Prevalence of Retinopathy in Prediabetic Populations: A Systematic Review and Meta-Analysis

Abstract

Among the leading causes of vision impairment and blindness globally, diabetic retinopathy (DR) is one of the most important causes. There is increasing evidence of DR prevalence in the prediabetic population. This systematic review presents collective data on retinopathy in the prediabetic population. This review article aimed to estimate the reported prevalence of retinopathy in prediabetes, impaired glucose tolerance test (GTT) without diabetes mellitus, and the risk factors involved and to summarize it. Literature searches were done using the Web of Science, CINAHL, Google Scholar, Cochrane, EMBASE, and PubMed databases from inception to April 2023. Our search included the words prediabetes, DR, and risk factors. All searches were looked at for methodological quality and evidence. Thirty-one studies were included after the screening. Population-based data were used in 23 studies (82.1%). The prediabetic population screened was 10,539. The prevalence of retinopathy ranged between 0.3% and 20.9%, showing a median of 8.1% with an interquartile range (IQR) of 4.2-11%, showing great variance in estimates due to the use of different screening methods, methods used for retinopathy grading, and study populations. Several studies compared the population with normal GTT with impaired glucose tolerance (IGT) and inferred that there was a lower prevalence of retinopathy in the normal GTT population (3.0%, IQR 0.3-7.4%) than prediabetes (6.7%, IQR 1.9-10.1%). According to this data, a greater retinopathy prevalence was found in prediabetic populations.

Keywords: diabetic retinopathy; impaired fasting glucose; impaired glucose tolerance; prediabetes; prevalence.

Figure 1. PRISMA flowchart showing the study selection process

Figure 2. Forest plot of the prevalence of retinopathy in the prediabetic population from the included studies

∗ Prediabetes group size estimated from the reported retinopathy prevalence and the number of affected individuals. ∗∗ Aggregate prevalence estimates presented for impaired fasting glucose (IFG), impaired glucose tolerance (IGT), and combined IFG and IGT (IFG-IGT). All studies are population-based, except three hospital-based studies (lavender highlights) and two randomized-controlled trials (yellow highlights). CI: confidence interval

Figure 3. Forest plot of the prevalence of retinopathy in the prediabetic population and NGT from included studies reporting data for both groups

Normal glucose tolerance (NGT) prevalence estimates in red and prediabetes prevalence estimates in blue. ¹ Prediabetes group size estimated from reported retinopathy prevalence and number of affected individuals. ² Impaired fasting glucose (IFG), impaired glucose tolerance (IGT), and combined IFG and IGT (IFG/IGT) retinopathy prevalence estimates aggregated with total prediabetes group size used for 95% confidence interval (CI) estimation. ³ NGT group size estimated from the total study sample minus the reported prediabetes population. ⁴ Prediabetes group size estimated from reported retinopathy prevalence and number of affected individuals. All studies are population-based, except two hospital-based studies (lavender highlights).