Comparison of Central Corneal Thickness Measurements with Ultrasound Pachymetry, Anterior Segment Optical Coherence Tomography and Specular Microscopy
Comparison of Central Corneal Thickness Measurements with Ultrasound Pachymetry, Anterior Segment Optical Coherence Tomography and Specular Microscopy
Author(s):Dr Ashan H
Received: 2020-05-11
Accepted: 2020-06-09
Published: 2020-06-26
Abstract
Purpose: To measure and compare central corneal thickness (CCT) obtained with ultrasound pachymetry (USP), anterior segment optical coherence tomography (AS-OCT), and non-contact specular microscopy (SM), and to assess the agreement and interchangeability of the three techniques in healthy eyes.
Methods: In this prospective, comparative, cross-sectional study, CCT was measured in healthy eyes without ocular disease other than refractive error. For each eye, CCT was obtained in the same session by AS-OCT and SM (both non-contact) followed by USP (contact), performed by the same examiner. Mean CCT values were compared using repeated-measures analysis of variance, correlations were assessed with the Pearson coefficient, and agreement was evaluated using Bland–Altman analysis with 95% limits of agreement.
Results: All three devices produced closely comparable mean CCT values, and correlations between methods were strong. USP tended to yield the thickest readings and AS-OCT the thinnest, with specular microscopy intermediate to slightly higher. Although mean differences between devices were small, the 95% limits of agreement were wide enough to be clinically relevant, indicating that the instruments are not directly interchangeable.
Conclusion: USP, AS-OCT, and SM show strong correlation and overall good agreement in measuring CCT in healthy eyes. However, systematic differences and clinically meaningful limits of agreement mean that the values are not interchangeable; the same device should be used for serial monitoring of an individual patient.
Methods: In this prospective, comparative, cross-sectional study, CCT was measured in healthy eyes without ocular disease other than refractive error. For each eye, CCT was obtained in the same session by AS-OCT and SM (both non-contact) followed by USP (contact), performed by the same examiner. Mean CCT values were compared using repeated-measures analysis of variance, correlations were assessed with the Pearson coefficient, and agreement was evaluated using Bland–Altman analysis with 95% limits of agreement.
Results: All three devices produced closely comparable mean CCT values, and correlations between methods were strong. USP tended to yield the thickest readings and AS-OCT the thinnest, with specular microscopy intermediate to slightly higher. Although mean differences between devices were small, the 95% limits of agreement were wide enough to be clinically relevant, indicating that the instruments are not directly interchangeable.
Conclusion: USP, AS-OCT, and SM show strong correlation and overall good agreement in measuring CCT in healthy eyes. However, systematic differences and clinically meaningful limits of agreement mean that the values are not interchangeable; the same device should be used for serial monitoring of an individual patient.
Keywords: central corneal thickness; ultrasound pachymetry; anterior segment optical coherence tomography; specular microscopy; agreement; Bland–Altman
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