Intra and interoperator reproducibility of retinal nerve fibre and macular thickness measurements using Cirrus Fourier-domain OCT

Abstract

Purpose: To test intrasession, intersession, intervisit and interoperator reproducibility of retinal nerve fibre (RNFL) measurements and retinal thickness in healthy subjects using Cirrus Fourier-domain optical coherence tomography (OCT) (Carl Zeiss Meditec, Inc).

Methods: Seventy-two eyes of 72 healthy subjects were included in the study. All the eyes underwent three 512 × 128 volume cube centred on the fovea and three 360° circular scans centred on the optic disc by one observer. This sequence was redone by another observer on a second visit within a 2-week period. Descriptive statistics, analysis of variance, intraclass correlation coefficients (ICCs) and coefficients of variation (COVs) were calculated for the nine areas corresponding to the Early Treatment Diabetic Retinopathy Study and for quadrants and RNFL clock hr sectors.

Results: Retinal thickness and RNFL measurements were highly reproducible. Mean total retinal thickness was 285.2 ± 15.3 μm by observer 1 and 284.2 ± 12.9 μm by observer 2. Mean COV was 1.2%. Mean RNFL average thicknesses were 96.0 ± 7.7 and 95.7 ± 7.9 μm by observer 1 and 2, respectively. Mean COV was 4.4%. The ICCs ranged from 0.823 to 0.992. Mean differences between both operators were lower than 3 μm, and no significant differences were found.

Conclusions: Retinal and RNFL thickness measurements obtained using Cirrus OCT show good repeatability for healthy eyes and few differences between intra- and interobserver evaluations. It can be considered a valid device for measuring retinal and optic nerve parameters in normal eyes.