Nonpenetrating filtration surgery for glaucoma: control by surgery only

To report on intraocular pressure (IOP) control by nonpenetrating filtration surgery without medical treatment in eyes with primary open-angle glaucoma (POAG).

Oxford Eye Center and St. John Eye Hospital, Johannesburg, South Africa.

This retrospective study evaluated IOP control by nonpenetrating filtration surgery in 46 patients (86 eyes) with POAG who had surgery between February 1992 and February 1998 (mean follow-up 46 months); 48 eyes were previously treated, and 38 were newly diagnosed, untreated eyes. Under a trapezoidal scleral flap, a deep sclerectomy and a fenestration in Schlemm's canal were created without penetrating the anterior chamber. Postoperatively, when IOP rose above 20 mm Hg, instead of adding medical treatment, the filtration site was revised to re-establish filtration.

The mean drop in IOP was 50%, from a mean of 30.4 mm Hg preoperatively to a mean of 15.35 mm Hg postoperatively. After a mean period of successful filtration of 29.9 months, the filtration site was revised in 48 eyes (56%) to maintain the IOP below 21 mm Hg without medication. The reoperation rate was 4.7 times higher in previously treated patients than in untreated patients.

Nonpenetrating filtration surgery in eyes with POAG was more rewarding in untreated patients than in medically treated patients. To control IOP without medication, revision of the filtration site is feasible and needed in the medium and long term.