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Luisa Pierro, Marco Gagliardi, Giuseppe Parrinello, Paolo Rama, Francesco Bandello; Healthy Eyes Central Corneal Thickness Reproducibility Using 8 Optical Instruments and 1 Ultrasonic Instrument. Invest. Ophthalmol. Vis. Sci. 2012;53(14):132.
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© ARVO (1962-2015); The Authors (2016-present)
Central corneal thickness (CCT) measurements (pachymetry) have become integral for the diagnosis and management of various ocular conditions. CCT measurements can be performed using ultrasonic-based or optic-based techniques. The gold standard has been ultrasonic pachymetry. Aim of this study was to assess CCT inter- and intra-operator reproducibility using 8 optical instruments (6 Spectral Domain OCT, 1 Time Domain OCT and 1 Scheimpflug Camera) and 1 ultrasonic instrument.
CCT was measured in the right eye of 34 randomly chosen healthy subject (18 women, 16 men, mean age 44±10,6 years) by 2 masked operators using 1 ultrasound device (Pachmate DGH55, DGH Instruments, Inc.), 6 SD-OCT (Spectral OCT/SLO, Opko; Cirrus HD-OCT, Zeiss; 3D OCT-2000, Topcon; RS-3000, Nidek; RtvUe-100, Optovue; SS-1000 CASIA, Tomey), 1 TD-OCT (Visante, Zeiss) and 1 Scheimpflug Camera (Sirius, C.T.O.). Exclusion criteria were: history of corneal and anterior segment surgery, corneal diseases, use of contact lens. Both operators repeated two consecutive measurements of each subject during the same day. Inter- and intra-operator reproducibility was evaluated by Intraclass Correlation Coefficient (ICC), Coefficient of Variation (CV) and Bland-Altman plot. Instruments-to-instruments reproducibility was determined by ANOVA for repeated measures; post hoc test for differences among instruments was also evaluated.
Mean CCT ranged from 536.38µm (SD 42.13) to 576.92µm (SD 39.72). Visante and Sirius showed the lowest value in all measurements, 3DOCT 2000 and Spectral OCT/SLO showed the highest. While ICC and CV showed excellent inter- and intra-operator reproducibility for all optic-based devices (best results obtained by CASIA with CV<0,06% and ICC=1 for both inter- and intra-operator reproducibility), inter- and intra-operator reproducibility for Pachmate DGH55 was just good (CV<1.01% and ICC>0,87 for both inter- and intra-operator reproducibility). Bland-Altman plots confirmed these results.
Optic-based instruments showed best intra- and inter-operator reproducibility than ultrasound pachymetry. All optic-based instruments, except Spectral OCT/SLO and 3D OCT-2000, measured thinner CCT than ultrasonic-based instrument. In clinical practice CCT measurements acquired by optical and ultrasound modalities are not directly interchangeable.
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