Astigmatism in underserved rural areas: a population based study

PurposeStudying the prevalence of astigmatism and its related factors in underprivileged rural areas in Iran. MethodsUsing random cluster sampling, two rural areas in the north and southwest of Iran were randomly selected, and 3851 persons over 1year of age were invited to the study. In addition to recording demographics, retinoscopic refraction was conducted using baseline auto-refraction results. The prevalence of astigmatism was determined based on cylinder error cut-off points of 0.50dioptre (D), 1.00, 2.00 and 3.00D. Multiple logistic regression was used to assess variables' relationship with astigmatism. ResultsThe prevalence of astigmatism as a cylinder error greater than 0.50D was 35.6% (95% CI: 33.7-37.6); this was 34.0% (95% CI: 31.4-36.6) in women and 36.9% (95% CI: 33.9-39.9) in men. The lowest prevalence was seen in the 6-20year old age group (13.6%) and the highest prevalence was found in individuals older than 70years (82.5%). In the multiple logistic regression model, age and education level were significantly related to astigmatism. The prevalence rates of with-the-rule (WTR), against-the-rule (ATR), and oblique astigmatism were respectively 15.0%, 17.2%, and 3.5%. The prevalence of WTR astigmatism decreased with age, while the prevalence of ATR (and oblique astigmatism to a lesser extent) increased. ConclusionThe prevalence of astigmatism was similar to previous studies; however, there were considerable age-related changes. In particular, the prevalence of astigmatism in elderly people was substantial and of concern, particularly given that virtually none of this age group were wearing distance spectacles.