Comparison of Scheimpflug Imaging (Pentacam HR) and Swept-Source Optical Coherence Tomography (CASIA2) in Eyes With Macular Corneal Dystrophy

Abstract

Purpose: Assessment of tomographic characteristics and interdevice comparability between Scheimpflug imaging (Pentacam HR, Oculus Optikgeräte GmbH, Wetzlar, Germany) and swept-source optical coherence tomography (CASIA2, Tomey Corp., Nagoya, Japan) in eyes with macular corneal dystrophy (MCD). Methods: Eyes with MCD were examined by Pentacam HR and CASIA2. Interdevice comparison was performed using a Wilcoxon matched pairs test and Bland–Altman plots with 95% limit of agreement. A Spearman rank correlation coefficient was used for correlating indices of both devices. Results: This retrospective study included 31 eyes of 18 patients (mean age: 32.1 ± 10.7 years). Eyes with MCD demonstrated a moderate astigmatism with a Cylinder anterior of 2.56 ± 1.50 D (Pentacam HR) and 2.52 ± 1.57 D (CASIA2) without a difference between both devices. CASIA2 (0.34 ± 0.14 D) measured lower values of Cylinder posterior compared with Pentacam HR (0.96 ± 0.66 D) (P < 0.0001). Comparison of pachymetry (Pentacam HR vs. CASIA2) showed higher values of the central corneal thickness (619 ± 227 μm vs. 445 ± 67 μm, P = 0.0001) and the thinnest corneal thickness (499 ± 165 μm vs. 430 ± 60 μm, P = 0.0167) for Pentacam HR. Corneal densitometry measurement revealed that increasing gray scale units caused a greater interdevice difference for pachymetry values, as Pentacam HR measured higher than CASIA2 for more opaque corneas. Conclusions: Eyes with MCD tend to have thinner corneas and a higher amount of corneal astigmatism than healthy eyes. In advanced MCD, Scheimpflug technology may mistakenly overestimate corneal thickness. The pachymetry measurement of the optical coherence tomography should be used when planning corneal surgery such as excimer laser-assisted phototherapeutic keratectomy to determine the ablation depth.