Prevalence and causes of avoidable blindness and visual impairment, including the prevalence of diabetic retinopathy in Siwan district of Bihar, India: A population-based survey

Purpose: The aim of this study was to estimate the prevalence and causes of visual impairment (VI) and blindness and diabetic retinopathy (DR) in Siwan district, Bihar. Methods: A population-based cross-sectional study was done from January to March 2016 using the Rapid Assessment of Avoidable Blindness 6 (RAAB 6, incorporating DR module) methodology. All individuals aged >/=50 years were examined in 57 randomly selected clusters within the district. Results: A total of 3476 individuals were enumerated and 3189 (92%) completed examination. The overall prevalence of blindness and severe VI was 2.2% (95% confidence interval (CI): 1.6-2.8) and 3.4% (95% CI: 2.6-4.3), respectively. Untreated cataract was the leading cause of blindness (73%) and severe VI (93%). The cataract surgical coverage (CSC) at <3/60 was 71.5% for eyes and 89.3% for persons in this sample and the CSC was similar between the genders. Refractive error (71%) was the primary cause of early VI. The overall prevalence of known and newly diagnosed diabetes was 6.3% (95% CI, 5.4-7.2%). Prevalence of any DR, maculopathy, and sight-threatening DR was 15, 12.4, and 6%, respectively. Conclusion: To conclude, as compared to previous reports, the prevalence of blindness and DR in Siwan district of Bihar was found to be lower and the CSC was higher. However, the problem of avoidable blindness remains a major problem in this region.