# Laser Processing of Intraocular Lenses
## 4 Discussion and Conclusions  
This study presents a preliminary comparative analysis on the feasibility and efficacy of using direct laser-based micromachining technology with various characteristic lasers to modify IOLs' surfaces. The ultimate scope of this work is to be employed and optimized in future studies in order to achieve customizable vision correction solutions  
Figure 12: Raman spectra of acrylic IOLs before and after laser ablation with femtosecond 1064 nm and CW 405 nm lasers. (**a**) Regular; (**b**) confocal micro-Raman spectra. based on relevant corneal wavefront data. The correction depth in customized IOL ranges typically from 0.2 um to 3 um, depending on the refractive error and the patients' visual correction preferences. Our research revealed that infrared femtosecond 1064 nm laser ablation can produce 2D controlled patterns on PMMA IOLs within the range of a few micrometers and could be adapted to meet the required correction depths. Indeed, the micromachining process exhibited sensitivity to various laser parameters such as the repetition rate, pulse energy, and focus, affecting ablation depth and pattern uniformity, as observed with the acrylic IOL irradiation, thus providing the required flexibility. By considering the ablative laser modifications in relation to underlying thermal processes attributed to laser pulse cumulative heating, optimal laser operation regimes for the femtosecond laser were identified, providing improved micromachining performance compared to previous studies. More specifically, the employed Yb-based fiber laser at 1064 nm was operated at a 100 KHz repetition rate and thus adapted to heat diffusion time in polymer IOLs in order to eliminate heat accumulation during laser writing that could lead to discontinuous features as in previous studies. Nanosecond 355 nm laser ablation effectively produced larger ablation areas, typically within the range of hundredths of micrometers, on acrylic IOLs and also exhibited sensitivity to exposure time, leading to variations in crater dimensions and structural changes within the IOLs. However, due to very low resolution and inadequate control in low-depth features (<2 um), the nanosecond lasers cannot be considered as a good candidate for IOL patterning. Our investigation with the CW 405 nm diode laser showcased its precision in modifying acrylic IOLs, despite the challenges in pattern generation due to exposure configuration and increased power requirements for PMMA IOLs. Notably, our study marks the first application of low-cost CW diode lasers for IOL surface modification, indicating promising prospects for laser ablation procedures in IOL customization. Raman spectroscopy was extensively employed for the post-laser treatment characterization of structural integrity of the IOLs, for the case of femtosecond and CW diode laser patterning. Although typical micro-Raman did not identify significant structural changes, the application of confocal Raman spectroscopy, for the case of the femtosecond 1064 nm laser treatment of the acrylic lens, revealed the existence of relevant peaks attributed to amorphous carbon at the IOL surface layer only. However, this degradation needs to be further quantified and characterized in terms of the optical deterioration of IOL, in order to extract a safe conclusion on the effect of femtosecond laser patterning in functional characteristics of IOLs. On the other hand, no measurable degradation of IOLs was identified for diode laser patterning, suggesting another favorable characteristic for this patterning approach. The differences observed in the outcomes of laser ablation between PMMA and acrylic IOLs can be attributed to variations in their material properties, including thermal conductivity, melting point, and absorption coefficients, among others. By systematically varying parameters such as laser energy, repetition rate, scanning speed, and focus position, the laser ablation process will be optimized for both IOLs under irradiation with different laser systems.