Laser-induced modification of the scleral collagen framework for changing its hydraulic permeability

An action of the IR laser pulses with a wavelength of 1.56 μm, moderate intensity, and various durations on a collagen framework structure and sclera tissue permeability is considered. It is shown that the temperature thresholds of collagen denaturation in tissues under the laser irradiation are substantially lower as compared to those under conventional homogeneous heating in a calorimeter oven. A tissue matrix modified at temperatures below the denaturation threshold is observed in images obtained by nonlinear optical microscopy in the regime of second harmonic generation. The modification has specific features under long-duration (with a duration longer than 1 s) and short-duration (10 – 30 ms) action: separation of a fibre bundle into groups with distorted passage in the first case and bundle splitting to chaotically directed fibres in the second case. The character of the tissue change determines the coefficient of organic substance diffusion into a tissue material. After matrix amorphisation (collagen denaturation) or distortion of the fibre group arrangement in the collagen bundle, the diffusion coefficient falls by 10 % – 40 %, whereas after bundle splitting it increases by 25 % – 50 % as compared to the value of (3 ± 0.1) × 10⁻⁶ cm s⁻¹, which is specific for intact tissue. The results obtained make us to assume that the specific disordering of the tissue collagen framework under the short-duration action may be used for increasing the permeability of the scleral tissue.