The MVMR results showed that even after adjusting for other types of cathepsins, the association between Cathepsin H and PDR (OR = 1.0546, 95% CI = 1.0175–1.0931, P = 3.6 × 10− 3) (Fig. 4C) and diabetic maculopathy (OR = 1.0682, 95% CI = 1.0095–1.1304, P = 0.0222) (Fig. 4D) still showed a significant positive causal relationship. Here, CTSS is linked to diabetic maculopathy.