Correlation between HbA1c Levels and Severity of Diabetic Retinopathy in Patients with Type 2 Diabetes Mellitus: A Cross-Sectional Observational Study
Keywords:
Diabetic Retinopathy, HbA1c, Type 2 Diabetes Mellitus, ETDRS, Glycaemic Control, Non-Proliferative Diabetic Retinopathy, Proliferative Diabetic Retinopathy.Abstract
Background: Diabetic retinopathy is a major microvascular complication of type 2 diabetes mellitus, and chronic glycaemic exposure is a potentially modifiable determinant of retinal microvascular damage. HbA1c provides an integrated estimate of recent glycaemic control and may help identify patients at greater risk of advanced retinopathy.
Objective: To evaluate the association between HbA1c level and diabetic retinopathy severity in patients with type 2 diabetes mellitus.
Methods: This cross-sectional observational study included 48 patients with type 2 diabetes mellitus. Diabetic retinopathy severity was recorded using ETDRS-linked grades and grouped as no diabetic retinopathy, mild non-proliferative diabetic retinopathy (NPDR), moderate NPDR, severe NPDR, and proliferative diabetic retinopathy (PDR). HbA1c, diabetes duration, age, body mass index, treatment category, hypertension, dyslipidaemia, and macular oedema status were analysed. Spearman rank correlation and Kruskal-Wallis testing were used for ordinal and between-group comparisons.
Results: Mean age was 56.54 ± 9.98 years, mean diabetes duration was 14.08 ± 6.92 years, and mean HbA1c was 8.37 ± 1.81%. Retinopathy was absent in 7 (14.6%), while mild NPDR, moderate NPDR, severe NPDR, and PDR were present in 13 (27.1%), 13 (27.1%), 4 (8.3%), and 11 (22.9%), respectively. Mean HbA1c increased stepwise from 5.93% in patients without retinopathy to 10.93% in PDR. HbA1c correlated strongly with ETDRS grade (Spearman rho=0.967, p<0.001), and HbA1c differed significantly across severity groups (Kruskal-Wallis H=44.22, p<0.001). A partial rank analysis controlling for diabetes duration showed an attenuated but persistent association (partial rho=0.375, p=0.009).
Conclusion: Higher HbA1c levels were strongly associated with greater diabetic retinopathy severity in this clinical cohort. The association was partly explained by longer diabetes duration, but remained statistically significant after accounting for duration. These findings support the clinical importance of sustained glycaemic control together with regular retinal surveillance in patients with type 2 diabetes mellitus.
