A New Nanosecond UV Laser at 355 nm: Early Results of Corneal Flap Cutting in a Rabbit Model

Trost, Andrea; Strohmaier, Clemens; Bogner, Barbara; Runge, Christian; Kaser-Eichberger, Alexandra; Krefft, Karolina; Vogel, Alfred; Linz, Norbert; Freidank, Sebastian; Zimmermann, Ingfried; Reitsamer, Herbert A.; Reit, Herbert A.

doi:10.1167/iovs.13-12580

Cited by 13 publications

(8 citation statements)

References 40 publications

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“…To date, surgery has mostly been performed at 800 nm and 1040 nm, the wavelengths of Titanium:Sapphire lasers and ytterbium-based lasers [6,8,54]. Recently UV-A pulses have been employed for flap cutting in corneal refractive surgery because the shorter wavelengths provides a better cutting precision due to the shorter plasma length [55][56][57][58]134] Furthermore, the collagen molecules in corneal tissue act as stable centers of reduced excitation energy in UV breakdown that lower the breakdown threshold and minimize mechanical side effects [58]. On the other hand, the wavelengths considerably longer than 1040 nm have been tested for plasma-mediated surgery in strongly scattering tissues such as sclera, skin and brain [59][60][61]63] and in edematous corneas [64].…”

Section: Consequences For Femtosecond Laser Tissue Surgerymentioning

confidence: 99%

Wavelength dependence of femtosecond laser-induced breakdown in water and implications for laser surgery

et al. 2016

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The wavelength dependence of the threshold for femtosecond optical breakdown in water provides information on the interplay of multiphoton, tunneling and avalanche ionization, and is of interest for parameter selection in laser surgery. We measured the bubble threshold from UV to near-IR wavelengths and found a continuous decrease of the irradiance threshold with increasing wavelength λ. Results are compared to the predictions of a numerical model that assumes a bandgap of 9.5 eV and considers the existence of a separate initiation channel via excitation of valence band electrons into a solvated state followed by rapid upconversion into the conduction band. Fits to experimental data yield an electron collision time of ≈ 1 fs, and an estimate for the capacity of the initiation channel. Using that collision time, the breakdown dynamics was explored up to λ = 2 µm. The irradiance threshold first continues to decrease but levels out for wavelengths longer than 1.3 µm. This opens promising perspectives for laser surgery at wavelengths around 1.3 µm and 1.7 µm, which are attractive because of their large penetration depth into scattering tissues.

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Section: Consequences For Femtosecond Laser Tissue Surgerymentioning

confidence: 99%

Wavelength dependence of femtosecond laser-induced breakdown in water and implications for laser surgery

et al. 2016

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“…However, the transition from near-infrared to UV wavelength presents new safety hazards that must be considered before clinical use. Although the 2013 study by Trost et al 4 showed that 6.5-mm diameter corneal flaps could be created in rabbits with no unintended UV-induced damage to the cornea at a total radiant exposure of 6.9 J∕cm 2 , it did not establish an operational range and safety margin for 355-nm lasers. A measurement of the actual damage thresholds is important to establish the safety limits of 355-nm lasers for the full range of flap cutting parameters as well as other potential applications, such as refractive lenticule extraction, 6 lamellar keratoplasty, 7 or cataract surgery.…”

Section: Safety Of Cornea and Iris In Ocular Surgery With 355-nm Lasementioning

confidence: 99%

“…3 Recently, a promising new laser system for corneal flap cutting that uses a subnanosecond microchip ultraviolet (UV) laser has been demonstrated. 4,5 The simpler design of the 355-nm laser offers a much more compact, inexpensive, and precise flap cutter than is possible with current femtosecond lasers. However, the transition from near-infrared to UV wavelength presents new safety hazards that must be considered before clinical use.…”

Section: Safety Of Cornea and Iris In Ocular Surgery With 355-nm Lasementioning

confidence: 99%

“…Photomechanical damage is induced by microexplosions during dielectric breakdownbased laser cutting of the stroma and was shown to be lower with 355-nm nanosecond laser than with 1053-nm wavelength and femtosecond pulse durations. 4,5 Therefore, it is reasonable to assume that laser procedures that are within the photomechanical safety limits for near-infrared femtosecond lasers will not produce additional mechanical damage in 355-nm subnanosecond laser systems. Photothermal damage to ocular tissues may arise from cumulative heating, but that can be mitigated by external cooling of the corneal surface or by reducing the average laser power, albeit at the expense of extended duration of the surgical procedure.…”

