An ABCD beam-propagation method was used to build a first-order mathematical model of a thermal lens effect from a near-infrared laser beam in water and ocular media. The model was found to fit experimental z-scan data best when the thermo-optic coefficient dn/dT of liquid water at 292 K was -4.46x10(-5) K(-1). The physiological parameters of the human eye were simulated in a simple eye model using this fitted dn/dT value. Conservative model simulations for 1150 and 1318 nm laser radiation include parameter sets used in experimental ocular exposures performed by Zuclich et al. [Health Phys.92, 15 (2007)] to illustrate the transient response of the thermal lens approaching the limits of the retinal damage thresholds for equivalent laser radiation sources.