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M. R. Horne, T. Callan, M. Durbin, T. Abunto; Inter-Visit and Inter-Instrument Variability for Cirrus HD-OCT Peripapillary Retinal Nerve Fiber Layer Thickness Measurements. Invest. Ophthalmol. Vis. Sci. 2008;49(13):4624.
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© ARVO (1962-2015); The Authors (2016-present)
To measure the reproducibility of retinal nerve fiber layer (RNFL) thickness measurements from Cirrus Optical Coherence Tomography (CirrusTM HDOCT), and to determine if inter-visit or inter-instrument variability contribute significantly to overall variance.
First, a single operator scanned one eye of fifteen (15) healthy subjects using the Cirrus HD-OCT (Carl Zeiss Meditec, Inc., Dublin, CA) Optic Disc 200x200 scan. Subjects were imaged twice per system during a single visit on five systems. Instrument order was randomized for each subject. Then, the same operator scanned one eye of seventeen (17) healthy subjects using the same Optic Disc 200x200 scan three times per visit on three different visits. All scans for both phases were acquired within one week. Seventeen (17) average thickness parameters were calculated, including the average around a circle at 1.73 mm from the optic disc, four quadrant averages and twelve clock-hour RNFL thickness averages. Analysis of variance (ANOVA) was performed on all parameters using a random effects model without interactions. Variance components were used to estimate the reproducibility.
Neither the inter-visit nor the inter-system component was statistically significant for any of the parameters. The reproducibility standard deviation (SD) of the average thickness was 1.4 µm. For the quadrants, the reproducibility SD was 2.9 µm Temporal, 5.1 µm Superior, 4.0 µm Nasal, and 4.1 µm Inferior. The clock-hour reproducibility SD ranged from 3.0 µm at 9 o’clock to 9.0 µm at 12 o’clock.
We observed no statistically significant inter-visit or inter-system variability. The small random component of variance observed in both experiments corresponds to a high degree of reproducibility for all parameters for Cirrus HDOCT peripapillary RNFL thickness measurements.
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