Pilot study for a blindness prevalence survey in the state of Sonora Mexico

Purpose. To establish the feasibility of carrying out a population based blindness survey in Mexican Hispanics 40 years and older of the state of Sonora. Methods. A community was randomly selected from all communities within 2 hours drive from the city of Nogales. A house to house census identified 178 persons age 40 and older of which 171 (96%) completed a home questionnaire. All persons were asked to be examined at a central site within the town. In 3 days, 2 ophthalmologist, and an ophthalmic technician performed ophthalmic examinations on 118 of the 178 eligible individuals; an additional 43 persons arrived at the site but were not examined due to time constraints. 16 persons (9.9%) refused to participate. Results. The prevalence of diabetes by self description was 11.3%, a figure comparable to others reported from Mexico City. 30% of the participants had presenting visual acuity worse than 20/40 in the better eye, but 78% of them improved with refraction to 20/40 or better. 3.4% had cataract surgery in at least one eye and 12.7 has some lens opacity. Conclusion. This pilot study shows the feasibility of carrying out a survey for visual impairment in a stable Hispanic population, and the full study will provide much needed data on blindness and visual impairment in a Hispanic population.