Risk factors for normal-tension glaucoma among subgroups of patients.

OBJECTIVE To identify risk factors for normal-tension glaucoma among subgroups of patients. METHODS In 93 patients with unilateral normal-tension glaucoma, intereye comparison of baseline spherical equivalent, central corneal thickness, untreated intraocular pressure, disc area, and zone beta variables was performed among the following 4 subgroups classified according to age and visual field pattern standard deviation of the eye with glaucoma: subgroup 1 (age < or = 50 years and visual field pattern standard deviation < or = 8 dB), subgroup 2 (< or = 50 years and >8 dB), subgroup 3 (>50 years and < or = 8 dB), and subgroup 4 (>50 years and >8 dB). RESULTS Fourteen, 27, 30, and 22 patients were included in subgroups 1, 2, 3, and 4, respectively. The untreated intraocular pressure in subgroup 1 (P = .005), the zone beta variables in subgroup 2 (P < .001), and both the untreated intraocular pressure (P = .010 and P = .034, respectively) and the zone beta variables (P < or = .008 and P < or = .006, respectively) in subgroups 3 and 4 were significantly greater in the eyes with glaucoma than in the normal contralateral eyes (by paired t test or Wilcoxon signed rank test). The other variables showed no significant difference between the eyes in any subgroup. CONCLUSION The zone beta variables (and not the untreated intraocular pressure) may represent significant risk factors in young patients having normal-tension glaucoma with moderate to severe visual field loss.