Study of the possibility of increasing the intensity of photochemical processes of riboflavin/UV photocrosslinking of scleral collagen by means of tissue immersion clearing

The possibility of increasing the efficiency of light action during scleral collagen riboflavin/UV photocrosslinking by means of immersion clearing of tissue before UV irradiation is studied. The effectiveness of photo-action is assessed by a decrease in the relative content of the photocrosslinking sensitizer, riboflavin, which is determined from the decay times of tissue fluorescence at different stages of the photocrosslinking process. The fluorescence decay times are measured using a multiphoton tomograph in the mode of time-resolved two-photon fluorescence recording. Studies are performed in vitro on porcine sclera samples. An 88% aqueous solution of glycerol is used as an immersion clearing agent. Optical clearing is shown to make it possible to increase the intensity of photoinduced conversion of riboflavin into non-fluorescent leukoforms during photochemical reactions preceding collagen crosslinking. According to the experimental data obtained for cases of photocrosslinking without optical clearing and with preliminary optical clearing of tissue under the same irradiation conditions, the content of riboflavin that has not undergone photoconversion in tissue, at depths from 40 to 75 mm, after UV irradiation in the first case is approximately 5.6 times (average over 15 regions of two samples) higher than in the second case.