WorldWideScience

Sample records for excimer laser keratomileusis

  1. Multifocal Corneal Excimer Femtosecond Laser in situ Keratomileusis following Radial Keratotomy: A Case Report with Six Months of Follow-Up

    Directory of Open Access Journals (Sweden)

    Iraklis Vastardis

    2014-12-01

    Full Text Available We report the case of a 46-year-old female patient who was referred to our clinic (Orasis Eye Clinic, Reinach, Switzerland seeking improvement of her distance and near visual acuity. Radial keratotomy (RK was performed at a younger age on both eyes to correct -5 D myopia. The patient underwent a bilateral same-session multifocal corneal excimer femtosecond laser (Supracor keratomileusis correction. We introduce a new correction approach, possibly suitable for presbyopic patients previously treated with RK, and we present several potential novel advantages such as enhanced near, intermediate vision, and improvement in quality of life. This is the first report of a bilateral excimer laser treatment attempt of presbyopia following RK.

  2. Long-term efficacy of excimer laser in situ keratomileusis in the management of children with high anisometropic amblyopia.

    Science.gov (United States)

    Lin, Xiao-Ming; Yan, Xiao-He; Wang, Zheng; Yang, Bin; Chen, Qi-Wen; Su, Jin-Ai; Ye, Xue-Lian

    2009-04-05

    Children with anisometropic amblyopia are often noncompliant with traditional treatment including spectacules and contact lenses. This study was to evaluate the long-term efficacy of excimer laser in situ keratomileusis (LASIK) for children with high anisometropic amblyopia. A retrospective analysis of 24 children with high unilateral anisometropic amblyopia, who underwent LASIK during the period between August 2000 and September 2005 in our hospital, was conducted. The mean age of these children was (7.4 +/- 1.9) years (range 5 - 14 years) and the mean follow-up period was (33.3 +/- 14.2) months (range 18.5 - 74.2 months). After LASIK, visual acuity, refraction and far or near stereoacuity were analyzed. Near stereoacuity was measured by the random-dot butterfly stereogram and the pre-school random-dot stereogram, while far stereoacuity was measured by the synoptophore with Yan's random-dot stereogram. Mean preoperative uncorrected visual acuity was 0.06 +/- 0.05, while mean postoperative uncorrected visual acuity was elevated to 0.43 +/- 0.33. Mean preoperative best-corrected visual acuity was 0.26 +/- 0.22, while mean postoperative best-corrected visual acuity was elevated to 0.67 +/- 0.40. For patients with myopic anisometropia, preoperative mean spherical equivalent refraction was (-8.01 +/- 2.70) D while postoperative value significantly reduced to (-1.32 +/- 2.47) D. For patients with hyperopic anisometropia, preoperative mean spherical equivalent refraction was (+7.35 +/- 1.55) D while postoperative value significantly reduced to (+3.30 +/- 0.86) D. These results demonstrated that there was statistical difference in these parameters between preoperative and postoperative tests. At the last follow-up, 20 patients had near stereoacuity, and the mean near stereoacuities measured by the random-dot butterfly stereogram and the preschool random-dot stereogram were (149.00 +/- 152.93)'' and (201.05 +/- 235.94)'', respectively. In contrast, 11 patients had far

  3. excimer laser

    Indian Academy of Sciences (India)

    2014-01-07

    Jan 7, 2014 ... Excimer laser; krypton chloride; UV pre-ionization; gas circulation. PACS No 42.55.Lt. 1. ... active discharge volume is by spark UV radiation created adjacent to both sides of the. Figure 4. Output ... HV electrode, all along its length and spatially modulated to ensure uniform irradiation of the gas volume.

  4. Biomechanical and wound healing characteristics of corneas after excimer laser keratorefractive surgery: is there a difference between advanced surface ablation and sub-Bowman's keratomileusis?

    Science.gov (United States)

