Association of Diabetic Retinopathy Severity with Glycated Haemoglobin and Serum Triglycerides in Patients with Type 2 Diabetes Mellitus: A Cross-Sectional Observational Study from South India

Abstract

 Background: Diabetic Retinopathy (DR) is a major microvascular complication of Type 2 Diabetes Mellitus (T2DM), with poor glycaemic control and dyslipidaemia being important potentially modifiable risk factors. However, the association between serum triglycerides and the severity of DR remains inconsistent across populations. This study evaluated the association of glycated haemoglobin (HbA1c) and serum triglyceride levels with DR severity among patients with T2DM in a South Indian tertiary-care setting. Methods: A cross-sectional observational study was conducted at the Karnataka Institute of Endocrinology and Research, Bengaluru, India. Adults aged >18 years with confirmed T2DM were included. Patients with type 1 diabetes mellitus and retinal diseases other than diabetic retinopathy were excluded. All participants underwent ophthalmic examination and DR was graded according to the International Clinical Diabetic Retinopathy Severity Scale. HbA1c, serum triglycerides, HDL, LDL, total cholesterol, fasting and postprandial blood glucose, serum creatinine, blood urea, vitamin D and TSH were measured. Participants were categorised according to HbA1c and triglyceride levels. Associations between categorical variables were assessed. Results: A total of 344 patients with T2DM were included. Diabetic retinopathy was present in 105 (30.5%) participants, comprising mild NPDR in 52 (15.1%), moderate NPDR in 29 (8.4%), severe NPDR in 15 (4.4%) and PDR in 9 (2.6%). HbA1c showed a significant association with DR severity (p<0.001); severe NPDR and PDR occurred only among participants with HbA1c >8.0%. The association between triglyceride category and DR was not statistically significant (χ² = 10.933, p = 0.206), although the proportion without DR decreased across increasing triglyceride categories. Fasting and postprandial blood glucose, LDL cholesterol and total cholesterol differed significantly across DR severity groups. Conclusion: This study showed that poor glycaemic control was strongly associated with increasing severity of diabetic retinopathy. Serum triglyceride categories showed a non-significant trend towards greater DR frequency.