A Coupled Bioheat Transfer Model for Customized Whole-Eye Modeling in Retinal Laser Surgery

The photothermal effects of laser on tissue are widely used in ophthalmology to treat retinal diseases. The multiscale retinal lesion from the micrometer size to the millimeter size can be thermally targeted by adjusting the pulse duration from nanoseconds to tens of seconds. A large-scale difference among target lesions has brought extra challenge for retinal laser surgery modeling. In this study, we developed a coupled whole-eye model for retinal laser surgery. In the model, the Pennes bioheat transfer equation was adapted for the whole-eye temperature modeling. Simultaneously, we treated the fundus as a multilayered porous medium made of a tissue matrix buried with highly absorbing chromophores (melanin or blood). Two-temperature equations, one for the chromophore and the other for the surrounding tissue, were developed on the basis of the local thermal nonequilibrium theory of porous media. The Pennes and two-temperature models were coupled together to calculate the thermal responses of eye during several laser retinal surgery processes with pulse duration from nanoseconds to tens of seconds. Simulation results proved that our model was capable of modeling the laser retinal surgery process at different time scales. Furthermore, the coupled model was applied in a real fundus anatomy from a patient with diabetic retinopathy to illustrate its feasibility in customized laser protocol planning.