Numerical simulation of ophthalmic laser surgeries by a local thermal non-equilibrium two-temperature model

Bin Chen (State Key Laboratory of Multiphase Flow, Xi’an Jiaotong University, Xi’an, China)
Yibo Zhao (State Key Laboratory of Multiphase Flow, Xi’an Jiaotong University, Xi’an, China)
Dong Li (State Key Laboratory of Multiphase Flow, Xi’an Jiaotong University, Xi’an, China)

International Journal of Numerical Methods for Heat & Fluid Flow

ISSN: 0961-5539

Publication date: 24 July 2019

Abstract

Purpose

This paper aims to understand the laser–tissue interaction mechanism during ophthalmic laser surgeries through numerical analysis. The influence of laser parameters and the multipulse technique were investigated.

Design/methodology/approach

The ocular fundus was simplified as a multilayered homogenous medium model. Afterward, the multilayer Monte Carlo method was used to simulate the propagation and energy deposition of laser light, and a local thermal non-equilibrium two-temperature model was established to simulate the temperature variation of chromophores and surrounding tissue with different laser wavelength.

Findings

Through the model, the selective heating of chromophore (melanin and blood vessels) was clearly illustrated: 1) neglecting the laser energy absorbance by blood in the traditional model will cause significant errors in temperature calculation; 2) the non-thermal equilibrium heat transfer model was needed to obtain an accurate description of the thermal process when the dimensionless pulse width (tp*) is <105. For 532 nm Argon laser, the optimize tp* is around 105 and the appropriate energy density is 5 J/cm2; 3) multipulse technique makes the energy more concentrated within the melanin, thereby reducing the thermal damage in surrounding tissue, with most appropriate pulse number and duty cycle is 10 and 1/10.

Originality/value

Taking the blood absorption into account, the different temperature variations of melanin/vessels and surrounding tissue caused by the selective photo-thermolysis were simulated successfully. By understanding the mechanism of laser therapy, laser parameters and multipulse technique are suggested to improve the clinical results.

Keywords

Citation

Chen, B., Zhao, Y. and Li, D. (2019), "Numerical simulation of ophthalmic laser surgeries by a local thermal non-equilibrium two-temperature model", International Journal of Numerical Methods for Heat & Fluid Flow, Vol. ahead-of-print No. ahead-of-print. https://doi.org/10.1108/HFF-05-2019-0397

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Publisher

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Emerald Publishing Limited

Copyright © 2019, Emerald Publishing Limited

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