Abstract
Purpose: :
The clinical utility of the new OCT instruments depend strongly on the reproducibility of its measurements. Reproducibility is expected to be improved because of greater rapidity of scan acquisition, which avoid movement artefacts. Aim of the study was to assess retinal nerve fiber layer (RNFL) thickness reproducibility using 6 different spectral-domain OCTs (SD-OCT) and one time-domain OCT.
Methods: :
RNFL thickness (average and 4 quadrants values) of 6 SD-OCTs (Spectral OCT/SLO Opko/OTI, 3D-OCT 2000 Topcon, Nidek RS-3000, Cirrus HD-OCT Zeiss, RTVue-100 Optovue and Spectralis HRA+OCT Heidelberg) and 1 time-domain OCT (Stratus OCT Zeiss) was measured in 38 randomly chosen, consecutive eyes of healthy volunteers by 2 masked operators:A (L.P.), B (M.G.) using the 7 OCT devices. Exclusion criteria were: history of intraocular surgery, retinal diseases, glaucoma, refractive error more than ± 2 dioptres. Both observers repeated two consecutive measurements in one eye (RE) of each patient during the same day. Inter-observer and intra-observer variability was evaluated by Bland-Altman analysis. Instruments-to-instrument reproducibility was determined by ANOVA for repeated measures with two within factors (instrument-operator); post hoc test for differences among instruments was also evaluated.
Results: :
Mean RNFL average thickness ranged from 90.08 µm to 106,51 µm. Cirrus HD-OCT and Spectralis HRA+OCT Heidelberg showed the thinner RNFL values in all measurements; 3DOCT 2000 the highest. Bland-Altman plots showed variable inter- and intra-operator agreement depending on the instruments. Spectralis HRA+OCT Heidelberg demonstrated the best inter- and intra-operator agreement for average RNFL thickness (95% limits of agreement -5,7 to 4,8 inter-operator; -4,2 to 4,1 intra-operator for operator B), RTVue-100 Optovue the worst (95% limits of agreement -17,2 to 11,4 inter-operator; -13,4 to 10,9 intra-operator for operator B). In each quadrant we observed the same tendency.
Conclusions: :
Heidelberg Spectralis demonstrated thinner RNFL measurments and higher agreement. RNFL measurements obtained by the SDOCT devices indicate that these measurements are not interchangeable in clinical evaluation.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • nerve fiber layer • optic disc