Optimum asymmetric spatial and temporal distribution of femtosecond laser pulses in refractive surgery

Femtosecond laser-assisted refractive correction relies on temporally and spatially separated pulses that generate coalescent cavitation bubbles, forming a cleavage plane for tissue separation. Achieving optimal outcomes requires balancing laser-induced stress, mechanical dissection stress, and surface roughness. This work introduces a nonlinear absorption model and a theoretical framework to identify the optimum spatial and temporal distribution of single pulses. The analysis, based on inequalities involving scaling factors for spot size and track distance, defines a bounded solution space. Within this domain, the most favorable setting corresponds to minimum dose with maximum asymmetry, ensuring energy efficiency while enhancing surface smoothness, whereas the least advantageous of the optimum conditions occurs for higher dose and minimum asymmetry (compatible with optimum conditions), both enabling a theoretical bridge-free dissection. Bubble overlap emerges as a key determinant of cutting efficiency and smoothness, and an optimal window for overlap factors is delineated, minimizing treatment dose while preserving corneal quality through smoother stromal cuts.