DISTRIBUTION AND ETIOLOGY OF BLINDNESS AND VISUAL IMPAIRMENT IN MESOENDEMIC ONCHOCERCAL COMMUNITIES, KADUNA STATE, NIGERIA

During a field trial of ivermectin in Kaduna State, northern Nigeria, 6831 people aged 5 years and over, living in 34 mesoendemic savannah o nchocercal communities were examined for ocular disease. Visual functi on assessments included tests of visual acuity and visual fields. A to tal of 185 individuals (2.7%) were bilaterally blind by acuity criteri a with a further 42 blind by field constriction. The overall prevalenc e of blindness was 3.3%. A. further 115 individuals were visually impa ired by WHO criteria. Examination for the cause of blindness revealed that 43% of eyes in bilaterally blind patients were blind because of o nchocerciasis. A further 11% were blind from optic atrophy much of whi ch was probably onchocercal in origin. Glaucoma was the next most comm on cause of blindness in the bilaterally blind (11%). Only 6% of eyes were blind from cataract as the primary cause. In the visually impaire d population cataract was the most common primary cause of impaired/bl ind eyes (31%), followed by onchocerciasis (19%).