Effects of intracorneal ring segments on the biomechanical response of the ectatic cornea to air-puff: A patient-specific numerical analysis

Abstract

The assessment of the underlying factors that influence the biomechanics and dynamics of the cornea is essential for preserving the safety and efficacy of refractive surgeries. In the present work, the operated cornea with intracorneal ring segments (ICRSs) in a patient-specific finite-element model (FEM) was subjected to the air-puff. Then, the dynamic deformation parameters predicted by the FEM were obtained and compared with the corresponding values in clinical measurements. In this study, the effects of ICRS design, position, and implementation procedure in six different surgical scenarios were examined on the induced corneal stresses, deformation behavior, and shape regularization. While surgical scenarios with arc lengths of 160° (single and double segment), 355° implemented with the tunnel incision method provided similar maximum apical displacement (MAD) and highest concavity radius of curvature HCR), they induced significantly different flattening effects. The surgical scenarios with the segment of 160° arc-length implemented in nasal–temporal direction showed an approximately 15% higher reduction in mean corneal power ([Formula: see text]) value than the superior–inferior direction. From a solid-mechanics perspective, the study of ICRS mechanics in the cornea also confirmed the importance of the implementation position to achieve satisfactory flattening outcomes. Comparison of the two types of ICRS implementation procedures showed that, although the pocket method demonstrated a 10.23% higher MAD, it induced a higher reduction in the HCR of 21.65% compared with tunnel incision. The developed numerical model demonstrated the direct correlation of the ICRS insertion site with induced contact stresses and ICRS position stability. The study hypothesizes the significant influence of ICRS implementation position and procedure on the corneal biomechanical and dynamical behaviors. The proposed approach can be assessed as a robust and novel framework for planning optimized corneal refractive surgeries.

Evaluation of dynamic corneal response parameters and the biomechanical E-staging after Intacs® SK implantation in keratoconus

“…[ 3 8 9 10 ] Regarding tomography, there is consensus in the existing literature that ICRS implantation causes flattening of the cornea, thereby reducing myopic refraction and finally improving the uncorrected and corrected distance visual acuity of KC patients. [ 3 11 12 13 ] The mechanism of action of ICRS has been described via an arc-shortening effect within the cornea due to the added implant volume in the cornea. [ 14 ] An additional “artificial-limbus effect” caused by continuous ICRS has also been reported.…”