Abstract
Background: Visual acuity, like many other health-related problems, does not have an equal distribution in terms of
socio-economic factors. We conducted this study to estimate and decompose economic inequality in presenting visual
acuity using two methods and to compare their results in a population aged 40-64 years in Shahroud, Iran.
Methods: The data of 5188 participants in the first phase of the Shahroud Cohort Eye Study, performed in 2009, were used
for this study. Our outcome variable was presenting vision acuity (PVA) that was measured using LogMAR (logarithm of
the minimum angle of resolution). The living standard variable used for estimation of inequality was the economic status
and was constructed by principal component analysis on home assets. Inequality indices were concentration index and
the gap between low and high economic groups. We decomposed these indices by the concentration index and BlinderOaxaca
decomposition approaches respectively and compared the results.
Results: The concentration index of PVA was -0.245 (95% CI: -0.278, -0.212). The PVA gap between groups with a high
and low economic status was 0.0705 and was in favor of the high economic group. Education, economic status, and age
were the most important contributors of inequality in both concentration index and Blinder-Oaxaca decomposition.
Percent contribution of these three factors in the concentration index and Blinder-Oaxaca decomposition was 41.1% vs.
43.4%, 25.4% vs. 19.1% and 15.2% vs. 16.2%, respectively. Other factors including gender, marital status, employment
status and diabetes had minor contributions.
Conclusion: This study showed that individuals with poorer visual acuity were more concentrated among people with a
lower economic status. The main contributors of this inequality were similar in concentration index and Blinder-Oaxaca
decomposition. So, it can be concluded that setting appropriate interventions to promote the literacy and income level
in people with low economic status, formulating policies to address economic problems in the elderly, and paying more
attention to their vision problems can help to alleviate economic inequality in visual acuity.