1. Blindness and vision impairment. World Health Organization. www.who.int/news-room/fact-sheets/detail/blindness-and-visual-impairment
2. Avoidable blindness. Orbis International. www.orbis.org/en/avoidable-blindness
3. Vision atlas. The International Agency for the Prevention of Blindness. www.iapb.org/learn/vision-atlas/