Laser induced refractive index change (LIRIC) technique has been demonstrated as a non-invasive way to alter opticalrefractive powers of ophthalmic materials including hydrogel-based contact lenses, exercised corneal tissues and evencorneas in vivo, via modifying the refractive index through multiphoton absorption process. In our previous work, bluefemtosecond laser pulses at 405 nm with a repetition rate of 80 MHz were focused tightly into the stromal region to achieverefractive corrections in live cats via inscribing phase wrapped structures. In order to improve the efficacy of LIRIC, wehere demonstrate that blue femtosecond laser pulses at a lower repetition rate range induce larger amounts of phase changewith lower laser powers and higher scan speeds owing to a higher pulse energy density deposition. In comparison to a highrepetition rate writing at 80 MHz, higher phase change can be attained at 8.3 MHz at the same average power. Furthermore,one wave of phase change measured at 543 nm was attained in rabbit corneas ex vivo for the first time by inscribing singleLIRIC layer at 8.3 MHz with a power of 200 mW and a scan speed of 100 mm/s, corresponding to a refractive indexchange of 0.025 after the layer thickness was estimated to be 20 μm. Accordingly, the optimum laser repetition rate usedin femtosecond micromachining corneas can be determined to be around 8.3 MHz, as arbitrary phase structures can bemanufactured by wrapping the phase between 0 and 1 wave.
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