A cataract is what you get when the normally transparent lens of the eye becomes cloudy. It mostly happens with age. Vision loss from a cataract is easily treated by relatively inexpensive surgery. You should seek guidance from an ophthalmologist about if cataract surgery is appropriate for you.

The Royal College of Ophthalmologists has a good patient information leaflet on cataract, written in plain english. Do bear in mind, though, that it is aimed at people in the UK.

Incidentally India has a huge and growing backlog of cataract cases, mostly because the poor are unaware that it can be treated, and because they have trouble affording even subsidized surgery. There have been attempts to handle the backlog with large, subsidized, eye camps