The severity of intraoperative bleeding, the extent of immediate postoperative preretinal blood, reabsorption time of blood around the disc area, total reabsorption time of preretinal blood, the rate and treatment of recurrent vitreous hemorrhage, and the change of best-corrected visual acuity will be compared between groups 1 and 2. Visual acuity will be graded into three levels: low (≤1 meter counting fingers), moderate (>1 meter counting fingers, but < 20/200), and good (≥ 20/200).