Repeatability and Reproducibility of the ArcScan Insight 100 VHF Digital Ultrasound

INCLUSION CRITERIA Only patients who are medically suitable for corneal refractive surgery can be included in the study. As general inclusion criteria the following aspects are defined: * Subjects should be 21 years of age or older. * Contact lens wearers must stop wearing their contact lenses at least four weeks per decade of wear before baseline measurements in case of hard contact lenses and one week before baseline measurements in case of soft contact lenses. * Patient will be able to understand the patient information and willing to sign an informed consent. For the repeatability and reproducibility phase using normal eyes of the study: * Eyes with no ocular pathology * Eyes with no previous ocular or corneal surgery For the repeatability and reproducibility phase using post-LASIK eyes of the study: • Eyes between 3 and 9 months after LASIK or SMILE For the comparison of ArcScan Insight 100 VHF digital ultrasound with RTVue OCT • Either eyes before or after corneal refractive surgery EXCLUSION CRITERIA * Previous ocular or corneal surgery (for normal eyes) * Patient not being able to tolerate local or topical anesthesia * Patient has active conjunctivitis or any active ocular infection or inflammation * Patient has a corneal ulcer * Patient has an open wound on the corneal epithelium * Patient has compromised epithelium (e.g. ≥Grade 3 superficial punctate keratitis) * Pregnancy