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H. Li, C. K. S. Leung, C. Y. L. Cheung, A. L. Wong, R. Weinreb, D. S. C. Lam, C. P. Pang; Agreement of Central Corneal Thickness Measurement Between Visante OCT and SLOCT. Invest. Ophthalmol. Vis. Sci. 2007;48(13):3873.
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Visante OCT and SLOCT are the two commercially available optical coherence tomographers designed for imaging the anterior segment. Both instruments can provide non-contact measurement of corneal thickness. In this study, we compared central corneal thickness (CCT) measured by Visante OCT, SLOCT and ultrasound pachymetry and evaluated their agreements.
Forty normal subjects were invited for CCT measurement on one randomly selected eye using Visante OCT (Carl Zeiss Meditec, Dublin, CA), SLOCT (Heidelberg Engineering, GmbH, Dossenheim, Germany) and ultrasound pachymetry ((Micropach Model 200P, Sonomed Inc, USA). For Visante OCT and SLOCT measurements, a horizontal scan (16mm in Visante OCT; 15mm in SLOCT) bisecting the pupil was captured and the CCT was automatically determined by the built-in analysis software. Each eye was imaged 3 times and the average CCT was calculated. CCT measurements were compared with ANOVA with Turkey post hoc test. Bland and Altman plots were used to evaluate agreement between instruments.
CCT (+/-SD) measured by Visante OCT, SLOCT and ultrasound pachymetry were 538.0+/-31.6µm, 568.4+/-32.0µm and 555.3+/-32.3µm, respectively. Visante OCT CCT measurement was lower than that obtained by SLOCT (p=0.044) and ultrasound pachymetry (p<0.001). No significant difference was found between SLOCT and ultrasound pachymetry CCT (p=0.164). The mean difference / 95% limits of agreement were 30.4µm / 40.0µm between Visante OCT and SLOCT; 17.3µm / 43.1µm between Visante OCT and ultrasound pachymetry; and 13.1µm / 48.3µm between SLOCT and ultrasound pachymetry.
Poor agreement for CCT measurement was found between Visante OCT and SLOCT despite the fact that the imaging principle of both instruments is the same. Compared to ultrasound pachymetry, Visante OCT underestimated CCT.
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