Three-dimensional bio-heat transfer simulation of sequential and simultaneous retinal laser irradiation

Transient simulation of retinal laser irradiation is performed for a square array comprising 3 × 3 uniformly distributed spots under sequential and simultaneous mode. A finite volume formulation of the Pennes bio-heat transfer model is employed as the governing equation to generate the temperature distribution within the eye domain. Temperature distribution developed due to laser power of 0.2 W/spot and time duration of 100 ms/spot is used to compare the merits of sequential and simultaneous irradiation of spots. Simultaneous mode is preferred when the time of surgery is limited, with possible excess heating in the inter-spot retinal regions. The inter-spot spacing D is also varied between one diameter and one and half diameter of the spot size (diameter) to evaluate the safe placement of consecutive spots. D ≥ 0.75 mm can be considered as the optimum spot distance for non-interference due to excess heating. Effect of pulsation of incident laser power is observed to favorably reduce the average temperature of the irradiated regions of the retina toward photocoagulation temperature.