['To investigate the risk factors associated with suprachoroidal hemorrhage (SCH) during vitrectomy.', 'Of 6971 pars plana vitrectomies performed between May 1988 and December 1994, SCH occurred intraoperatively in 12 (0.17%) cases. Forty-two age- and sex-matched control subjects were selected by computer-generated random numbers. Preoperative and intraoperative variables were subjected to univariate and conditional logistic regression analysis.', 'Statistically significant risk factors for SCH after univariate analysis included myopia (P = .048), aphakia or pseudophakia (P = .024), rhegmatogenous retinal detachment (P = .044), scleral buckling and/or encirclage at vitrectomy (P = .029), and longer duration of surgery (P = .044). Multivariate analysis revealed independent risks associated with the absence of a lens and longer duration of the surgery.'] Do a case-control study of suprachoroidal hemorrhage during pars plana vitrectomy?