Laser-optical methods for monitoring the biomechanical properties of the anterior part of the eye

Abstract

Biomechanics of eye tissues is an important parameter of the state of the ocular system and its study is of undoubted interest since there are several clinical situations in which an in vivo assessment of mechanical properties can help both in diagnosis and in treatment. The risk of developing glaucoma and keratoconus of the eye is associated with pathological changes in the biomechanical properties of such eye tissues as the cornea and sclera. Thus, the problem arises of studying tissue biomechanics and the possibility of influencing it. For this purpose, experiments were carried out to determine the dynamics of elastic properties of intact and modified tissue of the sclera and cornea of the pig's eye by OCT elastography and speckle interferometry. Internal stresses found by numerical simulation from a comparison of subsequent OCT frames demonstrate a dependence on the biomechanics of the tissue sample. It was also shown that the time and temperature dependences of the contrast and correlation functions in speckle interferometry make it possible to track the onset of structural changes in the tissues during repetitively pulsed laser heating. A comparison was made in the behaviour of these curves for the central and peripheral regions of the cornea. The results obtained and their repeatability allow us to conclude that the speckle interferometry can be used as the basis for a system for monitoring structural changes in the cornea associated with the thermal effect of laser radiation. OCT elastography is a sensitive method for studying the biomechanical properties of eye tissues (cornea and sclera) under laser exposure, reflecting the dependence on the intraocular pressure of the eye. This method can be used as the basis for a control system in the development of medical technology for influencing the sclera and cornea of the eye.