TrachomaChlamydia trachomatisBlindnessNight BlindnessBlindness, CorticalVision, LowOnchocerciasis, OcularCataractVisually Impaired PersonsXerophthalmiaEye Diseases, HereditaryVisual AcuityEye DiseasesVision DisordersGlaucomaCataract ExtractionRefractive ErrorsVitamin A DeficiencyEye InjuriesElectroretinographyMacular DegenerationCorneal Diseases