Reduction in dose of intravitreous bevacizumab before vitrectomy for proliferative diabetic retinopathy.

B evacizumab (Avastin) is a full-length recombinant humanized monoclonal antibody directed against vascular endothelial growth factor (VEGF). It has been approved by the US Food and Drug Administration for the treatment of metastatic colorectal cancer. Intravitreous (IV) injection of bevacizumab, 1.25 mg/0.05 mL, has been studied in patients with age-related macular degeneration, macular edema associated with retinal vein occlusion, and diabetic macular edema. Recently, bevacizumab administered prior to vitrectomy for proliferative diabetic retinopathy (PDR) was reported to reduce intraoperative bleeding. Sawada et al showed that IV bevacizumab blocked all free VEGF in the aqueous humor. However, IV bevacizumab may cause systemic adverse effects such as thromboembolic diseases or increases in systolic blood pressure. Moreover, the rapid progression of traction retinal detachment after IV injection of bevacizumab was reported. Therefore, we need to consider an appropriate dose of bevacizumab to be injected intravitreally. The purpose of this study is to elucidate whether a reduced dose (0.25 mg) of IV bevacizumab has an effect equally strong as the widely administered dose (1.25 mg) when IV bevacizumab is used as a surgical adjunct to treat PDR.