    Dawson, Daniel G; Grossniklaus, Hans E; McCarey, Bernard E; Edelhauser, Henry F

    2008-01-01

    To describe the biomechanical and wound healing characteristics of corneas after excimer laser keratorefractive surgery. Histologic, ultrastructural, and cohesive tensile strength evaluations were performed on 25 normal human corneal specimens, 206 uncomplicated LASIK specimens, 17 uncomplicated sub-Bowman's keratomileusis (SBK) specimens, 4 uncomplicated photorefractive keratectomy (PRK) specimens, 2 uncomplicated advanced surface ablation (ASA) specimens, 5 keratoconus specimens, 12 postoperative LASIK ectasia specimens, and 1 postoperative PRK ectasia specimen and compared to previously published studies. Histologic and ultrastructural studies of normal corneas showed significant differences in the direction of collagen fibrils and/or the degree of lamellar interweaving in Bowman's layer, the anterior third of the corneal stroma, the posterior two-thirds of the corneal stroma, and Descemet's membrane. Cohesive tensile strength testing directly supported these morphologic findings as the stronger, more rigid regions of the cornea were located anteriorly and peripherally. This suggests that PRK and ASA, and secondarily SBK, should be biomechanically safer than conventional LASIK with regard to risk for causing keratectasia after surgery. Because adult human corneal stromal wounds heal slowly and incompletely, all excimer laser keratorefractive surgical techniques still have some distinct disadvantages due to inadequate reparative wound healing. Despite reducing some of the risk for corneal haze compared to conventional PRK, ASA cases still can develop corneal haze or breakthrough haze from the hypercellular fibrotic stromal scarring. In contrast, similar to conventional LASIK, SBK still has the short- and long-term potential for interface wound complications from the hypocellular primitive stromal scar. Ophthalmic pathology and basic science research show that SBK and ASA are improvements in excimer laser keratorefractive surgery compared to conventional LASIK or

  5. Laser in situ keratomileusis with a scanning excimer laser for the correction of low to moderate myopia with and without astigmatism.

    Science.gov (United States)

    Balazsi, G; Mullie, M; Lasswell, L; Lee, P A; Duh, Y J

    2001-12-01

    To evaluate the safety and effectiveness of and patient satisfaction with laser in situ keratomileusis (LASIK) performed with a scanning excimer laser by experienced surgeons to correct low and moderate levels of myopia and astigmatism. Clinique Laservue, Montreal, Quebec, Canada. A consecutive series of 125 patients (236 eyes) with myopia of -0.5 to -7.0 diopters (D) and cylinder less than 2.5 D were enrolled in this single-center prospective clinical trial. The patients were treated with LASIK and followed for 6 months. The System-ALK Automated Corneal Shaper microkeratome (Bausch & Lomb Surgical) with a 180 microm thickness plate and the Technolas 217 excimer laser (Bausch & Lomb Surgical) with PlanoScan software for the stromal ablation were used in all procedures. Since this version of PlanoScan tended to undercorrect, a mean of 14.7% was added to the standard nomogram. Patient satisfaction was assessed by questionnaires administered preoperatively and 1 and 6 months postoperatively. Retreatments for enhancement were not performed during the 6-month follow-up. Six months after LASIK (86.4% follow-up), the mean postoperative manifest spherical equivalent was +0.02 D +/- 0.64 (SD) compared with a preoperative mean of -4.01 +/- 1.59 D. The uncorrected visual acuity was 20/40 or better in 94.6% of eyes and 20/20 or better in 81.9%. A total of 91.2% were within +/-1.0 D of emmetropia and 73.0% were within +/-0.5 D. Only 2 eyes were overcorrected by >1.0 D. Of the eyes with astigmatic myopia, 86.8% were within +/-1.0 D of the intended cylinder correction (by vector analysis) and 73.0% were within +/-0.5 D. The refractions were generally stable after 1 month, and the change in refraction between postoperative examinations was within +/-0.5 D in 88.0% of eyes. A 1-line decrease in best spectacle-corrected visual acuity was seen in 11.3% of eyes, and no eye lost more than 1 line. An increase of 1 or 2 lines was seen in 45.1%. No intraoperative problems occurred, and

  6. Excimer Laser Technology

    CERN Document Server

    Basting, Dirk

    2005-01-01

    This comprehensive survey on Excimer Lasers investigates the current range of the technology, applications and devices of this commonly used laser source, as well as the future of new technologies, such as F2 laser technology. Additional chapters on optics, devices and laser systems complete this compact handbook. A must read for laser technology students, process application researchers, engineers or anyone interested in excimer laser technology. An effective and understandable introduction to the current and future status of excimer laser technology.

  7. Excimer Laser Etching

    Energy Technology Data Exchange (ETDEWEB)

    Boatner, Lynn A [ORNL; Longmire, Hu Foster [ORNL; Rouleau, Christopher M [ORNL; Gray, Allison S [ORNL

    2008-04-01

    Excimer laser radiation at a wavelength of = 248 nm represents a new etching method for the preparation of metallographic specimens. The method is shown to be particularly effective for enhancing the contrast between different phases in a multiphase metallographic specimen.

