Prospectively, 28 eyes of 23 patients undergoing trabeculectomy were divided into two groups. The first group received a large scleral flap (4 mm X 4 mm X 4 mm) and corneal block (3 mm X 3 mm). The second group received a small scleral flap (2 mm X 2 mm X 2 mm) and corneal block (1 mm X 1 mm). No other changes in technique were made. After a mean follow-up of 13 months, there was no significant difference in final intraocular pressure, visual acuity, or complication rates between groups.