Rates of Progression in Diabetic Retinopathy During Different Time Periods: A systematic review and meta-analysis

OBJECTIVE: This meta-analysis reviews rates of progression of diabetic retinopathy to proliferative diabetic retinopathy (PDR) and/or severe visual loss (SVL) and temporal trends. RESEARCH DESIGN AND METHODS: This systematic literature review and meta-analysis of prospective studies assesses progression of retinopathy among diabetic patients without treatment for retinopathy at baseline. Studies published between 1975 to February 2008 were identified. Outcomes of interest were rates of progression to PDR and/or SVL. Pooled baseline characteristics and outcome measures were summarized using weighted averages of counts and means. Baseline characteristics and outcomes were compared between two periods: 1975–1985 and 1986–2008. RESULTS: A total of 28 studies comprising 27,120 diabetic patients (mean age 49.8 years) were included. After 4 years, pooled incidence rates for PDR and SVL were 11.0 and 7.2%, respectively. Rates were lower among participants in 1986–2008 than in 1975–1985. After 10 years, similar patterns were observed. Participants in 1986–2008 studies had lower proportions of PDR and non-PDR at all time points than participants in 1975–1985 studies. CONCLUSIONS: Since 1985, diabetic patients have lower rates of progression to PDR and SVL. These findings may reflect an increased awareness of retinopathy risk factors; earlier identification and initiation of care for patients with retinopathy; and improved medical management of glucose, blood pressure, and serum lipids. Differences in baseline characteristics, particularly in the prevalence and severity of retinopathy, could also have contributed to these temporal differences.