It is known that the prevalence of normal tension glaucoma (NTG) or primary open angle glaucoma (POAG) is higher in the myopic population and that the prevalence of myopia and NTG is higher in Japan than in western countries. To evaluate the influence of myopic refractive error in the central 10 degrees of the visual field in NTG eyes, the data obtained from NTG eyes with the Humphrey Visual Field Analyzer were analyzed in comparison with data from POAG eyes. One hundred and twenty eyes of 86 NTG patients and 197 eyes of 138 POAG patients whose ages were 65 years or younger were included in this study. All of them had clear ocular media, refractive power less than +1.0 diopter and no myopic degeneration in the fundus. Multiple linear regression analysis was performed with the dependent variable of the deviation of the measured threshold value from the normal reference value (TD; STATPAC 2), and independent variables of myopic refractive power and the mean deviation (MD; STATPAC 2) as an index of the disease stage at each test point of the Humphrey 10-2 program and at the most central 12 test points of the 30-2 program. Myopic power was found to have a significant positive correlation with the depression in the lower cecocentral area in both NTG and POAG eyes, while only in NTG eyes it had a significant negative correlation with the depression in the upper arcuate area extending just nasal to the fixation point.