Characteristics of eligible studies included in the meta-analysis.

Abbreviations: NIDDM: non-insulin-dependent diabetes mellitus. DM: diabetes mellitus. C-C: Case-control. PDR: proliferative diabetic retinopathy. DR: diabetic retinopathy. WHO: World Health Organization guidelines. ETDRS: the Early Treatment Diabetic Retinopathy Study. Polys: genotype combinations of polymorphisms. N/A: Not applicable.