Periodic Reporting for period 1 - LasInPOP (Direct Laser Interference Patterning of Ophthalmic Polymers) Reporting period: 2019-04-01 to 2021-03-31 Summary of the context and overall objectives of the project To date main photo-refractive techniques used to correct refractive errors use UV laser radiation to reshape corneal tissue through photo-ablative decomposition processes. These techniques are destructive, invasive, and irreversible and may entail postsurgical complications and secondary visual effects such as dry eye, irregular astigmatism, stromal haze, and corneal ectasia. Refractive errors are the first cause of visual impairment and the second cause of visual loss worldwide. Uncorrected refractive errors were responsible for visual impairment in 101.2 million people and blindness in 6.8 million people in 2010.The general aim of this project is to use Direct Laser Interference Patterning to be applied for refractive correction in ophthalmic polymers. Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far Direct Laser Interference Patterning (DLIP) was used to modify poly-hydroxyethyl-methacrylate (PHEMA) polymers and Safrofilcon-A hydrogels. These polymers are commonly used as soft contact lenses. The structuring process was carried out by using pulsed laser sources emitting at laser wavelengths in the UV-Visible range and pulse duration in the pico-second and nano-second range. Laser features and optical configuration was modified to achieve optimal structuring conditions. Also, these polymers were structured by using Direct Laser Writing (DLW) to compare both laser structuring techniques. Topography of the structured areas was evaluated by means of confocal microscopy, and micro-Raman spectroscopy was used to assess the microestructural and chemical properties of the laser-structured areas. Finally, optical characterization was carried out in the processed areas to evaluate the modification of the refractive index. DLIP was found to be more efficient, resulting in refractive index changes up to one order of magnitude higher than those obtained by using DLW. In addition, the processing time to produce the structured areas by using DLIP was nearly 3 orders of magnitude faster than using DLW. Hydration properties of DLIP-structured areas were evaluated by using static water contact angle (WCA) measurements with deionized water droplets. Hydration process was found to be similar to non-structured areas.Results were disseminated in international conferences such as E-MRS Spring Meeting 2019, LPM 2020, and MSE 2020, and published in international journals such as Applied Sciences, Polymers, Proceedings of the LPM2020, and Journal of Laser Micro/Nanoengineering. Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far) DLIP was successfully applied to manufacture diffraction gratings on the surface of ophthalmic polymers. These results are the first step towards the development of a novel laser processing technique to be applied for the correction of refractive errors in ocular tissues. Refractive index change achieved in the laser-structured areas ranged 1×10-2, one order of magnitude higher than those achieved by Direct Laser Writing (DLW). In addition, processing speed was found to be nearly three orders of magnitude faster than the reported by DLW. figure-summary.jpg
