Differences in optic discs in low-tension glaucoma patients with relatively low or high pressures.

We evaluated the differences in the optic nerve head in patients with chronic open-angle glaucoma (HTG) and those with low-tension glaucoma with either relatively high (between 16 and 21 mmHg [LTGH]) or low (< or = 15 mmHg [LTGL]) intraocular pressures. We included 36 patients in this study. We found that LTGL patients had a significantly greater mean area of peripapillary atrophy inferior to the optic disc (0.65 +/- 0.38 mm2) than LTGH (0.40 +/- 0.38 mm2) or HTG (0.34 +/- 0.25 mm2) patients (p < 0.005). No significant difference was found between groups for the area of the neural rim, optic disc, cup/pallor discrepancy, or peripapillary halo, or in the diameter of the largest artery or vein in the inferior and superior peripapillary area. This study raises the question of whether a separate mechanism of damage could exist at the optic disc in patients whose intraocular pressure is < or = 15 mmHg because of a greater extent of peripapillary atrophy than in patients with higher intraocular pressures.