Anisometropia and degree of optic nerve damage in chronic open-angle glaucoma

To address the question of whether the refractive error plays a role in the amount of optic nerve damage in glaucoma, we intraindividually compared inter-eye differences in refractive error with inter-eye differences in parameters indicating the degree of glaucomatous optic nerve damage, and we interindividually correlated refractive error with neuroretinal rim area and visual field loss.

Comparative clinical observational study.

This comparative clinical observational study was conducted in a university eye hospital. The study included 1,444 eyes of 876 patients with primary or secondary chronic open-angle glaucoma. Patients with a highly myopic refractive error (> or = -8 diopters) were excluded, owing to differences in the anatomy of the optic nerve head. Color stereo optic disk photographs were taken and morphometrically evaluated. The main outcome measures were refractive error, neuroretinal rim area, horizontal and vertical cup/disk diameter ratios, and visual field loss.

In an interindividual statistical analysis, area of neuroretinal rim, horizontal and vertical cup/disk diameter ratios, and mean visual field loss were not significantly (P >.10) correlated with refractive error. In an intraindividual comparison, inter-eye differences in refractive error were not significantly (P >.05) correlated with inter-eye differences in neuroretinal rim area and mean visual field defect. The eye with the more myopic refractive error and the contralateral eye with the less myopic refractive error did not vary significantly in neuroretinal rim area and mean visual field defect.

For nonhighly myopic (< -8 diopters) patients with primary or secondary chronic open-angle glaucoma, the refractive error may not play a major role for the amount of glaucomatous optic neuropathy. For nonhighly myopic (< -8 diopters) patients with primary or secondary chronic open-angle glaucoma, myopia may not be an important risk factor for glaucoma.