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A. N. Kuo, M. Zhao, S. Farsiu, J. A. Izatt; SDOCT Measurement of Corneal Power and Comparision With Standard Techniques. Invest. Ophthalmol. Vis. Sci. 2010;51(13):5814.
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© ARVO (1962-2015); The Authors (2016-present)
Volumetric spectral domain optical coherence tomography (SDOCT) images of the cornea can be used to extract clinically important information such as power without the limitations inherent to traditional corneal imaging modalities. Here, we present a comparison of central corneal power as measured by SDOCT, topography, and Scheimpflug photography.
Fifteen left eyes of fifteen healthy volunteers were imaged in this IRB approved study. Each cornea was imaged by SDOCT (Bioptigen with corneal adapter), topography (Atlas; Carl Zeiss Meditec), and Scheimpflug photography (Pentacam; Oculus). The SDOCT volumes comprised 50 radial B-scans each and were processed offline to correct for acquisition artifacts including gross patient motion during the 2.5s acquisition and to segment the surfaces in a semi-automated fashion.For this study, corneal power for topography was defined as the power value at 0mm, for Scheimpflug photography was the mean equivalent K reading for the central 3mm diameter zone, and for SDOCT was the central refractive power as determined using custom software that spherically fit the corrected anterior and posterior corneal surfaces within the central 3mm diameter zone with conversion to refractive power using the thin lens approximation.Bland-Altman plots were generated to qualitatively compare the corneal powers as measured by the different instruments. Paired, two-tailed t-tests were used to examine the significance of the differences in measured corneal power between SDOCT and the other two instruments. Intraclass correlations were also calculated.
The mean difference in central corneal power as measured by SDOCT and topography was -0.014 D (SD ±1.25 D, p=0.966). The intraclass correlation between SDOCT and topography was 0.78. The mean difference as measured by SDOCT and Scheimpflug photography was 0.28 D (SD ±1.09 D, p=0.3395). The intraclass correlation between SDOCT and Scheimpflug photography was 0.73. There was no trending of the differences with increasing or decreasing powers with either comparison.
Differences in central corneal power in this study population as measured by SDOCT when compared to topography or Scheimpflug photography were not found to be statistically significant. The standard deviations and intraclass correlations, however, reflect variability in individual measurements and are likely due to uncorrected motion error from the temporal nature of SDOCT acquisition.
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