Abstract
Purpose :
To investigate the depth-dependent biomechanical effect of corneal cross-linking (CXL) in the human corneal stroma, and correlate it with stromal microstructural changes examined by transmission electron microscopy (TEM).
Methods :
Fresh human corneal lenticules (n = 124) were cut into two strips, and one was used as a treatment strip. This strip was superimposed until its thickness reached about 500 μm and divided into three groups, each randomly receiving a different CXL protocol: standard, accelerated, or control. Elasticity and viscidity were quantified using stress-strain extensometer. TEM was used to visualize the collagen fiber diameter and the interfibrillar spacing.
Results :
The relative change in Young’s modulus (rel. ΔE) decreased nonlinearly with increasing stromal depth both in the standard and accelerated groups. Compared to the sham controls, the rel. ΔE of standard and accelerated groups significantly increased in the anterior 400 μm and 275 μm depth, respectively. Also, the relative change in stress (rel. ΔS) was significantly lower after standard and accelerated CXL than controls. Depth analysis showed similar results for the elastic effect. TEM images showed a small, non-significant increase in fibril diameter. The interfibrillar spacing decreased significantly after standard and accelerated CXL in the anterior-mid region.
Conclusions :
CXL treatment produces a stiffer cornea with lower viscosity. The increase in corneal stiffness is related to a decrease in interfibrillar spacing. The accelerated procedure is significantly ineffective in the deeper stromal regions of the cornea.
This is a 2020 ARVO Annual Meeting abstract.