Interocular symmetry and intermachine reproducibility measured by two different models of Cirrus optical coherence tomography

Abstract

Abstract Background: Optical coherence tomography (OCT) is a non-invasive, sensitive and reliable method to measure retinal axonal and neuronal changes quantitatively at a few micrometers. Spectral-domain high definition OCT (HD-OCT) has been used globally and upgraded over the years several times Objective: This prospective study aims to compare interocular symmetry of the optic disc and macular data measured by Cirrus HD-OCT 4000 and HD-OCT 5000; to determine the intermachine reproducibility of the data from healthy subjects examined at the same visit by both HD-OCT models. Materials and Methods: Forty-three volunteers were recruited for this study. Participants were examined with both HD-OCT 4000 and HD-OCT 5000 at the same visit. Data of optic nerve head (ONH) were acquired using ONH Cube 200 x 200 scans. Macular data were acquired using macular volume cube 512 x 128 scans. Results: The average age of the participants was 33 ± 8.6 years. Interocular OCT parameters of ONH and macula were highly correlated between the right and left eyes regardless of HD-OCT 4000 or 5000. The average retinal nerve fiber layer (RNFL) thickness was thicker (96.67±11.19µm vs. 95.3±10.89µm, p<0.01), but average central subfield thickness (261.51±17.45µm vs. 262.51±17.39 µm, p<0.01) and average cube thickness (283.91± 13.59 µm vs. 286.55±13.09 µm, p<0.05) were thinner as measured by HD-OCT 4000 than by HD-OCT 5000. Intermachine reproducibility and reliability of the macular parameters and RNFL are good with high intraclass correlation coefficient (ICC) and low coefficient of variation (CV). Ganglion cell-inner plexiform layer (GCIPL) in the macula measured by two OCT models was close to each other with an average thickness of 85 µm and had high intermachine reproducibility with high ICC (0.993) and low CV (1.2%). Conclusion: The interocular symmetry from both HD-OCT models was high. Intermachine reproducibility for RNFL and all macular parameters was also high. GCIPL has small intermachine differences and high reproducibility with perfect reliability. The results imply that GCIPL values measured by two HD-OCT models maybe used interchangeably.