A person is said to have developed cataract when the eye lens becomes cloudy or opaque because of the formation of a membrane over the lens. This causes blurred vision and might eventually lead to complete loss of vision. Cataract is a medical condition that usually occurs in old age and cannot be corrected by any type of spectacle lenses. However, the vision of a person with cataract can be restored surgically by replacing the opaque lens in the eye with an artificial lens.