We compared the results of visual field examination obtained with a Humphrey 30-2 program between 57 eyes of 57 low-tension glaucoma (LTG) and 57 eyes of 57 primary open-angle glaucoma (POAG; max IOP > or = 25 mmHg) cases, whose mean deviation (MD) given by STATPAC was > -10 dB. MD, age, and refraction showed no differences between the two groups. Corrected pattern standard deviation (CPSD) was significantly higher in the LTG group (p < 0.01). The total deviation (TD), deviation from the age-corrected normal reference, was found to be significantly lower by about 5 dB in the LTG group at two test points nasal-superior to the fixation point (Wilcoxon rank sum test, p < 0.01). Logistic discriminant analysis carried out to exclude a subtle difference in the distribution of the stage of disease between the two groups confirmed a significant between-group difference at the above-mentioned points. Furthermore, to compare the unevenness of visual field in the two groups, [TD-mean TD] was calculated, where mean TD was the average of 70 points of TD excluding the uppermost four points, and the same two points obtained above were found to decrease significantly in LTG, while all points were diffusely damaged in POAG. These results may imply a difference in the mechanism of visual field damage between LTG and POAG.