Why in odd ages the eye sight becomes foggy? How can this defect may be removed?

Sometimes, particularly in old age, eyesight becomes foggy. It is due to the eye lens becoming milky and cloudy. When it happens, persons are said to have cataract. There is a loss of vision, sometimes extremely severe. It is possible to treat this defect. The opaque lens is removed and a new artificial lens is inserted. Modern technology has made this procedure simpler and safer.