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Nima Khatibzadeh, Alireza Malek Tabrizi, James E Hill, Saidur Rahaman, Zenon Witowski, Zheng Sun, Saeed Taheri, Hong Fu; Laser Tissue Evaluation for a Novel Ultrashort Femtosecond Laser with Auto-Z Calibration. Invest. Ophthalmol. Vis. Sci. 2017;58(8):5292.
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© ARVO (1962-2015); The Authors (2016-present)
Femtosecond laser has been used for creating LASIK flap, inlay channel, and other corneal incisions. To further advance the femtosecond technology, we evaluated a novel ultrashort femtosecond laser. The purpose here is to present the experimental results for flap and inlay channel incisions.
The novel ultrashort femtosecond laser was built with an ultrashort fiber laser, a high numerical aperture beam delivery, and an ultrafast scanning. The cutting depth is controlled with sub-micron precision using an innovative automatic glass interface detection device (Auto-Z). Over 200 ex-vivo pig eyes were used in the evaluation.
1-Flap thickness consistency: 9mm diameter flap with a targeted thickness of 80μm was performed on 50 pig eyes, with side cut energy=110nJ/pulse, bed cut energy=70nJ/pulse, and the cutting time was 8.7s. All flaps showed tissue-bridge free dissection and easy lift as evaluated by subject matter experts (SME). The achieved average thickness=81µm, the standard deviation=1.9µm comparing to 5–12µm for on-market products.2-Flap cutting time: by increasing bed cut energy to 90nJ/pulse and accelerating scanning speed, 5.0 s cutting time was achieved. Tissue roughness of the flap was measured using a white light interferometer: mean roughness=1.6±0.7µm, RMS roughness=2.0±0.9µm (N=8), comparing to mean=2.6µm and RMS=3.2µm of a control flap cut with iFS Advanced Femtosecond Laser.3-Flap bubble releasing: to ensure there is always a gas escape channel, the flap incision starts with the side cut, then a ring bed cut underneath the side cut, then the bed cut. Random gas bursts from the side cut was observed in flap incisions; no gas buildup inside the flap was observed (N=10).4-Inlay channel: both standard and lollipop inlay channel patterns on pig eyes demonstrated uniform bubble patterns and ease of insertion for the Inlay disk with no significant adhesion judged by SME. Placement depth of the Inlay disk measured by an OCT was ±6µm of the intended depth of 200µm (N=10).
We have shown with preliminary pig eye results that the novel ultrashort femtosecond laser can create tissue-bridge free flap incisions and Inlay channels with superior thickness consistency, smooth tissue dissection, no gas buildup, and shortened cutting time. We plan to perform further experiments on cadaver eyes.
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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