Background/aims: To evaluate to what extent the optic nerve head (ONH) parameters as measured with Heidelberg Retina Tomograph (HRT) differed from those measured with optical coherence tomography (OCT) in eyes with compressive optic neuropathy (CON) that had band atrophy (BA) of the optic disc.
Methods: A total of 30 eyes from 19 patients with BA due to chiasmal tumor and 162 eyes from 162 normal subjects were examined with HRT and Stratus OCT using the fast optic nerve scan protocol. Parameters measured by the two devices, including the disc area, cup/disc (C/D) area ratio, cup area, cup volume, rim area, and rim volume, were compared between the eyes of BA patients and controls. Bland-Altman plots were used to evaluate agreement for each parameter between OCT and HRT in both groups of eyes. Inter-method discrepancy of the measurements for each parameter was compared between the two groups of eyes.
Results: Eyes with BA had smaller cup and larger rim parameters than control eyes when measured with HRT, whereas they had significantly larger cup and significantly smaller rim parameters than control eyes when measured with OCT. HRT measurements tended to be consistently lower in the C/D area ratio and cup area and higher in the rim area and rim volume than OCT measurements for both control eyes and eyes with BA. The inter-method discrepancy for all the parameters except the disc area was significantly larger in eyes with BA than in control eyes.
Conclusion: The increased optic disc excavation was detected with OCT but not with HRT in CON eyes with BA of the optic disc. Thus, the distinct algorithms used by these two modalities affected the measurements of ONH parameters, particularly when assessing optic discs with temporal rim thinning.