Quadrant-wise macular thickness changes in type II diabetes mellitus without clinically detectable retinopathy

Abstract

Background: Type 2 Diabetes Mellitus (T2DM) is associated with early retinal alterations that may precede clinically detectable diabetic retinopathy (DR). Spectral-domain optical coherence tomography (SD-OCT) enables quantitative assessment of macular thickness and may facilitate the detection of subclinical retinal changes. This study evaluated quadrant-wise macular thickness in patients with T2DM without DR and examined its association with disease duration and glycaemic status. Materials and Methods: This hospital-based cross-sectional observational study included 141 participants aged 40–80 years, comprising 77 healthy controls and 64 patients with T2DM without clinically detectable DR. All participants underwent comprehensive ophthalmic examination and SD-OCT macular imaging. Macular thickness was measured in the nine ETDRS quadrants. Diabetic participants were stratified according to random blood sugar (RBS) levels (<200 or ≥ 200 mg/dL) and diabetes duration (<10 years or ≥ 10 years). Results: Patients with T2DM demonstrated significantly greater central macular thickness (p=0.043) and superior outer macular thickness (p=0.037) than healthy controls, while no significant differences were observed in the remaining quadrants. Macular thickness did not differ significantly between RBS subgroups. Compared with controls, patients with diabetes duration <10 years had significantly greater central macular thickness (p=0.006), whereas those with duration ≥ 10 years showed significantly greater temporal outer macular thickness (p=0.031). However, no statistically significant differences were found between the two diabetes-duration groups. Conclusion: Patients with T2DM without clinically detectable DR exhibit subtle, quadrant-specific increases in macular thickness detectable by SD-OCT. These changes appear to be influenced by disease duration rather than current glycaemic status.