Temporal Sector Thickening of the Retinal Nerve Fiber Layer as a Structural Marker of Diabetic Retinopathy Severity in Chinese Adults with Type 2 Diabetes Mellitus

PURPOSE: To investigate alterations in peripapillary retinal nerve fiber layer (pRNFL) thickness in Chinese adults with type 2 diabetes mellitus and assess their association with the presence and severity of diabetic retinopathy (DR). METHODS: This cross-sectional study was conducted within the Fushun Diabetic Retinopathy Cohort (FS-DIRECT). Participants underwent standardized ophthalmic examinations, six-field fundus photography, and Spectralis optical coherence tomography. Eyes were classified as no DR, non-proliferative DR (mild, moderate, or severe), or proliferative DR. Automated pRNFL measurements were pbtained for six sectors. Group differences were analyzed using t-tests and analysis of variance. Factors associated with pRNFL thickness were evaluated using univariate and multivariable linear regression. RESULTS: A total of 833 right eyes were included, of whom 273 had DR and 560 did not. Global pRNFL thickness did not differ between groups (107.21 ± 17.59 µm vs. 105.91 ± 13.82 µm, P = 0.510). In contrast, the temporal sector was significantly thicker in eyes with DR (82.37 ± 20.72 µm vs. 76.22 ± 15.57 µm, P < 0.001) and showed progressive thickening with increasing DR severity (76.22 ± 15.57 µm in no DR vs. 94.53 ± 30.10 µm in severe/proliferative DR, P < 0.001). In multivariable analysis, DR severity remained the only independent predictor of temporal thickening (β = 3.70, P < 0.001). CONCLUSIONS: Temporal-but not global-pRNFL thickening was independently associated with DR severity. These findings support region-specific neuroaxonal alterations in DR and highlight temporal pRNFL thickening as a potential structural marker of diabetic retinal nerve damage.