Determination of modes for safe application of selective micro-pulse individual retinal therapy of the macular zone using the modeling based on the theory of activated complex

Abstract

Purpose: to make modeling of various modes of laser radiation, to assess the degree of damage to the retinal pigment epithelium and adjacent structures, and to determine modes and safety conditions of selective micro-pulse individual retinal therapy based on the theory of activated complex. Materials and methods. The authors have modeled the degree of damage to the chorioretinal complex and adjacent structures using the activated complex theory with the Eyring equation. The following definitions were used to determine the regime quality and safety conditions: micro-pulse mode is a mode with fixed values of micro-pulse duration, duty cycle and the number of pulses in the packet; power is a variable parameter. Efficiency is the ratio of the amount of denatured protein inside the retinal pigment epithelium layer to the total amount of protein in it. Selectivity is the ratio of the amount of denatured protein inside the retinal pigment epithelium layer to the total amount of denatured protein. Relative harmfulness is the ratio of denatured protein volume outside the retinal pigment epithelium to the volume of protein in it. Results and discussion. The quality of micro-pulse mode was found as depending on the selectivity value with efficiency equal to 90 %. With the efficiency value less than 50 %, the mode is non-selective, with more than 67 % – selective. Safety conditions for selective micro-pulse modes have been established, taking into account safety of the neurosensory retina and choroid in terms of relative harmfulness which should not exceed 1. Parameters at which micro-pulse modes have high values (more than 90 – 99) of efficiency and selectivity at the same time have been determined as well. It requires single pulse mode, micro pulse duration of 25 microseconds and power from 6 to 8 W. To expand the combination of parameters, it is necessary to be able to freely change them in increments of 1 pulse, 5 microseconds, 100 mW, with long interval and short duty cycle. These technical capabilities can be realized and implemented into clinical practice by manufacturers of laser devices. Conclusion. For selective micro-pulse individual retinal therapy of the macular zone with existing lasers, the following recommendation are to be observed: micro-pulse modes with pulse duration no more than 200 microseconds, short duty cycle less than 5 % and number of pulses in an envelope no more than 5; relative harmfulness less than one, radiation power selection, personalized patient’s characteristics.