The yazd eye study - A population-based survey of adults aged 40-80 years: Rationale, study design and baseline population data

Purpose: To describe the rationale, methodology and baseline data of the Yazd Eye Study, a study in the urban and rural areas of Yazd, a district in the center of Iran. Methods: This population-based cross-sectional study included adults aged 40-80 years from the non-institutionalized population of the Yazd district, in 2010-2011. Using multi-stage, systematic cluster random sampling and a probability proportional to size strategy, 58 clusters of 40 subjects were selected from 251 clusters in different enumeration areas. A detailed interview and eye examination were performed for each eligible participant. The eye examination included refraction testing, uncorrected and best corrected visual acuity testing, slit lamp biomicroscopy, Goldmann applanation tonometry, gonioscopy, dilated fundus examination, visual field, determination of central corneal thickness, and stereoscopic fundus photography. General health assessments and laboratory tests including hemoglobin, hematocrit, glycosylated hemoglobin, fasting blood sugar, serum lipids, and urine albumin to creatinine ratio were also performed to assess anthropometric and systemic risk factors. Results: Of 2320 eligible individuals, 2098 (response rate 90.4%) participated in the study. The mean ± standard deviation age of participants was 54.1 ± 10.0 years, and included 994 men (47.4%) and 1104 women (52.6%). Most participants lived in urban regions (89.2%) and were younger than 60 years old (72.0%). Among the participants, 20.1% were illiterate, and 40.9%, 28.0%, and 11.0% had primary, secondary and college or university level education, respectively. Conclusion: This study is expected to provide an estimate of the prevalence and risk factors of major eye diseases and normal eye indices in the Yazd district.