A cataract is a clouding of the clear lens in the eye and is one of the leading causes of vision impairment. While cataracts most commonly occur in those who are older, they can develop in younger people, including congenital cataracts at birth. Cataracts occur as part of the ageing process but harmful UV exposure, smoking, and diabetes can contribute too. Surgical removal of the cataracts with an implant of an intra-ocular lens restores sight.