Corneal Buckling during Applanation and Its Effect on the Air Pressure Curve in Ocular Response Analyzer

The paper presents, for the first time, corneal buckling, during the air puff applanation, recorded with use of Ocular Response Analyzer (ORA), when the cornea is deeper deformed after its applanation. Precise numerical analysis of the air pressure curve from the raw data, distinct local disturbances of the curve, which appear almost exactly at the time of the first and the second applanations. Thirty measurements taken on six eyes show clear dependencies between times of both applanations and appearances of local wave disturbances on the air pressure curve as well as between the amplitude of pressure wave disturbances and the respective height of applanation curve. These findings can be interpreted as a result of very fast corneal buckling, that produces the air pressure wave, propagating from the cornea towards the device. The quantitative dependencies measured and described in this study, enable to characterize the individual buckling during respective applanations. Due to these individual characterizations and dependencies it is possible to understand and describe better the ultrafast corneal applanation process. Such phenomena could likely be employed to increase the accuracy of measured parameters by ORA or for identifying new types of biomechanical properties of the cornea.