Can the Corvis ST Estimate Corneal Viscoelasticity?
Author: Abass, A., Roberts, C.J., Lopes, B., Eliasy, A., Vinciguerra, R., Ambrósio, R., Vinciguerra, P., and Elsheikh, A.
Journal: Journal of Refractive Surgery
Publication Date: Feb 2020
Summary:
In our research, we examined the potential of the Corvis ST device to estimate corneal viscoelasticity. This is important because understanding the biomechanical properties of the cornea can help detect and manage corneal conditions, such as keratoconus.
The study we focused on used mathematical models to analyze data from the Corvis ST device. While we agree with many of the study's findings, we would like to discuss some limitations of the analysis and provide our views on how to estimate corneal viscoelasticity better.
First, we noticed that the study's mathematical analysis lacked validation and could have been improved by comparing closed-form analysis with inverse finite element analysis. This comparison is essential to ensure accurate results and a reliable understanding of corneal biomechanics.
Second, we found some omissions in the study that could have affected the results. For example, the researchers did not consider the inertia or mass force in their analysis, which is important in dynamic systems like air-puff excitation. Additionally, they used an incorrect calculation for the cross-sectional area of the air-puff, resulting in an overestimation of force.
Our research suggests that the best way to estimate corneal viscoelasticity is to focus on hysteresis, which can be determined from the pressure-deflection behavior recorded by devices like the Corvis ST and the Ocular Response Analyzer (ORA). Using parameters like corneal hysteresis and hysteresis loop area can help differentiate between healthy and keratoconic corneas.
Lastly, we would like to point out that the study's methodology could be improved by clarifying the inclusion criteria for fellow eyes of patients with asymmetric keratoconus. This is important because keratoconus is a bilateral but asymmetric disease, and the study's classification of these cases could have affected the results.
In conclusion, our research emphasizes the importance of validation and a comprehensive approach to understanding corneal biomechanics. By refining the methods used to estimate corneal viscoelasticity, we can improve our ability to detect and manage corneal conditions, ultimately benefiting patients and healthcare providers.