Fig. 4
From: Keratectasia severity staging and progression assessment based on the biomechanical E-staging
“Biomechanical/tomographic assessment” Corvis ST® (Oculus, Wetzlar, Germany) examination of a right eye of a 39-year-old male keratoconus patient. Upper left: “Corvis ST – biomechanical assessment”: individual biomechanical parameters are displayed including stiffness parameter A1 (stiffness parameter on inward applanation), integrated radius, ARTh (Ambrósio relational thickness in horizontal), and DA ratio 2 mm (deformation amplitude ratio of 2 mm). Keratoconus population highlighted in red, normal population in green. Black vertical line marking the patient's value, indicating the group the patient belongs to. Lower left: deformation curve of the cornea after application of an air puff indentation. The Corvis Biomechanical Index (CBI) makes a quasi-binary decision between a healthy cornea (green, value zero) and keratoconus (red, value one) – in this example, the value is 0.99. Right: “Pentacam – tomographic assessment ” showing anterior radius of curvature, corneal thickness, pachymetric progression, maximum keratometry value (Kmax), inferior-superior value, Pentacam random forest index (PRFI), topographic keratoconus classification (TKC) and final Belin-Ambrósio enhanced ectasia display deviation index (BAD-D). The combination of the data from the Corvis ST® and the Pentacam® in the Tomographic Biomechanical Index (TBI) is also considered quasi-binary