Myopia and diabetic retinopathy: A systematic review and meta-analysis

Aims: Myopia may have protective effects against diabetic retinopathy (DR). However, the data from epidemiologic studies are inconsistent. We aimed to examine the association between myopia and DR by conducting a meta-analysis. Methods: We identified studies by searching the PubMed and EMBASE databases. Study-specific odds ratios (ORs) were pooled using a fixed or random effects model. Myopic eyes were defined as having a spherical equivalent (SE) < -0.5 diopters (D). Myopic SE, each diopter decrease in SE toward myopia, and each millimeter increase in axial length (AL) were used as independent surrogate variables for myopia. Results: Data from 6 population-based and 3 clinic-based studies were included in the analyses. Myopic SE (compared with emmetropic eyes) and each millimeter increase in AL were associated with a decreased risk for DR (pooled odds ratio [OR], 0.80 and 0.79, respectively; 95% confidence interval [CI], 0.67-0.95 and 0.73-0.86, respectively; P=0.011 and 0.000, respectively). Each millimeter increase in AL was also associated with a decreased risk for vision-threatening diabetic retinopathy (VTDR) (pooled OR, 0.70; 95% CI, 0.60-0.82; P=0.000). No significant association between each diopter decrease in SE and DR was observed. Conclusions: Our meta-analysis suggests that individuals with myopia exhibit a decreased risk of developing DR or VTDR. An increased AL plays a critical role in this protective effect. (C) 2015 Elsevier Ireland Ltd. All rights reserved.