A variety of visual field indices were studied with Octopus peridata with the use of Octopus 201 and its examination program No. 31 in 31 eyes of 31 normal tension glaucoma (NTG) cases that showed mild to moderate degree of glaucomatous visual field defects. Twelve eyes of 12 normal volunteers served as the controls. On the basis of the results of clinical tests for intra-ocular pressure (IOP) dynamics including C-value, diurnal variation of IOP and IOP rise after the water drinking test, 31 NTG eyes were divided into 17 positive response eyes and 14 negative response eyes by the clinical tests. Though significant difference (p < .0001) of the value in visual field indices was found between NTG eyes and control eyes, no significant difference was observed between positive and negative response eyes of NTG. The value of global short-term fluctuation in positive response eyes (2.1 +/- 0.9 dB), however, appeared to be significantly (p < .004) greater than that in negative response eyes (1.3 +/- 0.4 dB) and control eyes (1.3 +/- 0.4 dB).