Comparison of Visual Field Progression Between Relatively Low and High Intraocular Pressure Groups in Normal Tension Glaucoma Patients

Purpose: To determine the risk factors of visual field (VF) progression in relatively low and high intraocular pressure (IOP) groups in normal tension glaucoma (NTG) patients and to compare progression rate of VF defects between the 2 groups. Methods: Forty-nine eyes of 49 NTG patients with untreated IOP of <= 15 mm Hg (group A) and 49 eyes of 49 NTG patients matched by age and baseline VF mean deviation (MD) who had untreated IOP of > 15 mm Hg (group B) were included in this retrospective chart review study. All patients were followed > 5 years. Risk factors for VF progression were evaluated using Cox proportional hazards models in each group, separately. Changes in VF indexes were compared between the 2 groups. Results: Mean IOP and IOP fluctuation were significantly greater in group B than in group A (P < 0.001 and P = 0.016), whereas other factors did not differ between the groups. In multivariable analysis, VF progression was significantly associated with disc hemorrhage in group A (HR, 6.19; P = 0.017) and mean IOP in group B (HR, 1.77; P = 0.029). There was no significant difference between the groups in incidence of progression and in changes of MD, pattern SD, and VF index (P = 0.942, 0.874, and 0.887, respectively). Conclusions: Although progression rate was similar, the risk factors for VF progression were different in the 2 groups. These findings may suggest that IOP-dependent and IOP-independent factors affect VF progression differently in the 2 groups.