Bevacizumab Pretreatment and Long Acting Gas Infusion on the Vitreous Clear-up After Diabetic Vitrectomy

From December 2006 to August 2007, consecutive patients undergoing primary pars plana vitrectomy for active proliferative diabetic retinopathy were recruited for the prospective study. Included cases should have active fibrovascular proliferation with vitreo-retinal adhesions in 3 or more sites but not extending beyond equator in more than one quadrant. Active fibrovascular proliferation is defined as visible new vessels within the proliferative membranes with any degree of fresh vitreous or preretinal hemorrhage. Exclusion criteria are: 1. History of preoperative or postoperative anticoagulant therapy; 2. History of blood diseases associated with abnormal coagulation; 3. Severe proliferation with anticipation of silicone oil usage. Informed consent is obtained in every patient before surgery. The protocol was approved by the review board and research ethics committee of National Taiwan University Hospital.

All cases in the study group are prospectively enrolled (group 1). Consecutive patients fulfilling the enrollment criteria receive intravitreal bevacizumab (1.25mg in 0.05ml) injection 7 to 9 days before surgery and intravitreal 10% C3F8 infusion at the end of surgery. The surgical outcomes are compared with a non-concurrent control group that received gas infusion only (group2). The control group is matched by baseline characteristics and the severity of diabetic proliferation with the study group. The comparisons between the two groups are possible because all the relevant parameters have been carefully documented in the control group. A single surgeon (CMY) performed all of the operations.

Operative Technique For intravitreal bevacizumab injection, after topical anesthesia, patients were disinfected three times with povidone-iodine solution and draped. After eyelid speculum put in place, the eyes are further anesthetized with proparacaine -soaked cotton-tip applicators. Bevacizumab (1.25mg in 0.05ml) is drawn into a 1 ml syringe through a 27-gauged needle from a newly opened vial and injected through a 30-gauged needle into the vitreous cavity via temporal lower pars plana. Anterior chamber paracentesis is not performed.

Standard 3-port pars plana vitrectomy as described previously is done in every case. In short, vitreoretinal traction, fibrovascular tissues, and opacified vitreous as well as blood clots adherent to the peripheral vitreous skirt are removed as completely and safely as possible. Hemostasis is obtained by raising the infusion bottle, mechanical compression using a soft-tipped cannula, endodiathermy, or a combination of the above techniques. Blood clots formed during tissue dissection are removed carefully except on the bleeding sites where they were trimmed to small islands. Panretinal photocoagulation in non-laser treated eyes or supplementary laser in previously laser-treated eyes extending beyond the level of the equator is performed. Further peripheral retinal cryotherapy (10 to 12 spots in one row) is done. 10% C3F8 intravitreal infusion is done in each case before wound closure. Finally, cryotherapy of the sclerotomy sites (1 spot, each 6 seconds, for 3 sclerotomy sites) is performed.

After surgery, all patients are kept in a prone position overnight, and maintained a head-down position during waking hours. The patients are then allowed to lie on either side during sleep for 3 weeks thereafter. Ophthalmological examinations are performed in the first 4 days after surgery, then weekly for 4 weeks, biweekly for 1 month, and then monthly for at least 6 months.