Purpose: Bevacizumab is a human monoclonal IgG1 antibody that blocks the action of vascular endothelial growth factor (VEGF). The purpose of this study was to determine the level of VEGF and pigment epithelium-derived factor (PEDF) in eyes with proliferative diabetic retinopathy (PDR) before and after an intravitreal injection of bevacizumab.
Methods: Eleven eyes of ten patients were studied. Patients were included if they had neovascular glaucoma, rubeosis of the iris with PDR, or aggressive PDR. Samples of aqueous humor were collected just before the injection of bevacizumab and the vitrectomy. The concentrations of VEGF and PEDF in the aqueous humor were measured by enzyme-linked immunosorbent assay, and the effects of bevacizumab on PDR were evaluated.
Results: The free VEGF concentration before the injection was 676.5 +/- 186.7 pg/ml (mean +/- SEM, n = 11). Seven days later, it was significantly reduced to 7.1 +/- 7.1 pg/ml (P < 0.005, n = 9). The PEDF concentration before the injection was 2.32 +/- 0.49 microg/ml (n = 11), and 7 days later, it was 3.23 +/- 0.76 microg/ml (P = 0.33). During the vitrectomy, patients had less intraoperative bleeding when the neovascular tissues were cut.
Conclusions: An intravitreal injection of bevacizumab significantly decreased the free VEGF in the aqueous humor by 7 days, indicating that the clinical effects of bevacizumab appear rapidly. However, intravitreal bevacizumab did not affect the level of intraocular PEDF.