Optic nerve damage in highly myopic eyes with chronic open-angle glaucoma

PURPOSE. To compare the amount of optic nerve damage in relation to intraocular pressure in highly myopic eyes with chronic open-angle glaucoma versus non-highly myopic eyes with chronic open-angle glaucoma. METHODS. The comparative clinical observational study included 1841 eyes of 1100 patients with chronic open-angle glaucoma. The highly myopic study group consisted of 25 eyes with a myopic refractive error equal to or higher than -8 diopters. It was subdivided into eyes with an optic disc size larger than 2.7 mm(2) and eyes with an optic disc smaller than 2.7 mm(2). The control group included the remaining, non-highly myopic eyes (n = 1816). For all patients, a morphometric analysis of color stereo optic disc photographs was performed. Main outcome measures were morphometric optic disc measurements and intraocular pressure. RESULTS. In the highly myopic, large-optic-disc study group compared with the control group, maximal and minimal intraocular pressure readings were significantly (p < 0.05) lower and neuroretinal rim area corrected for optic disc size was slightly (p = 0.16) smaller. Comparing the total highly myopic study group with a control group adjusted for optic disc area, neuroretinal rim area was significantly (p = 0.039) smaller in the study group with no significant difference in intraocular pressure measurements between the groups. CONCLUSIONS. At a given intraocular pressure in chronic open-angle glaucoma, optic nerve damage may be more pronounced in highly myopic eyes with large optic discs than in non-highly myopic eyes. This may suggest a higher susceptibility for glaucomatous optic nerve fiber loss in highly myopic eyes than in non-highly myopic eyes.