Continuous glucose monitoring time in range, glycemic parameters for diabetic retinopathy in type 2 diabetes: A systematic review and meta-analysis

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Abstract

Background: Many patients with type 2 diabetes (T2D) develop diabetic retinopathy (DR) despite achieving target glycated hemoglobin (HbA1c) levels. Continuous glucose monitoring (CGM)-derived metrics capture glucose variability beyond HbA1c, yet systematic evaluations of their associations with DR across multiple CGM parameters remain limited.
Objective: This study aimed to evaluate correlations between five CGM metrics and DR in T2D.
Study design: Systematic review and meta-analysis.
Methods: This systematic review was registered on the International Prospective Register of Systematic Reviews (PROSPERO) (CRD42024613889). Six electronic databases were systematically searched from inception to April 1, 2026, for observational studies in T2D. The exposures of interest were CGM-derived metrics, including time in range (TIR), mean amplitude of glycemic excursions (MAGE), standard deviation of blood glucose (SDBG), mean blood glucose (MBG), and coefficient of variation (CV). The primary outcome was DR. Standardized mean differences (SMDs) with 95% confidence intervals (CIs) were synthesized.
Results: Ten studies (N = 6434) were included. Compared to non-DR controls, patients with DR had significantly lower TIR (SMD = −0.83, 95% confidence interval [CI]: −1.18 to −0.48; P < 0.001) and higher glycemic parameters, including MAGE (SMD = 1.53, 95% CI: 0.91–2.15; P < 0.001), SDBG (SMD = 1.10, 95% CI: 0.61–1.60; P < 0.001), MBG (SMD = 0.67, 95% CI: 0.25–1.09; P = 0.002), and CV (SMD = 0.38, 95% CI: 0.08–0.69; P = 0.014).
Conclusions: CGM metrics, particularly MAGE, SDBG, and TIR, are associated with prevalent DR in T2D, offering exploratory clinical insights alongside HbA1c. However, longitudinal prospective evidence is currently limited to TIR. Given the substantial heterogeneity across primary studies and the Very Low certainty of evidence per the Grading of Recommendations Assessment, Development and Evaluation (GRADE) framework, these metrics should be interpreted with caution and require prospective validation before clinical translation.

Keywords

Diabetic retinopathy / Time in range / Glycemic variability / Continuous glucose monitoring / Type 2 diabetes

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