First-order model of thermal lensing in a virtual eye

Area of Science:

• Optics and Photonics
• Biomedical Engineering
• Laser Physics

Background:

• The thermal lens effect, induced by laser absorption, can impact biological tissues.
• Understanding this effect is critical for assessing laser safety, particularly in ocular applications.
• Previous models often lack detailed physiological simulation or precise thermo-optic coefficient integration.

Purpose of the Study:

• To develop a first-order mathematical model of the thermal lens effect in ocular media using near-infrared lasers.
• To determine the thermo-optic coefficient (dn/dT) of water at physiological temperatures.
• To simulate the transient thermal lens response within a human eye model and assess proximity to retinal damage thresholds.

Main Methods:

• Utilized the ABCD beam-propagation method for mathematical modeling.
• Fitted the model to experimental z-scan data to determine the thermo-optic coefficient of water.
• Incorporated physiological parameters of the human eye into a simplified eye model.
• Simulated laser-induced thermal lens effects for 1150 nm and 1318 nm laser radiation.

Main Results:

• The model accurately predicted experimental data with a thermo-optic coefficient for water of -4.46x10⁻⁵ K⁻¹ at 292 K.
• Simulations demonstrated the transient thermal lens formation in ocular media.
• The study illustrated the approach of these thermal effects towards retinal damage thresholds.

Conclusions:

• The developed mathematical model provides a valuable tool for understanding laser-tissue interactions.
• Accurate thermo-optic coefficients are essential for reliable thermal lens effect predictions in biological systems.
• The findings contribute to establishing safety limits for near-infrared laser exposure to the human eye.