# Laser Processing of Intraocular Lenses
## 4 Discussion and Conclusions
The roughness of femtosecond laser-induced micro-patterns can vary significantly with different laser powers. Higher laser power increases the energy delivered to the material, resulting in deeper ablation and potentially greater surface roughness due to more destructive material removal. For example, in a previous work [44], [PERSON] et al. used for PMMA sample patterning a femtosecond laser at 1030 nm with a pulse duration of 240 fs and repetition rate of 610 kHz. It was found that at lower pulse energy (0.4 um) and a scanning speed of 1 mm/s, the patterning resulted in ripple-like microstructures. In contrast, higher pulse energies (0.8 um and 1.2 um) at the same speed led to the formation of bumps and pores. Increasing the scanning speeds to 2 mm/s and 8 mm/s reduced the groove width but increased surface roughness due to the presence of microparticles. Theseeffects are also observed at high repetition rates and low scanning speeds, where the pulse energy is much higher than the ablation threshold, leading to significant heat accumulation. Therefore, as demonstrated in our work, a careful selection of writing parameters is needed for efficient patterning with reduced roughness. Furthermore, it could be noted that in the same aforementioned work, smoothing of femtosecond laser-machined PMMA surfaces was attempted by thermal annealing treatment at 160 \({}^{\circ}\)C for various time intervals, thus considerably improving the roughness. Although this technique was not investigated in PMMA or acrylic IOLs in our work, it could be considered in future studies provided that IOLs can withstand such a thermal annealing process. Each laser system has its unique interaction mechanism with the target material, and selecting the most appropriate one based on the desired outcome is crucial. Specifically with femtosecond lasers, we leverage multiphoton absorption, enabling us to pattern materials that do not readily absorb at the laser's wavelength. However, both PMMA and acrylic IOLs exhibit significant absorption in the 355 nm (nanosecond laser) and 405 nm (diode laser) ranges and although this enhances the efficiency of the inscription process at the surface, adaptive focusing is required for patterning beneath the material's surface and at various depths, making the process quite challenging. Another technical issue to address in future studies is the challenge of maintaining and accurately controlling the required focus during the laser writing process on the curved surfaces of IOLs. The inclusion of rotational translation stages in the micromachining station, along with a dynamic autofocus system, will significantly enhance the precision and accuracy of IOL patterning. Further exhaustive studies are required for the development of accurate IOL patterning approaches, based on the current findings, that would be compatible with IOL surface tailoring based on corneal wavefront data, enabling personalized vision correction solutions and enhancing patient outcomes in cataract surgery. Conceptualization, C.B., M.K. and C.R. ; methodology, M.K. and C.R. ; validation, M.K., C.R., A.S. and C.B. ; formal analysis, A.S., D.P., C.R., M.K. and D.M. ; resources, D.M. and D.P. ; investigation, A.S., D.P., C.R., M.K., C.B. and D.M. ; writing--original draft preparation, A.S., D.P., C.R. and M.K. ; writing--review and editing, A.S., M.K., D.P., C.B., D.M. and C.R. ; supervision, M.K. and C.R. ; project administration, M.K. and C.R. ; funding acquisition, M.K. and C.R. All authors have read and agreed to the published version of the manuscript. This research work was supported by the Hellenic Foundation for Research and Innovation (H.F.R.I.) under the \"First Call for H.F.R.I. Research Projects to support Faculty members and Researchers and the procurement of high-cost research equipment grant\" (Project Number: HFRI-FM17-640, InPhoQuC). Not applicable. The original contributions presented in the study are included in the article; further inquiries can be directed to the corresponding author.