title: Myopia and diabetic retinopathy: A systematic review and meta-analysis.
abstract: OBJECTIVE
  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.
authors.affiliation: Cancer Research Institute, Central South University, Changsha 410078, Hunan, China; Department of Surgery, Second Xiangya Hospital, Central South University, Changsha 410011, Hunan, China.
authors.forename: Xiang
authors.initials: X
authors.lastname: Wang
authors.affiliation: Department of Ophthalmology, Second Xiangya Hospital, Central South University, Changsha 410011, Hunan, China; Eye Research Institute, Second Xiangya Hospital, Central South University, Changsha, Hunan 410011, China.
authors.forename: Luosheng
authors.initials: L
authors.lastname: Tang
authors.affiliation: Department of Ophthalmology, Second Xiangya Hospital, Central South University, Changsha 410011, Hunan, China; Eye Research Institute, Second Xiangya Hospital, Central South University, Changsha, Hunan 410011, China.
authors.forename: Ling
authors.initials: L
authors.lastname: Gao
authors.affiliation: Department of Ophthalmology, Second Xiangya Hospital, Central South University, Changsha 410011, Hunan, China; Eye Research Institute, Second Xiangya Hospital, Central South University, Changsha, Hunan 410011, China.
authors.forename: Yujia
authors.initials: Y
authors.lastname: Yang
authors.affiliation: Department of Ophthalmology, Second Xiangya Hospital, Central South University, Changsha 410011, Hunan, China; Eye Research Institute, Second Xiangya Hospital, Central South University, Changsha, Hunan 410011, China.
authors.forename: Dan
authors.initials: D
authors.lastname: Cao
authors.affiliation: Department of Ophthalmology, Second Xiangya Hospital, Central South University, Changsha 410011, Hunan, China; Eye Research Institute, Second Xiangya Hospital, Central South University, Changsha, Hunan 410011, China. Electronic address: amyli@csu.edu.cn.
authors.forename: Yunping
authors.initials: Y
authors.lastname: Li
mesh_terms: D015331:Cohort Studies; D003430:Cross-Sectional Studies / Q000706:statistics & numerical data; D003930:Diabetic Retinopathy / Q000150:complications / Q000453:epidemiology*; D006801:Humans; D009216:Myopia / Q000150:complications / Q000453:epidemiology*; D016017:Odds Ratio
keywords: Association; Axial length; Diabetic retinopathy; Myopia; Odds ratio