Corneal Strain Induced by Intracorneal Ring Segment Implantation Visualized With Optical Coherence Elastography

PURPOSE: To record the axial strain field in the cornea directly after creating a stromal tunnel and implanting an intracorneal ring segment (ICRS). METHODS: Freshly enucleated porcine eyes were obtained and assigned to either ICRS implantation, tunnel creation only, or virgin control groups. Immediately after manual tunnel creation and ICRS positioning, the entire eye globe was mounted on a customized holder and intraocular pressure (IOP) was adjusted to 15 mm Hg. Then, IOP was inreased to 20 mm Hg, in steps of 1 mm Hg. At each step, an optical coherence tomography volume scan was recorded. Displacements between subsequent scans were retrieved using a vector-based phase difference method. The induced corneal strain direction was determined by taking the axial gradient. In addition, corneal surface was detected and sagittal curvature maps computed. RESULTS: Corneal tissue presented a localized compressive strain in the direct vicinity of the stromal tunnel, which was independent of IOP change. The central and peripheral (exterior to the ICRS) cornea demonstrated compressive strains on IOP increase, and tensile strains on IOP decrease. ICRS implantation induced an annular-shaped tensile strain at its inner border, particularly during IOP increase. The compressive strains close to the tunnel remained after ICRS implantation. Corneal curvature changes were concentrated on regions where strain was induced. CONCLUSIONS: ICRS implantation induces localized strains in the regions subjected to refractive changes, suggesting that corneal strain and curvature are directly related. Studying corneal strain in response to surgical intervention may provide new insights on underlying working principles.

Automated summary

This study directly records the strain field in the cornea after stromal tunnel creation and implantation of an intracorneal ring segment. The results show that implantation of the ring segment induces localized strains in the regions subjected to refractive changes, which suggests a direct relationship between corneal strain and curvature. Understanding corneal strain in response to surgical intervention may provide new insights on underlying working principles.