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Vilnius, Lithuania

Gabryte E.,Light Conversion Ltd | Danielius R.,Light Conversion Ltd | Ruksenas O.,Vilnius University
Journal of Cataract and Refractive Surgery

Purpose: To determine the effectiveness of femtosecond ultraviolet (UV) pulses in ablating corneal stroma in a rabbit model and to compare the healing response between eyes treated with femtosecond UV pulses and eyes treated with standard excimer photorefractive keratectomy. Setting: Laser Research Center, Vilnius University, Vilnius, Lithuania. Design: Experimental study. Methods: Myopic photoablation using a femtosecond UV solid-state laser system was applied to corneas of pigmented rabbits. Experiments in 16 eyes were performed for optimization of the laser system parameters (fluence, spot size, pulse repetition rate) and calibration of ablation rate. In 7 rabbits, deep femtosecond UV ablation (∼130 μm) in 1 eye and shallow ablation (∼30 μm) in the contralateral eye were performed. Nine rabbits received an approximately 30 μm ablation with femtosecond UV pulses in 1 eye and with a conventional excimer system in the contralateral eye. Two eyes were used as controls. The ablation process and surface-temperature dynamics were monitored and recorded. Surface quality and haze development were evaluated. Rabbits were humanely killed 0 to 6 months after surgery, and eyes were enucleated for histological examination. Results: Rabbit corneas ablated with femtosecond UV pulses or excimer laser radiation were similar in terms of the corneal wound-healing process, surface quality, and histology. Conclusions: The experiments indicate the feasibility of clinical application of femtosecond UV lasers for stromal ablation. The ability to switch between laser harmonics allows fast changeover from infrared to the UV mode, implying that a wide range of ophthalmic procedures can be performed using a single solid-state laser device. Financial Disclosure: Ms. Gabryte and Mr. Danielius are paid employees of Light Conversion Ltd. Mr. Danielius is a shareholder of Light Conversion Ltd. No other author has a financial or proprietary interest in any material or method mentioned. © 2012 ASCRS and ESCRS. Source

Morkunas V.,Vilnius University | Ruksenas O.,Vilnius University | Vengris M.,Vilnius University | Gabryte E.,Vilnius University | And 3 more authors.
Photomedicine and Laser Surgery

Background Data: Research on the damaging effect of ultraviolet (UV) laser irradiation on the DNA of live organisms is still scarce, although UV lasers are increasingly being used in therapeutics and surgical treatment. Objective: In this study we investigated the effect of new-generation 205-nm femtosecond solid-state laser irradiation on the DNA of murine bone marrow cells in vitro. Materials and Methods: Mouse bone marrow cells in distinct plates were exposed to different doses of 205-nm femtosecond laser irradiation. Single-cell gel electrophoresis, or comet, assay was used for DNA damage measurement. Results: Our study revealed intensity-dependent genotoxic, genotoxic-cytotoxic, or cytotoxic impact of laser irradiation. The lowest doses we used (0.0175-0.105J/cm 2) induced DNA photodamage in irradiated cells directly, medial doses (0.175 and 0.35J/cm 2) caused both direct damage of genetic material and irreversible injury of cell's structure whereas the highest doses (1.05-4.2J/cm 2) caused the death of most irradiated cells. It is worrisome that even comparatively low doses of irradiation were genotoxic. Exposure to the lowest-intensity irradiation (0.0175J/cm 2) caused a highly significant (p<0.0001) increase in DNA strand breaks of bone marrow cells: the mean ± SEM %DNA score in the comet tail was 9.96 ± 0.56 compared with 3.58 ± 0.80 for controls. Investigation of the effects of low and medial intensities of irradiation showed a dosage-effect relationship of R 2=0.84, P<0.01. Conclusion: New-generation 205-nm femtosecond laser irradiation produced a genotoxic effect by inducing strand breaks in the DNA of murine bone marrow cells in vitro. Research on the possible genotoxic effects of this laser on corneal and skin epithelial cells in vivo is needed. © Copyright 2011, Mary Ann Liebert, Inc. 2011. Source

Morkunas V.,Vilnius University | Gabryte E.,Light Conversion Ltd | Gabryte E.,Vilnius University | Vengris M.,Vilnius University | And 3 more authors.
Photomedicine and Laser Surgery

Objective: The purpose of this study was to investigate the possible genotoxic impact of new generation 205 nm femtosecond solid-state laser irradiation on the DNA of murine bone marrow cells in vitro, and to compare the DNA damage caused by both femtosecond and nanosecond UV laser pulses. Background data: Recent experiments of corneal stromal ablation in vitro and in vivo applying femtosecond UV pulses showed results comparable with or superior to those obtained using nanosecond UV lasers. However, the possible genotoxic effect of ultrashort laser pulses was not investigated. Methods: Mouse bone marrow cells were exposed to different doses of 205 nm femtosecond, 213 and 266 nm nanosecond lasers, and 254 nm UV lamp irradiation. The comet assay was used for the evaluation of DNA damage. Results: All types of irradiation demonstrated intensity-dependent genotoxic impact. The DNA damage induced depended mainly upon wavelength rather than on other parameters such as pulse duration, repetition rate, or beam delivery to a target. Conclusions: Both 205 nm femtosecond and clinically applied 213 nm nanosecond lasers' pulses induced a comparable amount of DNA breakage in cells exposed to the same irradiation dose. To further evaluate the suitability of femtosecond UV laser sources for microsurgery, a separate investigation of the genotoxic and mutagenic effects on corneal cells in vitro and, particularly, in vivo is needed. © Copyright 2015, Mary Ann Liebert, Inc. 2015. Source

Budriunas R.,Vilnius University | Stanislauskas T.,Vilnius University | Stanislauskas T.,Light Conversion Ltd | Varanavicius A.,Vilnius University
Journal of Optics (United Kingdom)

We report the recent results on development of a CEP-stable 1 kHz repetition rate TW-class OPCPA system driven by femtosecond Yb:KGW and picosecond Nd:YAG pump sources. Seed pulses with spectra spanning over an octave are produced in a continuum generator pumped by CEP-stable pulses from a difference frequency generator operated at 1.3-1.6 μm. After amplification in NOPA, pulses with energy up to 70 μJ and spectra supporting durations of 5 fs are obtained. Sub-70 mrad CEP jitter at the output of system frontend is demonstrated. © 2015 IOP Publishing Ltd. Source

Stanislauskas T.,Vilnius University | Budriunas R.,Vilnius University | Antipenkov R.,Vilnius University | Zaukevicius A.,Ekspla Ltd. | And 9 more authors.
Optics Express

We present a compact TW-class OPCPA system operating at 800 nm. Broadband seed pulses are generated and pre-amplified to 25 mJ in a white light continuum seeded femtosecond NOPA. Amplification of the seed pulses to 35 mJ at a repetition rate of 10 Hz and compression to 9 fs is demonstrated. © 2014 Optical Society of America. Source

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