Cataract is the clouding of the eye's natural crystalline lens. It is the most common cause of vision loss in people over age 40 and is also the principal cause of blindness in the world. Development of cataract is mostly because of old age, but may be because of 'injury to eye', 'metabolic disorders like diabetes in body' or 'can be by birth'. Blurred or dim vision, difficulty in vision at night, sensitivity to light and glare, need for brighter light for reading and other activities, seeing "halos" around lights, frequent changes in eyeglass, fading or yellowing of colors etc. are symptoms of cataract.