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Central Corneal Thickness Reproducibility among Ten Different Instruments

Pierro, Luisa; Iuliano, Lorenzo; Gagliardi, Marco; Ambrosi, Alessandro; Rama, Paolo; Bandello, Francesco

doi: 10.1097/OPX.0000000000000974
ORIGINAL ARTICLES
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Purpose To assess agreement between one ultrasonic (US) and nine optical instruments for the measurement of central corneal thickness (CCT), and to evaluate intra- and inter-operator reproducibility.

Methods In this observational cross-sectional study, two masked operators measured CCT thickness twice in 28 healthy eyes. We used seven spectral-domain optical coherence tomography (SD-OCT) devices, one time-domain OCT, one Scheimpflug camera, and one US-based instrument. Inter- and intra-operator reproducibility was evaluated by intraclass correlation coefficient (ICC), coefficient of variation (CV), and Bland-Altman test analysis. Instrument-to-instrument reproducibility was determined by ANOVA for repeated measurements. We also tested how the devices disagreed regarding systemic bias and random error using a structural equation model.

Results Mean CCT of all instruments ranged from 536 ± 42 μm to 577 ± 40 μm. An instrument-to-instrument correlation test showed high values among the 10 investigated devices (correlation coefficient range 0.852–0.995; p values <0.0001 in all cases). The highest correlation coefficient values were registered between 3D OCT-2000 Topcon—Spectral OCT/SLO Opko (0.995) and Cirrus HD-OCT Zeiss—RS-3000 Nidek (0.995), whereas the lowest were seen between SS-1000 CASIA and Spectral OCT/SLO Opko (0.852). ICC and CV showed excellent inter- and intra-operator reproducibility for all optic-based devices, except for the US-based device. Bland-Altman analysis demonstrated low mean biases between operators.

Conclusions Despite highlighting good intra- and inter-operator reproducibility, we found that a scale bias between instruments might interfere with thorough CCT monitoring. We suggest that optimal monitoring is achieved with the same operator and the same device.

*MD

PhD

Department of Ophthalmology, Vita-Salute University, San Raffaele Scientific Institute, Milan, Italy (LP, LI, MG, FB); Vita-Salute San Raffaele University, Milan, Italy (AA); and Cornea and Ocular Surface Unit, San Raffaele Scientific Institute, Milan, Italy (PR).

Luisa Pierro Department of Ophthalmology Vita-Salute University San Raffaele Scientific Institute Via Olgettina, 60 20132 Milan, Italy e-mail: pierro.luisa@hsr.it

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© 2016 American Academy of Optometry