Appropriate timing schedule for intravitreal anti-VEGF injection as adjuvant therapy before pars-plana vitrectomy in proliferative diabetic retinopathy, a meta analysis

Background Many studies introduced intravitreal injections of anti-vascular endothelial growth factors (VEGFs) as a new strategy for safer and more convenient vitrectomy in patients with severe proliferative diabetic retinopathy (PDR). While possible side effects such as progression of vitreoretinal fibrosis should be kept in mind, these may be prevented by proper preoperative timing of injection.Research design and methods This study was conducted based on the systematic review guidelines in four steps: definition of search strategy, selecting and evaluating studies, checking inclusion and exclusion criteria, and statistical analysis. Eighteen clinical trials with a total sample size of 1165 patients were included. According to the timing of injection, patients were divided into three groups: injection 72 hours, injection 3–7 days, and injection 7–21 days before surgery.Results The lowest risk of intraoperative hemorrhage, the minimum duration of surgery and the lowest need for silicone oil (SO) tamponade was in the injection group 7–21 days before surgery. The rate of iatrogenic retinal break during surgery and the necessity for relaxing retinotomy in the injection group 72 hours before surgery was lower than the other two groups. However, there were limited data regarding the requirement of relaxing retinotomy, the need to inject SO, and the occurrence of iatrogenic retinal break.Conclusions This meta-analysis showed, to prevent tractional complications, it is recommended to inject within 3 days before surgery.