The CBI was developed in order to detect early biomechanical changes in case of an early ectasia. It is based on a logistic regression formula including different Dynamic Corneal Response (DCR) parameters, the Stiffness Parameter and the corneal thickness profile of the horizontal sectional plane. In a large multicentre study the high accuracy of this index to distinguish normal eyes from eyes with keratoconus was proven. In this study including more than 600 eyes the accuracy was higher than 98 percent. Moreover, the clinical use of this index in case of subclinical or forme fruste keratoconus was proven in another publication. Many of these cases could be detected by the CBI, even though no topographic or tomographic abnormalities could be observed. These case examples support the hypothesis that biomechanical changes occur before morphological changes are present.