Section: Safety Of Cornea and Iris In Ocular Surgery With 355-nm Lasementioning

confidence: 99%

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Safety of cornea and iris in ocular surgery with 355-nm lasers

et al. 2015

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Abstract. A recent study showed that 355-nm nanosecond lasers cut cornea with similar precision to infrared femtosecond lasers. However, use of ultraviolet wavelength requires precise assessment of ocular safety to determine the range of possible ophthalmic applications. In this study, the 355-nm nanosecond laser was evaluated for corneal and iris damage in rabbit, porcine, and human donor eyes as determined by minimum visible lesion (MVL) observation, live/dead staining of the endothelium, and apoptosis assay. Single-pulse damage to the iris was evaluated on porcine eyes using live/dead staining. In live rabbits, the cumulative median effective dose (ED 50 ) for corneal damage was 231 J∕cm 2 , as seen by lesion observation. Appearance of endothelial damage in live/dead staining or apoptosis occurred at higher radiant exposure of 287 J∕cm 2 . On enucleated rabbit and porcine corneas, ED 50 was 87 and 52 J∕cm 2 , respectively, by MVL, and 241 and 160 J∕cm 2 for endothelial damage. In human eyes, ED 50 for MVL was 110 J∕cm 2 and endothelial damage at 453 J∕cm 2 . Single-pulse iris damage occurred at ED 50 of 208 mJ∕cm 2 . These values determine the energy permitted for surgical patterns and can guide development of ophthalmic laser systems. Lower damage threshold in corneas of enucleated eyes versus live rabbits is noted for future safety evaluation. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

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“…For corneal flap cutting, recent studies have introduced a 345-nm femtosecond laser [17][18][19] and 355-nm subnanosecond laser 20 for LASIK and a 1650-nm femtosecond laser for keratoplasty. 21 At the same time, IR femtosecond lasers have been used in the subcavitation regime for refractive index shaping 22,23 and for corneal cross-linking without photosensitizers.…”

Section: Finesse Of Transparent Tissue Cutting By Ultrafast Lasers Atmentioning

confidence: 99%

Finesse of transparent tissue cutting by ultrafast lasers at various wavelengths

2015

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Abstract. Transparent ocular tissues, such as the cornea and crystalline lens, can be ablated or dissected using short-pulse lasers. In refractive and cataract surgeries, the cornea, lens, and lens capsule can be cut by producing dielectric breakdown in the focus of a near-infrared (IR) femtosecond laser, which results in explosive vaporization of the interstitial water, causing mechanical rupture of the surrounding tissue. Here, we compare the texture of edges of lens capsule cut by femtosecond lasers with IR and ultraviolet (UV) wavelengths and explore differences in interactions of these lasers with biological molecules. Scanning electron microscopy indicates that a 400-nm laser is capable of producing very smooth cut edges compared to 800 or 1030 nm at a similar focusing angle. Using gel electrophoresis and liquid chromatography/mass spectrometry, we observe laser-induced nonlinear breakdown of proteins and polypeptides by 400-nm femtosecond pulses above and below the dielectric breakdown threshold. On the other hand, 800-nm femtosecond lasers do not produce significant dissociation even above the threshold of dielectric breakdown. However, despite this additional interaction of UV femtosecond laser with proteins, we determine that efficient cutting requires plasma-mediated bubble formation and that remarkably smooth edges are the result of reduced thresholds and smaller focal volume. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

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A New Nanosecond UV Laser at 355 nm: Early Results of Corneal Flap Cutting in a Rabbit Model

Cited by 13 publications

References 40 publications

Wavelength dependence of femtosecond laser-induced breakdown in water and implications for laser surgery

Wavelength dependence of femtosecond laser-induced breakdown in water and implications for laser surgery

Safety of cornea and iris in ocular surgery with 355-nm lasers

Finesse of transparent tissue cutting by ultrafast lasers at various wavelengths

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