Comparison of macular thickness by optical coherence tomography in newly diagnosed type 2 diabetes mellitus patients in their hyperglycaemic and euglycaemic states

Objectives: This study aimed to evaluate dynamic changes in central macular thickness (CMT) in newly diagnosed type 2 diabetes mellitus (T2DM) patients by assessing measurements at baseline (hyperglycaemic state) and after achieving glycaemic control (euglycaemic state) using optical coherence tomography (OCT). The goal was to detect early subclinical retinal changes that may precede clinical diabetic retinopathy (DR). Materials and Methods: A prospective, longitudinal, hospital-based observational study was conducted on 111 newly diagnosed T2DM patients. Each patient underwent serial CMT measurements using spectral-domain OCT, recorded every 10–15 days from initial presentation in a hyperglycaemic state through to euglycaemic stabilisation. At each visit, visual acuity, fundus examination, random blood sugar and CMT were documented. Results: Majority of the patients were older adults (66.6% aged ≥61 years), and 61% were male. At baseline, 73.9% had moderate visual impairment (6/12–6/24), and 43.3% showed early signs of DR, mostly mild non-proliferative DR. Over the follow-up period, improvements were observed in both visual acuity and retinal status, particularly in those achieving better glycaemic control. Mean CMT significantly decreased in both eyes between the hyperglycaemic and euglycaemic states (right eye: 259 ± 28 µm to 245 ± 30 µm; left eye 255 ± 11 µm to 248 ± 13 µm; P < 0.05). Elevated haemoglobin A1C levels were associated with less favourable retinal outcomes. Conclusion: CMT was significantly elevated during initial hyperglycaemia, even in the absence of overt DR, indicating early subclinical retinal changes. These findings underscore the value of OCT as a sensitive tool for early retinal assessment and highlight the importance of prompt glycaemic control in newly diagnosed T2DM patients.