Comparison of corneal thickness in patients with dry eye disease using the Pentacam rotating Scheimpflug camera and anterior segment optical coherence tomography

Abstract

The purpose of this study was to compare central corneal thickness, thinnest corneal thickness, and the thinnest point of the cornea between Pentacam and anterior segment optical coherence tomography (ASOCT) in patients with dry eye disease (DED). This cross-sectional study included 195 participants between November 2015-June 2017. DED was diagnosed using the Asia Dry Eye Society criteria and further divided into mild and severe DED based on kerato-conjunctival vital staining. Central corneal thickness, thinnest corneal thickness, and the thinnest point of the cornea measured by Pentacam and ASOCT were compared, and Pearson's correlation coefficients were estimated. The differences in central corneal thickness and the thinnest corneal thickness between Pentacam and ASOCT were analysed using Bland-Altman and multivariate regression analyses adjusted for age and sex. This study included 70 non-DED subjects and 52 patients with mild and 73 with severe DED. The Pentacam and ASOCT measurements of central corneal thickness and thinnest corneal thickness were strongly correlated, but the respective values were higher when measured with Pentacam. The Bland-Altman analysis revealed differences in central corneal thickness (non DED, 11.8; mild DED, 13.2; severe DED, 19.6) and in thinnest corneal thickness (non DED, 13.1; mild DED, 13.4; severe DED, 20.7). After adjusting for age and sex, the differences in central corneal thickness (β = 7.029 μm, 95%CI 2.528-11.530) and thinnest corneal thickness (β = 6.958 μm, 95%CI 0.037-13.879) were significantly increased in the severe-DED group. The distribution of the thinnest point of the cornea in the cornea's inferior temporal quadrant between Pentacam and ASOCT deviated in severe DED (Pentacam: 90.4% vs. ASOCT: 83.6%). Clinicians should consider that there were significant differences in corneal-morphology assessment between the measurements with Pentacam and ASOCT in severe DED.

Fig 1. Comparison of corneal thickness assessment between Pentacam and ASOCT in patients with Dry Eye Disease.

(A) The central corneal thickness and (B) the thinnest points of the cornea were compared between Pentacam and ASOCT according to the subgroups. Data are considered statistically significant at ***P < 0.001. DED: dry eye disease, ASOCT: anterior segment optical coherence tomography.

Fig 2. Bland–Altman plot for central corneal thickness and thinnest point of the cornea for Pentacam and ASOCT.

The x-axis indicates the average of the thickness between the Pentacam and ASOCT measurements, and the y-axis indicates the difference between Pentacam and ASOCT (Pentacam-ASOCT). The central line indicates the mean difference (bias) between the normalized thickness from the two devices, whereas the superior and inferior lines depict the intervals that include 95.6% of all differences. (A)–(C) show the bias for CCT and (D)–(E) for TCT. ASOCT: anterior segment optical coherence tomography, CCT: central corneal thickness, TCT: thinnest corneal thickness.

Fig 3. Location of the thinnest point of the cornea as measured by Pentacam and ASOCT.

The location of the thinnest point of the cornea was mapped from its quadrant location using Pentacam and ASOCT based on the (A) non-DED group, (B) mild-DED group, and (C) severe-DED group. DED: dry eye disease, ASOCT: anterior segment optical coherence tomography.