BackgroundWe classified iatrogenic retinal break formation during 20-gauge pars plana vitrectomy for proliferative diabetic retinopathy into three types according to the mechanism of development, and evaluated the association of each type with postoperative complications. This is the largest series of such patients published to date.MethodsThis was a retrospective comparative study of 760 eyes from 609 cases who underwent primary 20-gauge vitrectomy for proliferative diabetic retinopathy and were followed-up for at least 6 months after surgery. Postoperatively, the eyes were classified as having vitreous hemorrhage only (group 1), fibrovascular membrane without traction retinal detachment (group 2), or fibrovascular membrane with traction retinal detachment (group 3).ResultsThe overall incidence of iatrogenic retinal breaks was 29%. Fibrovascular membrane dissection was associated with retinal break formation in 50 of the eyes in group 3, an incidence which was significantly higher than that in group 2 (P < 0.001). Posterior vitreous detachment creation and peripheral vitreous shaving were associated with retinal break formation in 8% of eyes overall, and oral dialysis occurred in 2%. Postoperatively, vitreous hemorrhage requiring washout, neovascular glaucoma, recurrent retinal detachments, and fibrovascular proliferation at the sclerotomy sites occurred in 4%, 4%, 3%, and 1%, respectively, of all eyes. Outcomes of eyes with these postoperative complications, other than vitreous hemorrhage, were poor. Multiple regression analysis revealed retinal break formation during fibrovascular membrane dissection to be significantly related to postoperative vitreous hemorrhage (P = 0.019), recurrent retinal detachments (P < 0.001), and neovascular glaucoma (P = 0.048). Oral dialysis was also significantly related to postoperative vitreous hemorrhage (P = 0.001).ConclusionIatrogenic retinal break formation during fibrovascular membrane dissection was more likely to be the cause of poor outcomes than peripheral retinal breaks or oral dialysis.