Abstract
Purpose :
Laser-based surgery gains importance and techniques in refractive surgery are improved. The femtosecond laser plays an important role in this field leading to fewer complications during and after surgery and a more precise cut. The aim of this work is to simulate an idealized/simplified cutting surface of such a system based on laser induced optical breakdown (LIOB).
Methods :
The algorithm considers a possible trajectory of the laser pulses and calculates the roughness for different parameter settings (including LIOB threshold, pulse energies, and spot spacings). Certain critical points are considered (such as treatment dose) and the difference between achieved and ideal cut determines the roughness. Specific variables, such as spot distance (along the pathway), track distance (between lines/tracks) and pulse energy, are iteratively optimized.
Results :
Analyses support the following findings for reducing roughness of the cut:
Tighter pulses (spacings) using constant pulse energies lead to lower roughness
Lower pulse energies for the same dose lead to lower roughness
Asymmetric settings with spot distance larger than track distance, for the same pulse energies and treatment dose, lead to lower roughness
Lower pulse energies are more important than asymmetric settings
Conclusions :
Simulations suggest that lower pulse energies (well above LIOB threshold) combined with asymmetric spacings (spot-to-track distance ratio >>1) may be effective to lower the roughness of laser cuts generated by LIOB processes. Lower pulse energies (well above the threshold) emphasize the need for the LIOBTh to remain as low as possible. Reducing roughness by decreasing spacings (higher dose for same pulse energies) may have negative implications in visual recovery (risk for overdose). The optimized roughness is multiple times larger (rougher) than equivalent simulations for ablative procedures.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.