The term visual impairment referrs to blindness and partial-sightedness.  Sight loss can be sudden and severe, or it can be a gradual deterioration over a long period of time.  Nearly 2 million people in the UK have significant sight loss, but very few people experience complete loss of vision, meaning that any remaining eyesight needs to be maximised.  Developing sight loss is not just part of getting older, it can be as a result of medical conditions - such as cataracts, age-related macular degeneration or diabetes -- so you should get any decline in your sight checked at an opticians.