Abstract
Purpose :
To evaluate the regional corneal biomechanical deterioration associated with keratoconus (KC) progression as measured by the Stress-Strain Index (SSI) maps.
Methods :
The preoperative examinations of 42 progressive KC cases that underwent corneal cross-linking (CXL) treatment were evaluated. The examinations included the tomography and the SSI measured by the Pentacam HR and the Corvis ST (Oculus, Wetzlar, Germany), respectively. The results were recorded at two different time points, the latter of which was at the last clinic visit before the CXL procedure. The patient-specific SSI maps were produced using data at each examination, based on finite element modelling and employing inverse analysis to represent the regional variation of biomechanical stiffness across the corneal surface.
Results :
All the 42 cases considered presented significant shape progression (above the 95% CI of repeatability) in anterior and posterior radii of curvature and minimum thickness. The overall corneal stiffness as measured by the SSI within the central 8 mm-diameter area underwent slight but significant reductions from the first to the last examination (−0.03 ± 0.02, range: −0.12 to 0, p < 0.001), Figure 1. In all 42 cases, the reduction in stiffness was localised and concentred in the area inside the keratoconus cone. The SSI values inside the cone were significantly lower in the last examination (by 0.16 ± 0.11, range: −0.53 to −0.01, p < 0.001), while the SSI outside the cone presented minimal, non-significant variations (0 ± 0.01, range: −0.05 to 0.03, p = 0.995).
Conclusions :
It has been observed through the SSI maps that the regional deterioration in stiffness was concentrated inside the area of pathology, while only mild non-significant alterations took place outside that area.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.