/Ophthalmology in the Tropics and Subtropics/WORLD BLINDNESS 4-u1.0-B978-1-4160-4470-3..50022-7--cesec2 4-u1.0-B978-1-4160-4470-3..50022-7..DOCPDF Chapter 18 4-u1.0-B978-1-4160-4470-3..50022-7 4-u1.0-B978-1-4160-4470-3..50022-7 WHO categories of visual impairment 4-u1.0-B978-1-4160-4470-3..50022-7--cesec3 WHO categories of visual impairment Ophthalmology in the Tropics and Subtropics Section 3 4-u1.0-B978-1-4160-4470-3..50022-7--cesec2 System-oriented Disease hubsection 4 section System-oriented Disease Section 3 4-u1.0-B978-1-4160-4470-3..50022-7 4-u1.0-B978-1-4160-4470-3..50022-7--cesec1 Ophthalmology in the Tropics and Subtropics 4-u1.0-B978-1-4160-4470-3..X5001-0--section3 Ophthalmology in the Tropics and Subtropics text/html; charset=ISO-8859-1 WORLD BLINDNESS Chapter 18 chapter bookContent 4-u1.0-B978-1-4160-4470-3..X5001-0--section3 WORLD BLINDNESS 4-u1.0-B978-1-4160-4470-3..50022-7 4-u1.0-B978-1-4160-4470-3..X5001-0--section3 4-u1.0-B978-1-4160-4470-3..50022-7 4-u1.0-B978-1-4160-4470-3..50021-5--cebib1 6 section 4-u1.0-B978-1-4160-4470-3..50022-7--cesec2 4-u1.0-B978-1-4160-4470-3..50022-7--cesec1 Chapter 18 Manson's Tropical Diseases 978-1-4160-4470-3 Cook 22nd
Chapter 18 – Ophthalmology in the Tropics and SubtropicsDavid H. Yorston,
D. D. Murray McGavin
WORLD BLINDNESSThe World Health Organization (WHO) Programme for the Prevention of Blindness and Deafness estimates that the number of people blind in the world is now around 37 million.[1] The figure does not take into account the many millions who have only partial sight, an estimated further 124 million.[1] Over 90% of blind people live in the developing world and at least 70% of blindness could be ‘avoided', that is, either prevented or cured.
WHO categories of visual impairmentAt one time there were over 70 different definitions of blindness among United Nations member states. The WHO has now defined five categories of visual impairment (Table 18.1).
Table not available in preview mode
Blindness is defined as a best-corrected binocular visual acuity of less than 3/60 (less than counting fingers at 3 m) or where the central visual field is less than 10° around fixation in the better eye. Agreed definitions allow comparisons between …
