimes occurs in younger people who have severe cases of high cholesterol and high triglycerides passed down through families (familial hyperlipidemia). In people with familial hyperlipidemia, this typically occurs before age 45.