AIM: To investigate the correlation and diagnostic performance between baseline ocular parameters and the occurrence of retinopathy in patients with type 2 diabetes mellitus(T2DM)without retinopathy.METHODS: From May 2020 to May 2021, our hospital admitted a total of 123 patients with type 2 diabetes mellitus(T2DM)who had no retinopathy at baseline. Clinical data and ocular parameters at baseline were prospectively collected, followed by at least a 3-year follow-up period. The number of cases of diabetic retinopathy occurred during the follow-up period was statistically analyzed, and a multivariable Logistic regression analysis was conducted to identify factors associated with the development of diabetic retinopathy. ROC curve analysis was performed on the factors identified in the multivariable Logistic regression analysis.RESULTS: During the follow-up period, 49 patients(39.8%)developed diabetic retinopathy. Patients who developed retinopathy were included in the retinopathy group, while the remaining patients were included in the non-retinopathy group(n=74). The fasting blood glucose, glycated hemoglobin(HbA1c), anterior chamber depth, and central corneal thickness were higher in the retinopathy group than in the non-retinopathy group(all P<0.01), while the axial length and pupil diameter were lower in the retinopathy group than in the non-retinopathy group(all P<0.01). Low fasting blood glucose, HbA1c, and central corneal thickness are protective factors against diabetic retinopathy in T2DM patients [OR(95% CI): 0.356(0.130-0.978), 0.213(0.057-0.797), 0.971(0.950-0.992), all P<0.05], while low pupil diameter is a risk factor for diabetic retinopathy in T2DM patients [OR(95% CI): 389.483(20.298-7473.596), P<0.05]. ROC curve analysis showed that the AUC was highest when combining fasting blood glucose, HbA1c, central corneal thickness, and pupil diameter, at 0.962(95% CI: 0.934-0.991). The AUC values for the central corneal thickness and pupil diameter were 0.725(95% CI: 0.596-0.814)and 0.711(95% CI: 0.602-0.814), respectively, which were not significantly different from the AUC values of fasting blood glucose 0.709(95% CI: 0.615-0.803)and HbA1c 0.708(95% CI: 0.613-0.804), while the combined diagnosis of central corneal thickness and pupil diameter can increase the AUC to 0.896(95% CI: 0.835-0.976).CONCLUSION: Baseline ocular parameters, including central corneal thickness and pupil diameter, in patients with T2DM can be used to predict the risk of developing diabetic retinopathy.