Comparative analysis of retinal thickness between type 1 and type 2 diabetes mellitus patients with similar disease duration: A cross-sectional study.

Purpose: To assess the retinal thickness in patients with type 1 diabetes mellitus (T1DM) and type 2 DM (T2DM) of equal disease duration, comparing them with age- and sex-matched healthy controls.

Methods: This cross-sectional, comparative, and observational study included 96 participants, categorized into four groups: A1 (patients with T1DM, n = 24), A2 (age- and sex-matched nondiabetic controls for A1, n = 24), B1 (patients with T2DM, n = 24), and B2 (age- and sex-matched nondiabetic controls for B1, n = 24). Evaluations included retinal nerve fiber layer (RNFL) thickness, ganglion cell complex (GCC) thickness, central macular thickness (CMT), visual acuity, color vision, and contrast sensitivity. The primary objective was to compare RNFL, GCC, and CMT between T1DM and T2DM patients with equivalent disease duration and their respective controls. Secondary analyses assessed differences in visual acuity, color vision, and contrast sensitivity between T1DM and T2DM patients.

Results: The mean age of T2DM patients was 50.96 years, and for T1DM patients it was 28.96 years. T2DM patients exhibited significant GCC reduction in the superonasal (P = 0.046) and inferonasal quadrants (P = 0.048) compared to T1DM. T2DM also showed significant RNFL thinning in the superior (P = 0.037), inferior (P = 0.012), and temporal quadrants (P = 0.025) compared to T1DM after adjustment for age and DM duration. No significant difference in CMT was observed between T1DM and T2DM. In T1DM patients, mean best-corrected visual acuity was significantly worse than that of controls (P = 0.019). Contrast sensitivity and color vision did not differ significantly between T1DM and T2DM.

Conclusion: This study reveals earlier RNFL and GCC thinning in T2DM compared to T1DM.