Repeatability assessment of anterior segment measurements in myopic patients using an anterior segment OCT with placido corneal topography and agreement with a swept-source OCT

Abstract

Background: The precision of anterior segment biometric measurements in eyes has become increasingly important in refractive surgery. The purpose of this study is to assess the repeatability of the automatic measurements provided by a new spectral-domain optical coherence tomograph (SD-OCT)/Placido topographer (MS-39, CSO) and its agreement with a swept-source OCT (SS-OCT) biometer (CASIA SS-1000, Tomey) in patients with myopia.

Methods: The right eye of 235 subjects was scanned 3 times with both devices. The evaluated parameters included central corneal radius of the steep meridian, central corneal radius of the flat meridian, mean central corneal radius, thinnest corneal thickness, central corneal thickness, anterior chamber depth, corneal volume and diameter. The intraobserver repeatability of the MS-39 measurements was calculated using intraclass correlation coefficient (ICC), within subject standard deviation, coefficient of repeatability, coefficient of variation and repeated-measures analysis of variance of the 3 repeated measurements. The agreement between the two devices was evaluated by 95% limits of agreement (LoA).

Results: The majority of the parameters acquired from MS-39 showed high repeatability. The repeatability of corneal diameter was slightly lower than the other measurements, although the ICC remained high. Agreement with the CASIA SS-1000 was good, indicated by the Bland-Altman plots with narrow 95% LoA values for all parameters assessed.

Conclusions: The high repeatability of automatic measurements by the new device supports its clinical application in eyes with myopia, and the good agreement between the two devices indicates they could be used interchangeably for the parameters evaluated.

Keywords: Agreement; Corneal thickness; Corneal volume; Keratometry; OCT; Repeatability.

Fig. 1

Bland-Altman plots comparing the anterior segment parameters between MS-39 and CASIA SS-1000 Bland-Altman plots comparing the values of (a) central corneal radius of the flat meridian (K_f), (b) central corneal radius of the steep meridian (K_s), (c) mean central corneal (K_m), (d) thinnest corneal thickness (TCT), and (e) central corneal thickness (CCT) obtained by the MS-39 (CSO) and CASIA SS-1000 (Tomey) (The solid line in the middle represents the mean difference, and the two dotted lines above and below represent the 95% limits of agreement (LoA)).