The biomechanical e‐staging—In vivo assessment of corneal biomechanics in keratoconus

Abstract

Aims/Purpose: Keratoconus (KC) is biomechanically characterized by a decreased resistance to deformation when compared to healthy corneas. The aim of this presentation is to give an overview about the development and clinical application of the recently introduced Homburg Biomechanical E‐Staging (BEST) for KC.Methods: The Corvis ST (Oculus, Germany) non‐contact pneumotonometer measures the corneal deformation after applying a standardized air puff. It calculates the quasi‐binary indices Corvis Biomechanical Index (CBI) and Tomographic Biomechanical Index (TBI) to separate healthy from ectatic corneas, without, however providing a biomechanical KC severity stage. The Homburg BEST based on the linearized CBI provides information about biomechanical KC severity in form of E‐stages 0 to 4, thus augmenting the existing tomographic ABCD KC classification by including corneal biomechanics. Several studies and results about the development and clinical application of the Homburg BEST are presented.Results: The Homburg BEST was developed based on two independent KC datasets (Homburg: n = 448, Milano/Rio: n = 860). Since 2022, it has been integrated into the Corvis ST software, thus providing a biomechanical KC severity and progression assessment. The software based on several individual biomechanical parameters indicates KC progression like tomographic progression parameters. However, it is influenced by corneal thickness measurements, increases within the first postoperative months after corneal crosslinking (CXL) and indicates postoperative KC stabilization more than 1 year after CXL. Intracorneal ring segment implantation permanently affects corneal thickness in the midperiphery and contributes to slightly higher postoperative BEST values.Conclusions: Although with limitations, the Homburg BEST enables a biomechanical staging and progression assessment in KC by considering several biomechanical parameters as an addition to the previously purely tomographic or even topographic analysis.