Very high-frequency (VHF) digital ultrasound was first used in 1993 to obtain images and measure the thickness of the cornea (the window at the front of the eye) and the layers within the cornea, such as the epithelium (the layer of skin on the surface of the cornea). A commercially available instrument, known as the Artemis, has been used in routine clinical practice since 2001. The ArcScan Insight 100 VHF digital ultrasound scanner is an updated version, which obtained CE mark in 2016.~Optical coherence tomography (OCT) is another method of measuring the thickness of the cornea and the corneal epithelium. OCT has been used for measuring corneal thickness since 1997 and the technology had evolved to also measure epithelial thickness since 2012. There are currently three OCT scanners capable of measuring epithelial thickness; Carl Zeiss Meditec Cirrus HD OCT 5000, Optovue RTVue OCT, CSO MS-39 OCT.~The aim of the study is to establish the repeatability (i.e. the variability in measurements taken by a single examiner during a single visit) and reproducibility (i.e. the variability in measurements taken in the same conditions between two examiners) for each of the four devices for measuring corneal thickness and epithelial thickness.
The purpose of this study is to evaluate the repeatability and reproducibility of corneal, epithelial, and LASIK flap thickness using the Carl Zeiss Meditec Cirrus HD OCT 5000, Optovue RTVue OCT, CSO MS-39 OCT, and ArcScan Insight 100 very high-frequency digital ultrasound arc-scanner.