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

Abstract

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.

Keywords: external trabeculectomy; modified deep sclerectomy.

Figure 1

Mean IOP preoperatively and postoperatively in regular intervals during follow up in RDS and RDS and external trabeculectomy. Abbreviations: IOP, intraocular pressure; RDS, reversed deep sclerectomy.

Figure 2

Kaplan–Meier curves for over time effectiveness of RDS and RDS and external trabeculectomy. Abbreviation: RDS, reversed deep sclerectomy.