Effect of trabeculectomy on visual field in progressive normal-tension glaucoma

The purpose of this study was to investigate the effectiveness of surgical treatment on the visual field in normal-tension glaucoma (NTG) eyes, and associated factors for visual field progression. Thirty-two patients (32 eyes) were enrolled in this retrospective study. Stepwise regression analysis was performed to correlate the visual field change with several clinical factors, such as intraocular pressure (IOP), and several IOP-unrelated parameters. Surgical reduction of IOP helps in preventing the progression of visual field damage in NTG eyes. The stepwise analysis revealed that better visual field prognosis was associated with higher preoperative IOP (P = 0.006) and the absence of diabetes mellitus (P = 0.04). The functional outcome in the lower IOP group was better when the patients were using Ca2+-channel blockers (P = 0.08); it was worse if disc hemorrhage appeared (P = 0.02). In conclusion, both IOP-related and unrelated factors are associated with visual field damage progression in NTG eyes. The functional prognosis in the eyes with low IOP depends on IOP-unrelated factors.