Epithelial Thickness Mapping in Keratoconic Corneas: Repeatability and Agreement Between CSO MS-39, Heidelberg Anterion, and Optovue Avanti OCT Devices

PURPOSE:To assess repeatability and agreement of corneal epithelial thickness mapping in eyes with keratoconus using three optical coherence tomography (OCT) devices featuring different technologies: spectral-domain (SD) OCT combined with Placido disk corneal topography (MS-39), swept-source OCT (Anterion), and SD-OCT (Avanti). METHODS:Three consecutive measurements were acquired with the three devices in 60 eyes with keratoconus. The mean epithelial thickness was calculated in the central 2-mm zone and in 2- to 5-mm and 5- to 7-mm diameter rings. The repeatability was calculated using pooled within-subject standard deviation (Sw). The agreement was assessed by paired t tests and Bland-Altman plots. RESULTS:The repeatability (Sw) of the epithelial thickness for the central 2-mm zone was 0.91, 0.71, and 0.93 μm for the MS-39, Anterion, and Avanti, respectively. All thicknesses with the MS-39 were greater than those of the Anterion and Avanti, with mean differences of 4.11 ± 1.34 μm (P < .001) and 0.52 ± 1.30 μm (P = .003), respectively. The 95% limits of agreement were 1.484 to 6.736 μm for the MS-39 and Anterion, −3.068 to 2.028 μm for the Avanti and MS-39, and 1.258 to 5.922 μm for for the Avanti and Anterion. CONCLUSIONS:Epithelial thickness mapping results were most repeatable with the Anterion, followed by the MS-39 and Avanti. The MS-39 gave the thickest values, followed by the Avanti and Anterion. The differences were significant, making the devices not interchangeable for epithelial thickness mapping in eyes with keratoconus

Heidelberg Anterion Swept-Source OCT Corneal Epithelial Thickness Mapping: Repeatability and Agreement With Optovue Avanti

PURPOSE: To assess the repeatability of corneal epithelial thickness mapping in virgin, post-laser refractive surgery (PLRS), and keratoconic eyes using a novel swept-source optical coherence tomographer (SS-OCT), and to determine the agreement of the measurements with a validated spectral-domain (SD) OCT. METHODS: Analysis of 90 virgin, 46 PLRS, and 122 keratoconic eyes was performed. Three consecutive measurements of each eye were acquired with the Anterion SS-OCT and Avanti SD-OCT devices, and averages of the epithelial thickness mapping were calculated in the central 2-mm zone and in the 2- to 5-mm and 5- to 7-mm diameter rings. The repeatability was analyzed using pooled within-subject standard deviation (Sw). The agreement was assessed by Bland-Altman analysis and paired t tests. RESULTS: The repeatability ranges of the Anterion and Avanti epithelial thickness mapping measurements were Sw: 0.60 to 1.36 µm and Sw: 0.75 to 1.96 µm, respectively. The 95% limits of agreement of the Anterion and Avanti were 0.826 to 8.297. All values of the thickness measurements with the Anterion were lower than those of the Avanti, with the mean differences being 4.06 ± 1.81, 3.26 ± 2.52, and 3.68 ± 2.51 µm in virgin, PLRS, and keratoconic eyes, respectively (P < .001 for all). CONCLUSIONS: The repeatability of the Anterion's epithelial thickness mapping was higher than that of the Avanti. In terms of the agreement between the Anterion and Avanti, the epithelium measured by the Anterion was always thinner than that of the Avanti, making their interchangeable use unsuitable without corrections

Epithelial, Stromal, and Total Corneal Thickness in Keratoconus: Three-dimensional Display With Artemis Very-high Frequency Digital Ultrasound

Purpose: To characterize the epithelial, stromal, and total corneal thickness profile in a population of eyes with keratoconus. Methods: Epithelial, stromal, and total corneal thickness profiles were measured in vivo by Artemis very high-frequency (VHF) digital ultrasound scanning (ArcScan) across the central 6- to 10-mm diameter of the cornea on 54 keratoconic eyes. Maps of the average, standard deviation, minimum, maximum, and range of epithelial, stromal, and total corneal thickness were plotted. The average location of the thinnest epithelium, stroma, and total cornea were found. The crosssectional semi-meridional stromal and total corneal thickness profiles were calculated using annular averaging. The absolute stromal and total corneal thickness progressions relative to the thinnest point were calculated using annular averaging as well as for 8 semi-meridians individually. Results: The mean corneal vertex epithelial, stromal, and total corneal thicknesses were 45.7± 5.9 μm, 426.4 ± 38.5 μm and 472.2 ± 41.4 μm respectively. The average epithelial thickness profile showed an epithelial doughnut pattern characterized by localized central thinning surrounded by an annulus of thick epithelium. The thinnest epithelium, stroma, and total cornea were displaced on average by 0.48 ± 0.66 mm temporally and 0.32 ± 0.67 mm inferiorly, 0.31 ± 0.45 mm temporally and 0.54 ± 0.37 mm inferiorly, and 0.31 ± 0.43 mm temporally and 0.50 ±0.35 mm inferiorly, respectively, with reference to the corneal vertex. The increase in semimeridional absolute stromal and total corneal thickness progressions was greatest inferiorly and lowest temporally. Conclusions: Three-dimensional thickness mapping of the epithelial, stromal, and total corneal thickness profiles characterized thickness changes associated with keratoconus and may help in early diagnosis of keratoconus