Physical modelling to assess the effect of micropulse modes of laser radiation at the chorioretinal complex of the human eye based on the theory of activated complex

Abstract

Purpose: to construct a physical model based on the theory of activated complex (TAC) with indicators ΔH and ΔS mentioned in works of G.I. Zheltov and his colleagues so as to assess the impact of laser radiation micropulse modes at the chorioretinal complex (CRC), as well as to compare it with models based on the Arrhenius integral and with results of micropulse mode testing using autofluorescence method.Material and methods. Modeling of the degree of damage to CRC and adjacent structures was carried out using Eyring equation. Values of ΔH = 360 000 J/mol and ΔS = 890 J/mol·deg for complex of proteins and other RPE organic structures were determined by G.I. Zheltov and co-authors in vivo in a series of laser experiments on primates. For modeling, absorption coefficient of 460 cm–1 was used, for wavelength 577 nm – 10-micron-thick RPE layer and transmission 37 %. Micropulse mode testing (50 μs, 2.4 %, 10 ms, 100 mkm, 0.4–1.9 W) was performed using Navilas 577s navigation laser in patients aged 35–46 with appearance of types 2–3 by the Fitzpatrick scale; results of this testing were assessed using short-wave autofluorescence (488 nm) method.Results. A physical model based on TAC and Eyring integral was constructed. Results of modeling of the degree of RPE injury depending on power coincide with the results of testing of micropulse mode in patients according to autofluorescence method. The average RPE absorption coefficient equal to 440 cm–1 for patients aged 35–46 years and with appearance of type 2–3 by the Fitzpatrick scale was clarified.Conclusion. The computer modeling based on TAC using the Eyring equation with ΔH and ΔS for a complex of proteins and other RPE organic structures, which are described in works of G.I. Zheltov and his co-authors, has shown a high degree of compliance with the results of micro-pulse mode testing in real patients. Modeling does not require adjustment of any free parameters unlike approaches based on the Arrhenius equation; it also allows to find absorption coefficients for a small sample of patients and to assess the level of laser radiation damage to RPE and adjacent structures.