Agreement and repeatability of central corneal thickness measurements made by ultrasound pachymetry and anterior segment optical coherence tomography

Abstract

PurposeTo evaluate repeatability within and between examiners and to assess agreement in corneal thickness measurements obtained by anterior segment optical coherence tomography (ASOCT) and ultrasonic pachymetry (USP). MethodsThis was a prospective, observational study. Fifty-one patients who visited a glaucoma service with suspected glaucoma, glaucoma, or cataract were enrolled. Patients with a history of corneal surgery or abnormalities and those who were uncooperative for examinations were excluded. Each patient underwent ASOCT followed by USP, with each test performed by two different examiners. Measurement repeatability was evaluated using intraclass correlation coefficient (ICC) values. Agreement in corneal thickness measurements was evaluated by the Bland and Altman plot method. Linear regression analysis was used to assess the relationship between ASOCT and USP measurements. ResultsUSP and ASOCT corneal thickness measurements revealed high intraexaminer and interexaminer repeatability (ICCs ≥ 0.978). ASOCT corneal thickness measurements of a central 2-mm zone showed higher intraexaminer (ICC = 0.999) and interexaminer (ICC = 0.999) repeatability than USP measurements or ASOCT measurements of the vertex. The 95% limit of agreement (LoA) between the vertex-centered ASOCT and the USP scan was between 3.68 and 24.76 μm. The 95% LoA between the central 2-mm zone ASOCT and the USP scan was between 3.75 and 23.39 μm. Average ASOCT corneal thickness was less than USP measurements, but ASOCT thickness could be converted to USP thickness through linear regression equations. ConclusionBoth devices have good intraexaminer and interexaminer repeatability, though ASOCT has slightly better interexaminer repeatability. ASOCT accurately and reliably measures corneal thickness in a noninvasive manner.