The reduction of horizontal inequity in unmet refractive error: The Shahroud Eye Cohort Study, 2009–2014

PURPOSE: To measure Horizontal Inequity Index (HI) of unmet refractive error and its changes between 2009 and 2014 in Iran. METHODS: The data used in this study was taken from population-based study, Shahroud Eye Cohort Study. The number of participants analyzed in first (2009) and second phases of study (2014) were 5190 and 4737, respectively, and individuals between 40 and 64 years were included. The HI was determined by using the Concentration Index (C) based on the nonlinear (Probit) model, and C was decomposed to identify and quantify the contribution of each factor. RESULTS: After adjusting for need variables, the results demonstrated that the HI in unmet refractive need decreased from −0.288 (95% CI: 0.370, −0.206) in the 2009 to −0.132 (95% CI: 0.290, −0.028) in 2014. Decomposition of the C showed that level of education and economic status were the greatest contributors with shares of 26.2% and 17.9%, respectively, in reducing the amount of HI in unmet refractive error between 2009 and 2014. CONCLUSIONS: The current study demonstrated that unmet refractive error did not have an equal distribution among economic quintiles, despite the same need for correcting refractive errors. Reducing the amount of HI in unmet refractive error between 2009 and 2014 indicated an improvement in the unmet need in the five years period between two phases of study.