Glaucoma surgery decreases the rates of localized and global visual field progression

Abstract

Purpose: Incisional glaucoma surgical procedures produce greater intraocular pressure (IOP) reduction and less IOP variability than medical treatment. We sought to determine the efficacy of glaucoma surgery in decreasing localized and global rates of visual field (VF) progression.

Design: Retrospective, interventional case series.

Methods: Subjects in the New York Glaucoma Progression Study with glaucomatous optic neuropathy, repeatable VF loss, and 10 or more Swedish interactive threshold algorithm standard VF examinations were assessed for eligibility. Patients who underwent successful glaucoma surgery (not requiring further surgical intervention and IOP < 18 mm Hg) in either eye and who were followed up for at least 2 years before and after surgery were enrolled. Automated pointwise linear regression analysis was used to calculate global and localized rates of progression before and after surgery. Eyes with other ocular conditions likely to affect the VF and an insufficient number of VF to create a slope before and after surgery were excluded. Comparisons were performed within the same eyes before and after surgery (Student paired t test).

Results: We enrolled 28 eyes of 28 patients (mean age, 61.2 +/- 14.5 years). The mean number +/- standard deviation of VF was 13.4 +/- 2.3, spanning 7.1 +/- 1.2 years (range, 4 to 9 years). Mean IOP +/- standard deviation decreased from 19.0 +/- 3.9 mm Hg before surgery to 11.3 +/- 3.7 mm Hg after surgery (40% reduction; P < .01). Mean global progression rates decreased from -1.48 +/- 1.4 dB/year before surgery to -0.43 +/- 0.8 dB/year after surgery (70% reduction; P = .01). Twelve eyes (42.8%) had at least 1 significantly progressing point before surgery, whereas only 2 (7.1%) had at least 1 progressing point after surgery. Each 1 mm Hg of IOP reduction after surgery resulted in a 0.1 dB/year decrease in the global rate of progression.

Conclusions: Successful IOP reduction after glaucoma surgery greatly reduces both the number of progressing points and the localized and general rates of VF progression.