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 β 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 ≤50 years and visual field pattern standard deviation ≤8 dB), subgroup 2 (≤50 years and >8 dB), subgroup 3 (>50 years and ≤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 β variables in subgroup 2 (P < .001), and both the untreated intraocular pressure (P = .010 and P = .034, respectively) and the zone β variables (P ≤ .008 and P ≤ .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 β 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.