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.
Laser surgery of the changing cartilage shape is based on photothermal effect on tissue components, which leads to its plasticization and, consequently, reshaping of this tissue. With the rapid laser heating, an optoacoustic wave is generated in the tissue, by the propagation and amplitude of which one can understand the changes in the mechanical properties of the tissue. In this work, data were obtained on the relative time variation of the mechanical stresses of the cartilage tissue upon heating and its temporal characteristics (relaxation time and system response time). A simultaneous recording of the electrical conductivity response of the cartilaginous tissue and mechanical stresses on a pulsed - periodic laser exposure is presented. As a result of this study, it was found that the mechanical stresses in the tissue are in good agreement with the electrical response of the tissue and a drop in resistance. It has been found that the continuation of tissue impedance falling down after the laser exposure switched off causes relaxation of the internal stresses. These studies are the base for the development of a control system for laser operations on cartilage tissue.
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