Effect of Myopia on the Progression of Primary Open-Angle Glaucoma

Abstract

PURPOSE. To evaluate the effect of myopia on the progression of primary open-angle glaucoma. METHODS. In this retrospective cohort study, eyes were classified into nonmyopic (NMG, >0 diopters [D]), mild to moderate (MMG, 0 to -6 D), and highly myopic glaucoma (HMG, < -6 D) groups according to the level of spherical equivalent. Glaucoma progression was determined either by optic disc/retinal nerve fiber layer (RNFL) photographs or by serial visual field (VF) data. Cox's proportional hazard models were used to detect associations between potential risk factors and glaucoma progression. RESULTS. Among 369 eyes from 369 glaucoma patients (average follow-up, 4.4 years), 54 of 178 eyes (30.3%) in the NMG, 49 of 151 eyes (32.5%) in the MMG, and 8 of 40 eyes (20.0%) in the HMG showed progression. When VF was used as a progression criterion, thinner baseline RNFL (hazard ratio [HR]: 0.942, P < 0.001) was predictive of progression. When optic disc/RNFL photographs were used, worse baseline visual field mean deviation (VF MD) and thinner RNFL were associated. The HMG category was a preventive factor for optic disc/RNFL photographic progression (HR: 0.323, P = 0.031). CONCLUSIONS. No levels of myopia were associated with glaucoma progression in our study. High myopia was a protective factor for optic disc/RNFL progression. These results may be interpreted as a lower progression detection rate because of the difficulty in detecting changes in the optic disc/RNFL in HMG, or as a consequence of some of highly myopic eyes that may not be true cases of glaucoma.