Epidemiology in the design and evaluation of blindness control programs.
D000367:Age Factors; D001766:Blindness / Q000209:etiology / Q000517:prevention & control*; D002648:Child; D002675:Child, Preschool; D003315:Cornea; D003318:Corneal Opacity / Q000209:etiology; D003365:Costs and Cost Analysis; D003906:Developing Countries; D004544:El Salvador; D004812:Epidemiologic Methods; D005069:Evaluation Studies as Topic; D005128:Eye Diseases / Q000517:prevention & control; D006801:Humans; D007223:Infant; D010865:Pilot Projects; D011787:Quality of Health Care; D012424:Rural Population; D012621:Seasons; D014505:Urban Population; D014801:Vitamin A / Q000008:administration & dosage; D014802:Vitamin A Deficiency / Q000453:epidemiology; D014985:Xerophthalmia / Q000517:prevention & control
D014801:Vitamin A