Cataract

A cataract is when the lens of the eye gets cloudy. It is a treatable medical condition. Cataracts can cause short-sightedness (myopia), which means you cannot see things in the distance but can see things up close.

A cataract in a human eye

If not fixed by surgery, some types of cataracts will cause blindness (which means you cannot see anything at all). In a simple operation, the old lens can be replaced by a new plastic one. Many thousands of people have had this operation.