Nonuniform laser heating affects the porous system of biological tissues. Formation of new pores in the paralimbal region of the eye can accelerate the flow of the intraocular fluid through the eye sclera and, thus, facilitate normalization of the intraocular pressure. A positive effect of laser impact is achieved, as a rule, in a narrow range of laser radiation parameters, which makes it difficult to choose the intensity and time parameters of laser irradiation due to such factors as nonstationary temperature fields, thermotensions and pressure that can give rise to undesirable effects and complications.
The comparison between reflected and transmitted laser light through the eye tissue has allowed to establish the main requirements for laser settings parameters responsible for efficacy and safety of the laser irradiation. The positive effect is achieved only by using relatively small intensity of the laser radiation. At high intensity, the hydraulic permeability decreases due to denaturation and tissue hardening.
Atomic Force Microscopy (AFM) measurements with nanoindentation and optical coherence tomography (OCT) based compressional phase-sensitive optical coherence elastography (OCE). OCE measurements demonstrated laser-induced dilatation areas attributed to formation of ensembles of micro-and nano-pores in sclera providing increase in its hydraulic permeability. Much higher resolution AFM examinations directly demonstrated such individual irradiation-produced pores. At the same time, the collagen structure of the sclera is not destroyed, and tissue mechanical properties do not degrade under laser radiation. The process of pore formation is in good agreement with computer simulations of the dynamics of thermal stress fields induced by laser irradiation.