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Alireza Malek Tabrizi, James E Hill, Nima Khatibzadeh, Saeed Taheri, Hong Fu; A Novel Ultrashort Femtosecond Laser with Ultrafast Scanner for Corneal Lenticule Surgery. Invest. Ophthalmol. Vis. Sci. 2017;58(8):5289. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Corneal lenticular incision procedure has recently become an alternative refractive vision correction procedure. To improve the precision of lenticular geometry by minimizing residual tissue bridge in the lenticule dissection, improving centration, and reducing suction break rate, we evaluated a novel ultrashort femtosecond laser with shorter pulsewidth, tighter focus, high pulse reprate, and ultrafast scanning. The purpose of this poster is to describe the ultrafast scanning mechanism and present preliminary lenticule incision results on ex-vivo pig eyes.
The ultrafast scanning mechanism is capable to: a) Scan a 10 MHz laser pulse train into a densely packed cutting pattern of about 1μm x1μm spot separation, which is the key to minimize residual tissue bridges. b) Cut curved lenticular surfaces with submicron thickness control in the cutting trajectory, which is the key to improve refractive correction accuracy. c) Cut angled entry cuts. d) Reserve laser beam quality to achieve diffraction-limited focus spot during ultrafast scanning. This scanning mechanism consists of 6 synchronized motors: an ultrafast 8 kHz resonant scanner, a scan line rotator, a slow-z motor, a fast-z motor, X and Y linear motors.
a) To confirm the trajectory thickness control precision, lenticular incision was performed on 8 glass samples: the target and achieved center thicknesses were within the measurement error of ±1μm.b) The lenticule incisions using 70nJ pulse energy and 28s cutting were performed on 50 pig eyes: the lenticule can be removed easily without the need to separate the two cutting surfaces prior to the removal.c) An optimized algorithm with reduced pulse overlap showed with 5 pig eyes that the lenticular incision with the same easiness of lenticule removal can be done within 15s without degradation of thickness or bed depth consistency.d) It is shown with 5 pig eyes that the pulse energy can be as low as 40nJ to dissect tissue-bridge free lenticule without degradation of thickness or bed depth consistency.
We have shown that the novel ultrashort femtosecond laser technology with ultrafast scanning is capable to perform tissue-bridge free lenticule incisions at 70nJ pulse energy and within 15s. This technology has the potential to perform wavefront guided lenticule incision with iris registration. We plan to evaluate this technology for cadaver eyes in the near future.
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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