Comparison of disc analysis algorithms provided by cirrus OCT and stereo optic-disc photography in normal and open angle glaucoma patients

Abstract

Purpose: To compare optic nerve head (ONH) parameters obtained by semi-automated disc analysis of stereo optic-disc photography (ODP) with those by spectral domain optical coherence tomography (SD-OCT) regarding their reproducibility, agreement and relationship with the retinal nerve fiber layer (RNFL) thickness.

Patients and methods: In this cross-sectional retrospective study, 91 eyes (50 normal and 41 with open angle glaucoma) from 47 patients were examined. ONH parameters were obtained by ODP and SD-OCT. Agreement and reproducibility were assessed by intra-class correlation coefficients (ICCs). Inter-device agreement and precision were also evaluated. The structural factors related to the ONH measurements by both instruments and the disparity between the measurements were evaluated by the generalized estimating equation model.

Results: ODP showed good intra-reader and inter-reader reproducibility, comparable to that of SD-OCT (ICC: >0.970). Disc area (DA) (ICC: 0.950) showed better inter-device agreement than rim area (RA) (ICC: 0.859). RNFL thickness was correlated with RA, but not with DA, for both devices. SD-OCT RA showed significant correlation with RNFL thickness in both the normal and glaucoma groups, whereas ODP RA correlated with RNFL only in the glaucoma group. The measurement disparity between the devices was influenced by the DA in both groups. The inter-device difference in RA was not correlated with RA, but instead with the RNFL thickness in the glaucoma group.

Conclusion: ONH parameters obtained by semi-automated algorithms of ODP showed excellent reproducibility and good agreement with those measured by SD-OCT. SD-OCT RA was a better indicator of RNFL thickness, compared with ODP RA for both normal patients and glaucoma patients; however, the inter-device disparity of the RA was less in glaucoma patients who had a thinner RNFL.