To study the differences in protein profiles before and after intravitreal ranibizumab (IVR) treatment, 12 vitreous humor (VH) samples were collected from 6 proliferative diabetic retinopathy (PDR) patients before (pre group) and after IVR treatment (post group). LC–MS/MS and bioinformatics analysis were performed to identify differentially expressed proteins.Targeted proteins were validated by parallel reaction monitoring (PRM).