Optic nerve head surface depression in patients with glaucoma has been previously reported. We quantitatively compared the mean optic disc cup surface depth between glaucoma-like disc (GLD) patients with large cup-to-disc ratios and primary open-angle glaucoma (POAG) patients.

A total of 40 eyes of 40 patients with GLD and 40 eyes of 40 patients with POAG were included in this study. All patients had an average cup-to-disc ratio of 0.7–0.8. The optic disc area, mean cup-to-disc ratio, and mean optic disc cup volume were measured using spectral domain optical coherence tomography (Cirrus™ HD-OCT; Carl Zeiss Meditec, Inc., Dublin, CA, USA). The mean optic disc cup surface depth was calculated using the formula: (mean optic disc cup volume/[optic disc area × mean cup-to-disc ratio²]) − 200 µm.

The mean ages of patients were 61.18 ± 11.83 and 59.65 ± 11.69 years for the GLD and POAG groups, respectively. The average cup-to-disc ratios were 0.74 ± 0.03 and 0.75 ± 0.03 for the GLD and POAG groups, respectively, but no significant difference was observed between the two groups. The mean optic disc cup surface depths were 144.74 ± 82.78 µm and 199.53 ± 90.26 µm for the GLD and POAG groups, respectively, and the difference between the two groups was statistically significant ( p = 0.006, t -test).

POAG patients showed a significantly greater mean optic disc cup surface depth compared to GLD patients with a similar mean cup-to-disc ratio. Based on the results of spectral domain optical coherence tomography, confirming the mean optic disc cup surface depth is expected to provide additional information to distinguish GLD from POAG patients.