  8. Thin-flap laser-assisted in situ keratomileusis.

    Science.gov (United States)

    Slade, Steven G

    2008-07-01

    Concerns regarding the increasing incidence of corneal ectasia following laser in situ keratomileusis procedures, together with increased understanding of the biomechanics of the cornea, has resulted in many refractive surgeons returning to surface ablation techniques such as photorefractive keratectomy. Even if surface ablation techniques offer a higher degree of safety than LASIK, they are associated with more pain and a slower visual recovery in the immediate postoperative period. This highlights the need for alternative procedures that offer the combined advantages of laser in situ keratomileusis and photorefractive keratectomy. Sub-Bowman's keratomileusis is a new procedure that provides the biomechanical stability and associated safety of photorefractive keratectomy with the visual results and reduced pain experience of laser in situ keratomileusis. This technique involves the use of the femtosecond laser to create a customized corneal flap of between 90 and 110 mum with a diameter based on the requirements of the individual patient and the type of excimer laser being used. This review outlines the rationale for sub-Bowman's keratomileusis and describes the efficacy, tolerability and safety of the procedure compared with photorefractive keratectomy.

  9. Excimer lasers for refractive surgery

    Science.gov (United States)

    Vartapetov, Serge K.

    2003-10-01

    Over the last decade excimer lasers have been broadly used for technological and medical processes. One of the most widespread applications of excimer laser is the clinical use for refractive surgery. Refractive surgery with excimer lasers is the prevalent method for the eye acuity correction. Operation at 193 nanometers, the excimer laser is able to precisely sculpt the corneal surface to correct refractive errors. Both the increase in the accuracy of sculpturing and the predictability of procedures are the key elements of the excimer laser designed for refractive surgery. The novel excimer laser for refractive surgery is offered for small aberration treatment. The excimer laser with both a full aperture Gaussian beam and fly spot system is described. The comparison of different systems of laser correction is reviewed.

  10. O impacto da cirurgia de ceratectomia fotorrefrativa (PRK e ceratomileuse assistida por excimer laser in situ (LASIK na qualidade visual e de vida em pacientes com ametropias The impact of photorefractive excimer laser keratectomy (PRK and laser in situ keratomileusis (LASIK on visual quality and life in patients with ametropias

    Directory of Open Access Journals (Sweden)

    Ricardo Belfort

    2008-02-01

    significantemente para melhor em relação ao préoperatório, com redução substancial do estresse psicológico.PURPOSE: To evaluate the quality of life, vision and stress before and after refractive surgery. METHODS: This is a longitudinal, observational study, where 100 patients were evaluated; 54 espectacles wearers, 21 contact lens users before surgery and 25 controls wearers spectacles or contact lenses, who did not want to undergo refractive surgery during one year despite refractive error. The applied questionnaires were Self Reporting Questionnaires SRQ-20 of quality of life and vision and National Eye Institute Visual Function Questionnaire NEI VFQ-25 for the assessment of mental health. The intervention group answered the questionnaires before surgery, three, six and twelve months after follow-up and the control group answered the questionnaires at six and twelve months after the baseline. The questionnaires of the intervention group were applied by an independent person. RESULTS: In the intervention group (54 spectacle wearers, 39 were treated by photorefractive excimer laserkeratectomy (PRK and 15 by laser in situ keratomileusis (LASIK, of the 21 contact lens users: 12 received photorefractive excimer laser keratectomy and nine were treated by laser in situ keratomileusis (LASIK. The control group remained stable during the study. After three months of follow-up the intervention group showed improvement in quality of life, vision and reduction of stress. After one year of follow-up the assessments of quality of life and mental health were similar to the control group. After three months there was a significant reduction of psychiatric symptomatology in the intervention group. CONCLUSION: Patients operated for correction of ametropia showed a significant improvement in quality of life and mental health assessments.

  11. Ectasia after laser in situ keratomileusis.

    Science.gov (United States)

    Rabinowitz, Yaron S

    2006-10-01

    The potential for litigation has resulted in increased interest in ectasia after laser in situ keratomileusis. This article summarizes papers written during this past year on this subject. A panel of refractive surgery experts have summarized the current state of knowledge on this subject and provided guidelines to minimize risk. Because ectasia may occur in the absence of risk factors, there may be corneas with biomechanical factors not detectable with present technology which are at risk. Several articles point out the limitations of the Orbscan (Bausch & Lomb, Rochester, New York, USA), in particular its accuracy and reproducibility with regard to data generated from the posterior surface of the cornea. A biomechanical model of the cornea is proposed which suggests that each cornea's response to laser in situ keratomileusis is unique. Several case reports are also reviewed which provide insight into pathogenesis and potential new treatment options; these include reports on histopathology, topographic pseudokeratectasia, ectasia from transient raised intraocular pressure, poor response to laser in situ keratomileusis after incisional surgery, intracorneal rings, collagen cross-linking and conductive keratoplasty to stabilize and sphericize the cornea with ectasia. Our knowledge about ectasia is still in evolution. Insights into the biomechanics and genetics of the cornea may allow us to further reduce its occurrence.

