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Adam Boretsky, Joseph Clary, Gary Noojin, Aurora Shingledecker, Benjamin Rockwell; Wavelength Dependence of Infrared Femtosecond Laser Ablation in the Cornea. Invest. Ophthalmol. Vis. Sci. 2018;59(9):1403. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To determine the wavelength dependence of femtosecond laser ablation in explant corneal tissue and corneal tissue phantoms across the near infrared and mid-infrared regions of the electromagnetic spectrum.
A laser system comprised of a high-energy regenerative amplifier and optical parametric amplifier outputting ~100 femtosecond pulses with pulse energies up to 2 mJ was used to determine damage/ablation thresholds at 100 nm increments between 1.2 - 3.0 μm in explant porcine corneas and transparent collagen gel tissue phantoms. Damage was characterized using spectral domain optical coherence tomography (SD-OCT) to identify multiple features of laser ablation including surface area, depth, and volume as a function of pulse energy, wavelength, and pulse repetition.
The ablation threshold values varied from 0.1 – 2.0 J/cm2 across the wavelength range studied. For each wavelength, the presence or absence of ablation was consistent across multiple exposures (n=10 repetitions per condition), indicating a deterministic damage threshold. The ablation surface area and volume were highly dependent on the pulse energy, pulse repetition, and wavelength. The ablation surface area began to plateau at approximately 1-5 J/cm2 and the ablation depth decreased at longer wavelengths, which exhibit greater water absorption.
The determination of damage thresholds for ultrashort-pulsed lasers in sensitive ocular tissue, such as the cornea, is an important step to provide guidance and establishment of appropriate MPE levels for safety standards. The identification of ablation thresholds in this regime may also provide new opportunities for precision surgery in ocular tissue using these spectral and pulse-width regions. Additionally, the identification of ablation thresholds across a wide range of wavelengths will provide a better understanding of the fundamental mechanisms of ultrafast laser-tissue interactions in the mid-infrared region of the spectrum.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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