It is the clouding of the lens of the eyes. Due to this the patient may have a foggy vision, making simple activities difficult to perform. The cataract develops slowly and gradually s interferes with the vision.
The normal eye passes the light rays from the clear lens to the retina (light sensitive tissue) which sends chemical signals to the brain to read the image accurately. In cataract the lens will be cloudy and as a result the image on the retina will be blurry. Hence the vision may be affected and the image may not be correctly interpreted by the brain.