Comparison of Two Optical Coherence Tomography Devices in Corneal Epithelial Thickness Maps

In total 50 eyes of 50 patients will be included, divided into two groups: study group comprised of 20 eyes with diagnosed keratoconus and a control group formed out of 30 healthy eyes. Patients included in the study will be measured with the corneal acquisition mode, also allowing for epithelium thickness data, on each device without pupil dilatation. After each measurement patients will be asked to blink in order to allow adequate tear-film recovery. Each patient will be measured three times with both devices. Only one visit will be necessary. The order in which the measurements will be performed (Anterion or MS-39) will be randomised using randomised.org. The corneal epithelial thickness will be measured as the distance between the air-tear and the epithelium-Bowman interfaces. Main outcome variable: \- Mean differences in central corneal epithelial thickness between the devices investigated (+ limits of agreement (1.96xSD) between the investigated devices) Secondary outcome variables: * Repeatability coefficient (within subject standard deviation - SD) and coefficient of variation of the two devices * Comparison in epithelial thickness between normal and keratoconus eyes * Sensitivity and specificity of swept-source OCT device in keratoconus diagnosis