Age-dependency of Cornea Biomechanics Measured by OCT Vibrography: A Pilot Study

The cornea, the clear front window of the eye, consists of finely intertwined collagen fibers, which give the cornea a microstructure that provides mechanical integrity necessary to maintain its typical dome-shape against the intraocular pressure (IOP). Changes in the biomechanical properties can lead to an abnormal corneal shape and refractive errors. As a result, light is not perfectly focused onto the retina and the vision is affected. A typical example of alterations in the cornea's biomechanical properties is found in patients with an eye disorder called Keratoconus, which leads to progressive thinning of the cornea. Numerous studies have shown that promising interventions like collagen crosslinking (CXL) can slow down an arrest progression of ectatic eye diseases. Keratoconus, as a typical example, although it cannot be cured, could be at least halted by CXL. Therefore, early diagnosis of ectasia is crucial for the patient. Current diagnostic methods of ectasia are based on morphological rather than biomechanical analysis. The irregular patterns of the cornea can be detected by pachymetry and topography before clinical signs occur, but these tests cannot reliably differentiate truly weak or keratoconic corneas from atypical normal ones.

These are compelling needs for improved diagnostic methods. More recently, and triggered by those unmet needs, an interest in the mechanical properties of the cornea has emerged. Typical examples of mechanical properties are elastic modulus and corneal stiffness.

In this pilot study the investigators will test the ability of a new OCT Vibrography system to determine cornea material parameters. More precisely, the investigators will study the oscillation response in human corneas in-vivo using a stimulus mechanism used to induce vibrations by touching the surface of the cornea. A localized vibration source paired together with phase-sensitive OCT to measure the frequency response function of the human cornea and to analyze the dependency of the frequency response function on age. Additionally the investigators will use Brillouin Microscopy data for computer simulations to validate OCT Vibrography results.