Dependence of Corneal Collagen Crosslinking Tensile Stiffening on Hydration Level

The refractive power of the eye determines how clear our vision is. Cornea, which is the outermost layer of the eye, allows the light to pass through it. In conjunction with the lens, it focuses the incoming light on to the retina, giving the eye its refractive power. Additionally, being the peripheral layer, it protects the intraocular components. Consequently, it is susceptible to both internal and external damage. Keratoconus is an ectatic corneal disease, which results in progressive thinning of the corneal tissue. It causes distortion in vision with complications such as blurry vision, seeing multiple images of the same object and irregular astigmatism. Treating keratoconus depends on the stage of the disease; basic intermediate and advanced. In the most advanced stage, corneal transplantation is used to replace the diseased tissue. Despite having success rates of up to 93%, factors such as patient’s age, trauma and health of the donor tissue may contribute to tissue rejection. Over the last decade, UV corneal crosslinking, an alternative treatment, has shown its potency in stopping the progressive bulging of keratoconic cornea. It has been proven to increase the stiffness of cornea by induction of crosslinks inside the corneal stroma when the tissue soaked in photosensitizer solution is exposed to UV radiations. Since its inception, there have been modification and improvements made in the crosslinking protocol including, but not limited to, decreasing the total treatment time and swelling the tissue prior to crosslinking. Such changes result in the variation of hydration level of the tissue prior to crosslinking. In this study, the effect of hydration level of crosslinking on the mechanical properties of the crosslinked cornea has been studied by performing uniaxial tensile tests on the crosslinked corneas. The findings from this study improves the understanding of the effectiveness of UV corneal collagen crosslinking treatment and opens new window of opportunity in the research field of corneal crosslinking.