Vol. 7, Issue 1, Part A (2025)

Background: Diabetes mellitus (DM) microvascular complications consist of diabetic retinopathy (DR) and diabetic macular edema (DME) which result in permanent vision loss. Early detection of retinal structural changes including central retinal thickness (CRT) and macular thickness and retinal nerve fiber layer (RNFL) thickness can be achieved through optical coherence tomography (OCT). The understanding of diabetes duration in relation to retinal thickness parameters enables early detection and treatment of the condition.

Objective: To assess the impact of duration of diabetes mellitus on retinal thickness parameters on SD-OCT and to investigate the relationship between the duration of the disease and the occurrence of DME in adult diabetic patients.+

Methods: This observational cross-sectional study involved 350 diabetic patients of both type 1 and type 2 from Tikrit Teaching Hospital and a private ophthalmology clinic in Iraq, during February 2024 and February 2025. Patients were stratified into three groups based on duration of diabetes: Group A (<5 years), Group B (5-10 years) and Group C (≥ 10 years). Retinal imaging was carried out using Heidelberg Spectralis SD-OCT. The parameters measured included CRT, average macular thickness, RNFL thickness and the presence of DME. Clinical and biochemical information such as HbA1c, fasting blood glucose, BMI and blood pressure were also recorded. Data were analyzed using SPSS version 26.

Results: Group C with the longest diabetes duration had the highest CRT (270 ± 29 µm), macular thickness (306 ± 30 µm) and DME incidence (30.4%) compared to groups A and B (p < 0.001). The RNFL thickness showed a decline with increase in disease duration (Group A: 102 ± 9 µm; Group C: 94 ± 11 µm). Pearson correlation analysis showed a high positive correlation between the duration of diabetes and both CRT (r = +0.62) and macular thickness (r = +0.59) and a moderate negative correlation with RNFL thickness (r = -0.48) all p < 0.001.

Conclusion: Longer duration of diabetes mellitus is related with increased retinal thickness and higher DME prevalence and progressive decrease in RNFL thickness. This study highlights the need for regular retinal examination using OCT especially in patients with prolonged diabetes for early detection and management.