  12. Laser in situ keratomileusis in myopic patients with congenital nystagmus.

    Science.gov (United States)

    Mahler, Ori; Hirsh, Ami; Kremer, Israel; Barequet, Irina S; Marcovich, Arie L; Nemet, Pinhas; Levinger, Samuel

    2006-03-01

    To evaluate the results of laser in situ keratomileusis (LASIK) and IntraLASIK in the treatment of myopic patients with nystagmus. Eight patients with congenital nystagmus (16 eyes), aged 23 to 49 years, had LASIK surgery. Corneal flaps were created using the Bausch & Lomb Hansatome microkeratome or the IntraLase femtosecond laser. The ablations were performed with the Bausch & Lomb excimer laser with an active tracking system. In some patients, the eyes were fixated with forceps or a fixation ring during laser ablation. The refractive errors were corrected in all cases. There was no decentration or loss of best corrected visual acuity greater than 1 line. In 56% of the eyes, the postoperative uncorrected visual acuity was better than the best spectacle-corrected visual acuity (BSCVA). The BSCVA improved in 62.5% of the eyes. The overall visual performance improved in all patients. One patient who did not drive before surgery became eligible for a driver's license after surgery. Selected patients with myopia and congenital nystagmus may benefit from laser refractive surgery. Laser refractive surgery may be safely and accurately performed using the Hansatome microkeratome or the IntraLase femtosecond laser and an active tracking system with or without mechanical fixation. The BSCVA may improve in certain patients postoperatively.

  13. Excimer laser drilling of polymers

    Science.gov (United States)

    Chen, Yihong; Zheng, HongYu; Wong, Terence K. S.; Tam, Siu Chung

    1997-08-01

    Laser micro-drilling technology plays a more and more important role in industry, especially in the fabrication of multi-layer electronic packages. In such applications, non- metals are often used as insulators, in which via holes are formed to provide vertical interconnections for densely packed 3D wiring networks. Mechanical punch tools have been the primary means to form holes in ceramic sheets and in polymer boards since the 1970's. As the cost of fabricating punch heads increases drastically and the demand for quick turn around part build becomes more routine, flexible via forming technologies, such as laser drilling, have become more prevalent. In laser drilling, CO2, Nd:YAG, and excimer lasers are often used. Their drilling capabilities, drilling mechanisms, and hole qualities are different because of the different laser beam characteristics such as wavelength and beam energy distribution. In this paper, the mechanisms of laser drilling are briefly reviewed. The results of the experiments on excimer laser drilling of two types of polymer: polyimide and polyethylene terephthalate, are reported. It is found that the etch rate increases with increase of fluence, an the wall angle of drilled holes is dependent on the fluence. The material removal by a laser pulse is highly controllable. There exists an optimal fluence range to obtain clean and smooth edges of quality holes for a given material at a given laser wavelength.

  14. Corneal wound healing after excimer laser keratectomy.

    Science.gov (United States)

    Kaji, Yuichi; Yamashita, Hidetoshi; Oshika, Tetsuro

    2003-03-01

    Excimer laser keratectomy is widely used to correct refractive errors. Several complications of excimer laser keratectomy are reported including corneal infection, regression, corneal haze formation, glare and halo. Most of the complications are closely related to the corneal stromal wound healing process. In order to perform the excimer laser keratectomy with minimum complications, we should understand the mechanism of the corneal stroma wound healing process. In addition, such knowledge will help us to regulate the corneal stromal wound healing process in the future. In the present article, we discuss the molecular mechanism of the corneal stromal wound healing process after excimer laser keratectomy and its regulation by anti-inflammatory agents.

  15. (308 nm) excimer laser

    Indian Academy of Sciences (India)

    The UV lasers with high quantum energy photons directly break the atomic and molecular bonds within material. The photons in this spectral range are also capable of inducing photo- chemical reactions. Most solid materials have high absorption in the UV. The short pulses result in reducing interaction time between laser ...

