AIM: To assess and compare the diurnal macular choroidal area fluctuation in normal and primary open angle glaucoma (POAG) groups using enhanced depth imaging optical coherence tomography (EDI-OCT). METHODS: Twenty-eight normal and 27 POAG eyes were enrolled in this study. EDI-OCT was used to measure the macular choroidal area every 3h from 9: 00 a.m. to 21:00 p.m. RESULTS: Significant diurnal fluctuations of macular choroidal area were observed in both normal (P=0.003) and POAG groups (P<0.001). But no significant macular choroidal area difference has been found between the two groups at all the five measurement time-points (512778 +/- 166242 vs 455079 +/- 207278 mu m(2), P=0.195 at 9: 00 a. m.; 501526 +/- 168953 vs 447846 +/- 211147 mu m(2), P=0.245 at 12:00 a.m.; 501982 +/- 173158 vs 448024 +/- 206653 mu m(2), P=0.239 at 15:00 p.m.; 508912 +/- 174589 vs 457783 +/- 207081 mu m(2), P=0.252 at 18:00 p.m.; 503787 +/- 171241 vs 453230 +/- 205955 mu m(2), P=0.274 at 21:00 p.m.; respectively). Furthermore, neither the fluctuation manners nor the change in macular choroidal area between the two adjacent measurement time points showed significant difference between normal and POAG groups (all P>0.05). In the meantime, significant diurnal intraocular pressure fluctuations were also observed in normal and POAG groups (both P<0.001). CONCLUSION: In diurnal time, the macular choroidal area in both normal and POAG groups fluctuated significantly; moreover, neither the value of macular choroidal area, nor the fluctuation of macular choroidal area in POAG group is significantly different from that in normal group.