Changes in the nerve fiber layer thickness following a reduction of intraocular pressure after trabeculectomy

Purpose: To assess changes in the nerve fiber layer thickness after trabecu lectomy using scanning laser polarimetry. Methods: The authors prospectively enrolled 46 eyes from 46 patients with p rimary open-angle glaucoma in whom intraocular pressure had been reduced by more than 30% after trabeculectomy without significant: ophthalmic complic ations and from whom good quality images were obtained by a scanning laser polarimetry preoperatively and at 3 to 6 months after trabeculectomy. In ea ch enrolled eye, changes in the nerve fiber layer thickness after surgery i n the defined ring (1.8 disc diameters) around the optic disc were calculat ed in 10 degrees intervals (36 sectors in total) and in the following 4 qua drants (the sum of 9 10 degrees sectors): superior, nasal, inferior, and te mporal. Results: The mean intraocular pressure was 22.6 +/- 6.9 mm Hg preoperativel y and 10.2 +/- 3.7 mm Hg postoperatively (P < 0.01). According to the analy ses in every 10 degrees, the postoperative nerve fiber layer thickness was significantly greater than the preoperative nerve fiber layer thickness in the superotemporal region (10-50 degrees) and inferotemporal region (290-34 0 degrees) of the optic disc (P < 0.05). A stepwise multiple regression ana lysis showed that only the preoperative mean deviation in the Humphrey visu al fields was a significant independent factor associated with changes in t he nerve fiber layer thickness in the nasal and inferior quadrants. Conclusions: The thickness of the nerve fiber layer, as measured by scannin g laser polarimetry, may increase after trabeculectomy, especially in the s uperotemporal and inferotemporal regions, and can be expected in cases in t he early stage of glaucoma that have a better mean deviation.