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Talia R Kaden, Laurence T Sperber, George Asimellis, A. John Kanellopoulos; Corneal epithelial remodeling as a diagnostic tool for keratoconus: A comparison of 3-D Anterior Segment OCT in a large cohort of keratoconic and normal eyes. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):1632. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To use anterior-segment optical coherence tomography (AS-OCT) to investigate epithelial thickness distribution characteristics in keratoconic patients
The study group (A) consisted of 160 eyes with clinically diagnosed keratoconus and the control group (B) was composed of 160 non-keratoconic eyes. Employing anterior-segment OCT (RtVue-100, Optovue, Fremont, CA), three successive acquisitions were performed in each eye. 3-dimensional epithelial thickness maps were obtained, enabling investigation of epithelial thickness at the pupil center, mid-periphery, superior and inferior cornea. These data provided the average, maximum, minimum, and topographic epithelial thickness variability. Intra-individual variation of epithelial thickness measurement was also evaluated. We further investigated correlation of the epithelial data via newly defined Scheimpflug imaging-derived anterior-surface irregularity indices for keratoconus severity: the index of height decentration (IHD) and the index of surface variance (ISV). The epithelial thickness indices were then correlated with these two indices.
The average intra-individual epithelial thickness repeatability was 1.67μm in Group A (keratoconic group) and 1.13μm in Group B (control group). The pupil center epithelial thickness was 51.75±7.02 μm in the keratoconic group, and maximum and minimum thickness were 63.54±8.85 μm and 40.73±8.51 μm. In the control group, epithelial thickness at the center was 52.54±3.23 μm, maximum thickness was 55.33±3.27 μm and the minimum was 48.50±3.98 μm. Topographic variability was 6.07±3.55 μm in the keratoconic group, while 1.59±0.79 μm in the control group. Both epithelial thickness variability and range, defined as minimum-maximum, correlated tightly with the indices of IHD and ISV.
AS-OCT offers both ease of use and high predictability in assessing in-vivo epithelial thickness measurement in keratoconus. We have demonstrated that keratoconic eyes have an increased overall epithelial thickness as compared to normal eyes and that there exists a tight correlation between increased topographic thickness variability and range and keratoconus severity. Because epithelial thickness as measured by AS-OCT may be used to identify and assess mild and suspected cases of keratoconus, this technique is of particular clinical importance.
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