Structure–function relationship among three types of spectral‐domain optical coherent tomography instruments in measuring parapapillary retinal nerve fibre layer thickness

Abstract

To compare the relationships of parapapillary retinal nerve fibre layer (RNFL) thickness among three spectral-domain optical coherence tomography (SD-OCT) instruments with visual field sensitivity (VFS). One hundred and thirteen eyes of 113 Japanese subjects with glaucoma (mean deviation in standard automated perimetry = -8.9 ± 6.7 dB) were imaged by Cirrus, RTVue and 3D OCT. The average hemi-superior and hemi-inferior RNFL thicknesses were obtained. In addition, the structure-function relationship using two retinotopic maps that consisted of six or nine sectors was also evaluated. Decibel (dB) scale and 1/Lamert (1/L) were used to express VFS. RNFL thickness correlation with corresponding VFS in visual field sectors was compared among the three instruments. Background RNFL thickness (non-neuronal tissue) for each instrument was estimated using a linear regression model at 1/L = 0. The correlation between the average hemi-superior and hemi-inferior RNFL thickness in the three SD-OCT instruments with corresponding VFS was similar. In the analysis of retinotopic maps, 3D OCT showed a higher correlation in superotemporal sectors than RTVue, whereas RTVue had a stronger relationship in the nasal sector than Cirrus. The background RNFL thickness extrapolated was approximately 60% that of normal eyes in all the instruments. The three SD-OCT showed similar overall correspondence with VFS with a partially discordant retinotopic relationship. RNFL measured with any SD-OCT devices likely contains non-neuronal tissue, comprising 60% of its thickness.