Agreement in anterior segment measurements between swept-source optical coherence and dual Scheimpflug tomography devices in keratoconus eyes

Abstract

Purpose: To evaluate the agreement of ocular biometry measured using a swept-source optical coherence (Casia 2) and a dual Scheimpflug (Galilei G6) tomography in keratoconus.

Methods: This retrospective study included 102 eyes from 102 keratoconus patient examined using both devices. Parameters compared included flat (Kf) and steep (Ks) keratometry, astigmatism of anterior, posterior, and total keratometry, central (CCT) and thinnest (TCT) corneal thickness. To assess the agreement, intraclass coefficient (ICC) and Bland-Altman analysis with 95% limits of agreement (LoA) were used.

Results: Anterior and total Ks and Kf showed moderate or good agreement with 95% limits of agreement (LoA) range over 9.75 D. Posterior Ks and Kf were lower in the Galilei G6 (all p < 0.001). Astigmatism showed moderate, poor, and moderate agreement for anterior, posterior, and total keratometry, respectively. CCT and TCT showed excellent agreement; however, the 95% LoA range was over 60 μm.

Conclusion: The agreement between the two devices was not excellent for most parameters used to diagnose keratoconus and assess disease progression, and the differences were clinically significant. Therefore, the measurements from these two devices are not interchangeable for patients with keratoconus.

Keywords: Casia 2; Dual Scheimpflug tomography; Galilei G6; Keratoconus; Swept-source optical coherence tomography.

Fig. 1

The Bland-Altman plots of the (a) anterior Ks, (b) anterior Kf, (c) ACA, (d) posterior Ks, (e) posterior Kf, (f) PCA, (g) total Ks, (h), total Kf, (i) TCA, (j) CCT, (k) TCT, and (l) ACD. The solid line represents the mean difference, while the dotted lines on each side show upper and lower 95% LoA. K = keratometry; s = steep; f = flat; ACA = anterior corneal astigmatism; PCA = posterior corneal astigmatism; TCA = total corneal astigmatism; CCT = central corneal thickness; TCT = thinnest corneal thickness; ACD = anterior chamber depth; D = diopters; LoA = limits of agreement.