  16. Excimer laser etching of polyimide

    Science.gov (United States)

    Brannon, J. H.; Lankard, J. R.; Baise, A. I.; Burns, F.; Kaufman, J.

    1985-09-01

    It is reported that thin films of polyimide are efficiently etched in air at pulsed excimer laser wavelengths of 248, 308, and 351 nm. Etch rate versus incident fluence data are found to obey a Beer-Lambert etching relation. Sharp laser fluence thresholds for significant etching are found to correlate with the wavelength-dependent absorption coefficient. The absorbed energy density required to initiate significant etching is found, within experimental error, to be independent of the wavelengths examined. It is felt that this information demonstrates the predominantly thermal nature of the laser etching mechanism. Additionally, infrared spectroscopy and coupled gas chromatography/mass spectroscopy were used to identify several gases evolved during pulsed laser etching of polyimide in both air and vacuum.

  17. Applications of the Excimer Laser: A Review.

    Science.gov (United States)

    Beggs, Sarah; Short, Jack; Rengifo-Pardo, Monica; Ehrlich, Alison

    2015-11-01

    The 308-nm excimer laser has been approved by the Food and Drug Administration for the treatment of psoriasis and vitiligo. Its ability to treat localized areas has led to many studies determining its potential in the treatment of focal diseases with inflammation or hypopigmentation. To review the different applications of the 308-nm excimer laser for treating dermatologic conditions. An extensive literature review was conducted by searching PubMed, MEDLINE, and ClinicalKey to find articles pertaining to dermatologic conditions treated with the 308-nm excimer laser. Articles published that contributed to new applications of the excimer laser were included, as well as initial studies utilizing the excimer laser. The outcomes and results were compiled for different dermatologic conditions treated with the excimer laser. The 308-nm excimer laser has a wide range of uses for focal inflammatory and hypopigmented conditions. Treatment is generally well tolerated, with few adverse reactions. Larger studies and studies evaluating the long-term effects of the 308-nm excimer laser are needed.

  18. Mitomicina C e "Excimer laser" Mitomycin C and Excimer Laser

    Directory of Open Access Journals (Sweden)

    Anelise Dutra Wallau

    2005-12-01

    Full Text Available A mitomicina C é um antimetabólito que atua em nível celular bloqueando a replicação de DNA e RNA e inibindo a síntese protéica. Utilizada em diversas áreas da oftalmologia, recentemente vem sendo empregada como moduladora da resposta cicatricial corneana em cirurgias ópticas/refrativas por "excimer laser". A aplicação única de mitomicina C associada à cirurgia fotoablativa de superfície corneana tem se mostrado opção segura e eficiente para fins terapêuticos em olhos com opacidade corneana pré-existente e/ou profiláticos em olhos com alto risco de desenvolvimento de opacificação corneana pós-operatória. O uso da droga em cirurgia fotoablativa deve ser cauteloso até que seguimento de longo prazo avalie sua inocuidade tardia. O presente texto faz revisão dos principais estudos sobre modulação da resposta cicatricial corneana com uso de mitomicina C em cirurgias ópticas/refrativas de superfície.Mitomycin C is an antimetabolite agent that blocks DNA and RNA replication and protein synthesis. It has been used in several ophthalmologic areas, and recently as a modulator of corneal wound healing in excimer laser surgeries. A single application of mitomycin C during surface corneal photoablative surgery seems a safe and efficient therapeutic option for eyes with corneal opacity and/or as prophylaxis in eyes with high risk for corneal opacity development. The use of this drug in photoablative surgery should be cautious until long-term safety results have been reported. The present text presents a review about corneal wound healing with the use of mitomycin C.

  19. 308-nm excimer laser in endodontics

    Science.gov (United States)

    Liesenhoff, Tim

    1992-06-01

    Root canal preparation was performed on 20 extracted human teeth. After opening the coronal pulp, the root canals were prepared by 308 nm excimer laser only. All root canals were investigated under SEM after separation in the axial direction. By sagittal separation of the mandibles of freshly slaughtered cows, it was possible to get access to the tissues and irradiate under optical control. Under irradiation of excimer laser light, tissue starts to fluoresce. It was possible to demonstrate that each tissue (dentin, enamel, bone, pulpal, and connective tissue) has a characteristic spectral pattern. The SEM analyses showed that it is well possible to prepare root canals safely. All organic soft tissue has been removed by excimer laser irradiation. There was no case of via falsa. The simultaneous spectroscopic identification of the irradiated tissue provides a safe protection from overinstrumentation. First clinical trials on 20 patients suffering of chronical apical parodontitis have been carried out successfully.

