A modified deep sclerectomy with or without external trabeculectomy: a comparative study

PURPOSE: To determine whether the removal of the inner wall of Schlemm’s canal (external trabeculectomy) improves the effectiveness of a modified method of deep sclerectomy (DS), which we will call “reversed” deep sclerectomy (RDS). MATERIALS AND METHOD: We conducted a prospective study of two groups of patients. Group A included 22 eyes of 18 patients with open angle glaucoma (OAG) under maximum medical treatment, which underwent RDS – a modified method of performing DS – with the removal of the inner wall of Schlemm’s canal (external trabeculectomy) and without using any implant. Group B included 20 eyes of 17 patients which had undergone RDS alone. Demographic and tonometric data of patients of Group A revealed no significant difference from data of patients in Group B. A mean follow up period for Group A was 22.8 months and for Group B was 23.4 months. The outcome of the operations was termed a total success when intraocular pressure (IOP) was <21 mmHg postoperatively, without additional treatment, relative success when IOP was <21 mmHg with additional treatment and a total failure when IOP >21 mmHg with medical treatment. RESULTS: Total success was achieved in 18/22 eyes (81.8%) for Group A and in 8/20 eyes (40%) for Group B (P < 0.05). Relative success was achieved in 22/22 (100%) for Group A and in 17/20 eyes (85%) in Group B (P = NS). Total failure occurred in 0/22 eyes (0%) in Group A and in 3/20 (15%) eyes in Group B (P = NS). The mean postoperative IOP in Group A was 13.5 ± 2.8 mmHg with a reduction of 12.4 ± 4.6 mmHg (48.1%) and in Group B mean postoperative IOP was 18 ± 4.3 mmHg with a reduction of 6.2 ± 6.9 (25.6%) (P < 0.001). Mean drug reduction postoperatively was 3.2 ± 0.9 drugs in Group A and 1.7 ± 1.2 in Group B (P < 0.001). CONCLUSION: In the follow up time during which the two groups were under study (12–36 months), the removal of the inner wall of Schlemm’s canal while performing RDS proves an important factor in improving its effectiveness.