Subgroup analyses based on the type of DR showed that the effect size was statistically significant for proliferative DR (PDR) (DD vs. II: OR = 2.67, 95% CI 1.53-4.64; DD+ID vs. II: OR = 1.86, 95% CI 1.18-2.93; DD vs. ID+II: OR = 2.22, 95% CI 1.38-3.55), but not for background DR (BDR) (DD vs. II: OR = 1.38, 95% CI 0.85-2.25; DD+ID vs. II: OR = 1.40, 95% CI 0.98-2.02; DD vs. ID+II: OR = 1.15, 95% CI 0.74-1.79).