Panretinal photocoagulation versus intravitreal injection of bevacizumab as a preoperative adjuvant before vitrectomy in the management of proliferative diabetic retinopathy

Abstract

Background Proliferative diabetic retinopathy (PDR) characterized by neovascularization of the optic disk, retina, and/or iris may be an aberrant attempt to alleviate hypoxia in eyes with severe capillary closure or other retinal ischemia. The new vessels grow perpendicular to the plane of the retina into the scaffolding provided by the vitreous cortex, typically from venules at the junction of the perfused and nonperfused retina. Objective This work aims to study the effect of panretinal photocoagulation (PRP) versus intravitreal injection of bevacizumab (Avastin) before vitrectomy in the management of PDR. Patients and methods Our clinical study was conducted on 60 eyes in 40 patients with PDR with indications of vitrectomy (vitreous hemorrhage, tractional retinal detachment involving or threatening the macula, combined tractional/rhegmatogenous retinal detachment and fibrovascular membranes covering and distorting the macula, persistent macular edema with viteromacular traction) managed by parsplana vitrectomy after preoperative preparation by intravitreal injection of bevacizumab (Avastin) or PRP used as an adjunct was grouped into two groups: group A and group B; FFA was done previtrectomy for all cases. Results Intraoperative using of endodiathermy is reported as once in eight cases, twice in 15 cases, three times in seven cases in group A, while once in 14 cases, twice in six cases, and not used in 10 cases in group B. Intraoperative use of endolaser is reported as less than 1500 shoots in seven cases, and more than 1500 shoots in 23 cases in group A, while less than 1500 shoots in 29 cases, and more than 1500 shoots in one case in group B. Therefore, bevacizumab or PRP induces regression of active fibrovascular proliferation decreasing the extent of bleeding during tissue segmentation and delamination. The lesser intraoperative bleeding makes visualization of the surgical plane better, which in turn facilitates a precise separation of the proliferative tissue from the retina and helps avoid accidental retinal vascular damage and iatrogenic retinal breaks and make the surgery and the results better than conventional surgery (without using any adjuvants). Conclusion Use of both adjuvants before vitrectomy enhances the outcome of vitrectomy when best indicated rather than without using. The shorter time of surgery and less use of endodiathermy or endolaser is with the PRP group, although postoperative best-corrected visual acuity gaining is not significant. So, accurate clinical differences between two adjuvants need more researches.