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In recent years, an emerging group of therapeutic methods, which can be considered as intermediate between photobiomodulation and coagulative methods, is non-surgical thermo-mechanical reshaping of avascular collagenous biological tissues. It is based on moderate laser-produced heating (below 50-70°C) combined with auxiliary mechanical action on the tissue. For duly chosen parameters, such moderate heating can be biologically non-destructive, so that this technique of laser-assisted modification of collagenous tissues is emerging in clinic for various applications. For example, using such an approach, planar cartilaginous plates can be transformed into annulus-shape implants for otolaryngological operations. Similar microstructural changes occurring in moderately heated cornea open the possibility to modify eye-cornea shape and, consequently, eye refraction, which can be used for non-surgical correction of vision problems. Such applications obviously require detailed understanding of the background thermo-mechanical properties and possibility to precisely control the laser-produced heating and the resultant deformations of the tissue. Recently, progress in the development of optical coherence elastography (OCE), in particular the possibility to obtain high-resolution maps of "instantaneous" and cumulative strains suggests that OCE can be successfully used as a control mean in the novel applications of laser-assisted tissue reshaping. This study reports results on application of phase-sensitive optical coherence elastography for mapping transient thermomechanically-produced strain fields in such biological tissues, as cartilages and cornea subjected to pulse-periodic irradiation with infrared Gaussian laser beam. The developed OCE technique made it possible to demonstrate complex character of the thermo-mechanically produced strains, which is attributed to non-trivial interplay between the spatially non-coinciding temperature increase and thermal stresses.
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