Anna A. Gavrilova

Optical clearing of human eye sclera under the action of glucose solution

We present experimental results of investigation of the optical properties of the human eye sclera controlled by administration of osmotically active chemical, such as 40%-glucose solution. Administration of the chemical agent induces diffusion of matter and as a result equalization of the refractive indices of collagen and ground material. Results of the experimental study of influence of the glucose solution on the absorption and scattering properties of human sclera are presented. In vitro reflectance and transmittance spectra of the human sclera samples were measured by commercially available spectrophotometer CARY-2415 in the spectral range from 400 to 1800 nm. The reduced scattering coefficient of human sclera samples is significantly decreased under action of the osmotical solution were demonstrated.

Enhanced optical clearing of human skin at topical application of immersion agents to stratum corneum pretreated by a lattice-like photothermal ablation

High level of light scattering in mammalian skin significantly deteriorates the effectiveness and precision of light delivery to intra- and subcutaneous targets in therapeutic and diagnostic applications. Optical immersion based on the refractive index matching of tissue scattering centers with surrounding matter via introduction of an exogenous indexmatching agent is capable to alleviate the problem. But this process goes slowly enough because of sluggish diffusion of various immersion agents through a stratum corneum (SC) barrier, making a practical realization of this approach difficult. In order to increase the rate of the process we designed the method of accelerating the penetration of optical clearing agents (OCAs) by enhancing skin permeability through a creation of lattice-like pattern of localized thermal damage (ablation) islets in the SC. OCAs, such as glucose, propylene glycol, and glycerol solutions, were applied. Experimental results show a remarkable increase in the rate of optical clearing. The most of results were obtained on in vivo human skin.

Skin spectrophotometry under the islet photothermal effect on the epidermal permeability

The results of experimental investigation of an increase in the epidermal barrier permeability are presented. The results are obtained using the method based on the creation of permeability microzones (islets) during the local thermal action on stratum corneum. It is shown that the epidermal barrier permeability considerably increases under the island photothermal effect and application of various clearing agents. Detailed spectrophotometric investigations of skin under the conditions of a partial violation of the epidermis barrier functions due to the island effect and introduction of various immersion agents in the skin are presented. The effect of various conditions of the object illumination on the dynamics of spectra is analyzed. A common behavior of the dynamics of the spectra of all kinds during clearing is revealed. Possible mechanisms accompanying the optical clearing process under the island photothermal effect are discussed.

Skin optical clearing for improvement of laser tattoo removal

The removal of tattoo pigments by laser energy is effected through a process of selective photothermolysis. Dehydration and optical immersion based on refractive index matching of scattering centers with that of surrounding matter through introduction of an exogenous index-matching agent can improve laser tattoo removal by providing increased efficiency of laser delivery to embedded ink particles and enabling the use of shorter wavelength visible lasers more effective on certain inks. Effectiveness of a method of accelerating penetration of the index-matching compounds by enhancing skin permeability through creating a lattice of micro-zones of limited thermal damage in the stratum corneum was studied. As optical clearing agents 100% and 88%-aqueous glycerol solutions were used. The effect of stratum corneum perforation on the rate of the immersion clearing of skin was studied. Dynamics of refractive index alteration of glycerol solution during its interaction with skin samples was monitored. Improvement of tattoo visualization was observed. The results of the experiments have shown that the lattice of island damage method the is effective for transepidermal delivery of optical clearing agents and could be used successfully in in vivo conditions for the enhancement of optical clearing of treated skin area and as enabling improvement of laser tattoo removal.

Mechanisms of in vivo optical clearing of human skin at application of glycerol and lattice-like photothermal damage of stratum corneum

Controlling of optical properties of skin is of great interest for skin diseases monitoring and phototherapy. Glycerol, as the most effective optical clearing agent, was applied in this study. Effects of osmotic properties of glycerol on optical clearing of the human skin have been investigated. Two main mechanisms of optical clearing at a creation of lattice-like pattern of localized thermal damage islets in the SC, glycerol diffusion into damaged skin and tissue dehydration, were discussed.

Preliminary investigations in vitro optical clearing of rat skin using island damage method for accelerated delivery of index-matching agents

Strong light scattering in skin prevents precise targeting of optical energy in therapeutic and diagnostic applications. Optical immersion based on matching refractive mdcx of scattering centers with that of surrounding matter through introduction of an exogenous index-matching agent can alleviate the problem. However, slow diffusion of the index-matching agent through skin barrier makes practical implementation of this approach difficult. We propose a method of accelerating penetration of the index-matching compounds by enhancing skin permeability through creating a lattice of micro-zones (islets) of limited thermal damage in the stratum comeum. Two index-matching agents, glucose and glycerol, were tested. Glycerol used as index-matching agent gave noticeably better clearance then 40% glucose solution.

Study of relaxation of thermally treated collagenous tissues with the cumulant analysis of speckle intensity fluctuations

The possibilities of characterization of the relaxation processes in thermally treated collagenous tissues with the use of the cumulant analysis of speckle intensity fluctuations are discussed. This method deals with the correlation analysis of spatial-temporal fluctuations of laser light multiply scattered by thermally modified tissue under the condition of polarization discrimination of detected speckle-modulated optical signals. Experimental results, which were obtained with ex-vivo cartilage samples, are presented.