title: Avoidable blindness: a world problem.
mesh_terms: D001766:Blindness / Q000209:etiology / Q000517:prevention & control*; D002386:Cataract / Q000150:complications; D006801:Humans; D009855:Onchocerciasis / Q000150:complications; D013019:South Africa; D014141:Trachoma / Q000150:complications; D014985:Xerophthalmia / Q000150:complications