The lens is a transparent structure that lets light into the eye. Cataracts are cloudy areas that form in the lens. Cataracts are the leading cause of vision loss in people over the age of 40, but cataract surgery is a routine operation nowadays and the most common kind of eye surgery.

The number of cataracts is increasing with the aging population. In the United States in 2010, there were 20.48 million cases, rising to 24.41 million in 2015. By 2050, nearly 50 million Americans are expected to have cataracts.

A cataract causes a part of the lens to becomes opaque, or cloudy. Light does not pass through easily, and vision becomes blurry, like looking through a fogged-up window. The cloudier the lens, the worse the vision will be.

Congenital cataracts may be present at birth or appear shortly after, or at some time during infancy or childhood.

Age-related cataracts appear later in life and are the most common type. This article will focus on age-related cataracts.