Long-term follow-up of visual field progression after trabeculectomy in progressive normal-tension glaucoma

OBJECTIVE: To evaluate the long-term effects of trabeculectomy on the progression of visual field damage in patients with progressive normal-tension glaucoma (NTG). DESIGN: Retrospective, noncomparative, interventional case series. PARTICIPANTS: Twenty-three patients with NTG who had significant progression of visual field damage preoperatively and underwent trabeculectomy using antimetabolites. METHODS: Visual field testing using the Humphrey Visual Field Analyzer was periodically performed before and for at least 5 years after surgery (mean, 6 years). The time course of the mean deviation (MD) and mean of total deviations (TD(mean)) in four separate subfields, superior and inferior cecocentral and superior and inferior arcuate fields, were analyzed using a linear mixed effects model. MAIN OUTCOME MEASURES: Intraocular pressure (IOP), preoperative and postoperative regression coefficients of the time course of MD or TD(mean) in the four subfields, corresponding to the rate of progression of visual field damage. RESULTS: IOP significantly decreased from 16.2 +/- 1.8 mmHg preoperatively to approximately 11 mmHg during the postoperative follow-up period (P < 0.001). The preoperative regression coefficient of MD change was significantly negative (-1.05 [95% confidence interval, -1.28 to -0.82] dB/year, P < 0.001). After surgery, it increased significantly to -0.44 (95% confidence interval, -0.64 to -0.24) dB/year (P < 0.001), but the postoperative value was still significantly negative (P < 0.001). In the superior cecocentral, superior and inferior arcuate fields, preoperative regression coefficients of TD(mean) change were significantly negative (P < 0.001) and significantly increased after surgery (P < 0.01). In the inferior cecocentral field, the preoperative regression coefficient was not significantly different from 0 (P = 0.72) and did not change significantly after surgery (P = 0.15). CONCLUSIONS: Trabeculectomy was statistically associated with slowing further progression of visual field damage in patients with progressive NTG. The progression, however, did not completely stop over the 6-year postoperative follow-up period.