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ZENON WITOWSKI, Saidur Rahaman, Zheng Sun, Alireza Malek Tabrizi, James E Hill, Hong Fu; Novel Ultrashort Femtosecond Laser Characterization. Invest. Ophthalmol. Vis. Sci. 2017;58(8):5293.
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© ARVO (1962-2015); The Authors (2016-present)
Femtosecond lasers have been used for LASIK flap creation, lenticule incision, and other corneal surgeries. The cutting mechanism is provided by the plasma-induced micro-cavitation bubble. The fundamental limit for cutting precision and cutting quality is determined by two critical parameters: the laser pulsewidth and the focus spot size. Shorter pulsewidth and smaller focus spot will result in more precise dissection and less collateral tissue disturbance. The purpose of this poster is to present characterization results for a novel ultrashort femtosecond laser that uses a very short pulsewidth and smallest spot size.
Experimental setup was built with a femtosecond fiber laser, a high numerical-aperture beam delivery, and an ultrafast scanning module. To achieve the shortest pulsewidth at the cut point, the laser is pre-compensated for the pulse broadening introduced by the group-velocity dispersion of the beam delivery optics. The effect of pulsewidth on tissue dissection was evaluated based on incisions on pig eyes. The laser pulsewidth at the focus was characterized with a Frequency-Resolved-Optical-Gate instrument. The focus spot size in water was measured with a customized water immersed spot size camera.
a) The effect of pulsewidth on tissue dissections on pig eyes was evaluated with 2 different types of fiber lasers and 1 free-space laser, and for a given fiber laser with different pulsewidth settings. It was observed that that there is a small but definitive difference in both flap creation and lenticule incision: a laser with 100-200fs pulsewidth produces easier flap lift and lenticule removal than that with pulsewidth ≥250fs.b) The pulsewidth at the focus of 8 femtosecond fiber lasers were measured: they are all within the target range of 100 fs to 200 fs, confirming the effectiveness of the pre-compensation mechanism.c) The focus spot sizes in the surgical volume for 5 such setups were measured: the 50%-energy spot diameters are all well below 1.3μm, achieving the design target for the diffraction-limited beam delivery optics.
We have characterized a novel ultrashort femtosecond laser that uses a shorter pulsewidth and smallest focus spot size compared with ophthalmic femtosecond lasers on the market. The preliminary cutting results show that this novel technology has the potential to produce more precise and tissue-bridge free corneal incisions.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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