Cataract is the clouding of the lens in the eyes. The eye's lens is usually clear and helps focus light rays onto the retina. It is composed of proteins that are normally arranged clearly and organised. However, in cataracts, these proteins start to break down and clump together, causing the lens to become cloudy. This cloudiness prevents light from passing through the lens properly, leading to blurry or impaired vision.

This fact sheet is part of our Ophthalmology and Optometry Information Guide series, developed to help people understand eye conditions and their impact on navigating the built environment.