Aim:
To evaluate the clinical significance of serum L-selectin (sCD62L) levels as a biomarker of retinal damage in patients with type 2 diabetes mellitus (T2DM) by correlating its concentration with the stages of diabetic retinopathy (DR) and clinical and morphological parameters of the retinal state.

Material and Methods:
A total of 124 patients (124 eyes) were examined: 95 patients with T2DM (ranging from mild non-proliferative to proliferative DR) and 29 age- and sex-matched controls. Diagnostic techniques included BCVA assessment, SD-OCT (Topcon 3D OCT-1000), and serum ELISA for L-selectin determination.

Results:
A significant 2.5-fold increase in serum L-selectin levels was identified in the T2DM cohort compared to controls ([mean ± standard error] 31.2 ± 8.6 ng/mL vs. 12.5 ± 3.5 ng/mL; p < 0.001). A progressive upward trend in marker concentration was observed relative to pathology severity: from (median [interquartile range]) 24.7 (20.4–29.0) ng/mL in mild non-proliferative DR (p < 0.001 vs. control group [12.5 (10.1–14.9)] ng/mL) to 39.5 (35.1–43.9) ng/ mL in the proliferative stage (p < 0.001 vs. control group). Positive correlations were found between L-selectin levels and HbA1c (rs = 0.816, p < 0.001), as well as central retinal thickness (rs = 0.467, p = 0.002).

Conclusions:
CD62L is a significant biomarker of systemic inflammation and vascular dysfunction in T2DM, reflecting the severity of diabetic retinopathy and the risk of blood-retinal barrier disruption.