Quantitative differences between the optic nerve head and peripapillary retina in low-tension and high-tension primary open-angle glaucoma.

PURPOSE: To determine whether quantitative differences in optic nerve topography could be identified between patients having primary open-angle glaucoma with normal intraocular pressure (low-tension primary open-angle glaucoma [LT-POAG]) vs those with elevated intraocular pressure (high-tension primary open-angle glaucoma [HT-POAG]).

METHODS

We attempted to match 31 eyes of 31 patients in the LT-POAG group on a case-by-case basis with comparable eyes of 31 patients with HT-POAG. We used the Heidelberg Retina Tomograph to evaluate the optic nerve head and retinal nerve fiber layer.

RESULTS

Cup areas and cup:disk area ratios were significantly larger (P < .05), whereas rim areas, rim volumes, retinal nerve fiber layer heights, and retinal nerve fiber layer cross-sectional areas were consistently smaller, but not significantly so (P > .05), in the LT-POAG group. The inferior neuroretinal rim area was significantly smaller (P < .05) and the mean deviation of superior arcuate area was significantly greater than the opposite sector in patients with LT-POAG but not in those with HT-POAG. A relationship between localized measurements of the optic nerve head and mean deviation was more apparent in the LT-POAG group than in the HT-POAG group.

CONCLUSIONS

The optic cups were larger in patients with LT-POAG than in those with HT-POAG. Measurements of sectors of the optic disk correlated better with visual field changes in LT-POAG than did global measurements of the whole nerve head, indicating more vulnerability of the optic nerve to focal damage with low intraocular pressure.