To objectively evaluate the alteration of interdigitation zone (IZ) length in diabetic patients and to determine its relationship with diabetic retinopathy (DR) progression.

Prospective cohort study.

Two hundred and thirty-one diabetic patients (231 eyes) were included. DR was graded according to the modified Airlie House classification system. The high-resolution spectral-domain optical coherence tomography (SD-OCT) images were obtained to calculate the length of IZ using Image-Pro Plus. Linear regression analysis and logistic regression analysis were performed to determine the associations between IZ length with DR severity and DR progression.

IZ length was significantly reduced in DR patients compared to that in diabetic patients without DR (NDR) (3.758 ± 1.653 mm vs 5.722 ± 0.865 mm, P < .001). After adjusting for confounding factors, IZ length showed a negative association with DR severity, and longer IZ length correlated with better best corrected visual acuity (BCVA) (ß −0.021, 95% CI −0.030 to −0.011, P < .001). Forty eyes (21.98%) developed DR progression over 3-year follow-up. Notably, longer IZ length at baseline was associated with lower risk of DR progression over 3-year follow-up (OR 0.039, 95% CI 0.011-0.139, P < .001). The logistic regression models predicted DR progression with area under the curve (AUC) of 0.917 (95% CI 0.872-0.962) and 0.953 (95% CI 0.917-0.989) respectively based only on IZ length and IZ length combined with established risk factors.

IZ length decreased with DR severity and significantly correlated with DR progression, potentially serving as a new predictor for disease progression.