  20. Curative effects of excimer laser corneal refractive surgery for hyperopic anisometropic amblyopia

    Directory of Open Access Journals (Sweden)

    Xin-Gang Nie

    2017-07-01

    Full Text Available AIM: To investigate curative effects of excimer laser corneal refractive surgery for adults or older adolescent with hyperopic anisometropic amblyopia. METHODS: From March 2014 to March 2016, we selected 26 cases 26 eyes of adults or older adolescent with hyperopic anisometropic amblyopia in our hospital. All eyes underwent laser in situ keratomileusis, observed for the uncorrected visual acuity(UCVA, best corrected visual acuity(BCVA, diopter and stereopsis. RESULTS: At the end of the follow-up, the patient's spherical equivalent and anisometropia were 1.47±0.51D and 1.15±0.22D, were significantly lower than that before operation(PPPCONCLUSION: In adult or older adolescent with hyperopic anisometropic amblyopia, excimer laser corneal refractive surgery has a certain effect.

  1. Hyperopic laser in situ keratomileusis: comparison of femtosecond laser and mechanical microkeratome flap creation.

    Science.gov (United States)

    Antonios, Rafic; Arba Mosquera, Samuel; Awwad, Shady T

    2015-08-01

    To evaluate and compare the refractive predictability and stability of laser in situ keratomileusis (LASIK) flap creation performed with a femtosecond laser and with a mechanical microkeratome to correct mild to moderate hyperopia. American University of Beirut Medical Center, Beirut, Lebanon. Retrospective case series. Patients who had hyperopic LASIK treatment using the Amaris excimer laser were included. Eyes in which the LDV femtosecond laser was used for flap creation were compared with eyes in which the Moria M2 microkeratome was used. The microkeratome group comprised 53 eyes and the femtosecond laser group, 72 eyes. Baseline characteristics were similar between groups (P > .05). The mean spherical equivalent (SE) deviation from target 1 week postoperatively was -0.08 diopter (D) ± 0.58 (SD) in the femtosecond laser group and -0.06 ± 0.87 D in the microkeratome group (P = .92). Thereafter, the mean SE deviation from target increased gradually and by 6 months postoperatively was +0.30 ± 0.50 D and +0.70 ± 0.71 D, respectively (P = .001). The correlation between the achieved and the attempted SE refraction was better in the femtosecond laser group (R(2) = 0.806) than the microkeratome group (R(2) = 0.671). Using the same nomogram, the short-term refractive outcomes of hyperopic LASIK with flap creation performed with the femtosecond laser were comparable to those for the microkeratome; however, the femtosecond group showed significantly better stability over the 6-month follow-up and better predictability, as reflected by a lower standard deviation and stronger Pearson correlation. Dr. Arba Mosquera is an employee of Schwind eye-tech-solutions GmbH and Co. KG. No other author has a financial or proprietary interest in any material or method mentioned. Copyright © 2015 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  2. Analysis on second operation after laser in situ keratomileusis

    Directory of Open Access Journals (Sweden)

    Wen-Xuan Pei

    2015-07-01

    Full Text Available AIM: To observe clinical effects between the laser in situ keratomileusis(LASIKsurgery and the laser subepithelial keratomileusis(LASEKsurgery as the second operation after an unsuccessful LASIK surgery. METHODS:Forty-nine patients(98 eyeswith refractive regression after LASIK operation received the second surgery. All patients were divided into two groups: group A and B. Group A(48 eyes of 24 patientsreceived LASIK surgery and group B(50 eyes of 25 patientsreceived LASEK surgery. Inspect the main parameters included visual acuity, refraction, corneal curvature, and the total value of high-aberration after 1wk, 1mo and 1a, t-test of groups was used as statistical analysis method.RESULTS: There was statistically significant(PP>0.05. There developed one case of epithelium in growth after LASIK surgery, and one case of haze Ⅱ after LASEK surgery. CONCLUSION: Both LASIK and LASEK surgery can obtain satisfactory therapeutic results after an unsuccessful LASIK surgery.

  3. Optic pit maculopathy after laser-assisted in situ keratomileusis.

    Science.gov (United States)

    Rodriguez-Coleman, Hanna; Schiff, William M; Hwang, John C; Speaker, Mark G

    2007-02-01

    Optic disc pit is an embryological malformation of the optic nerve that occurs in less than one in 10,000 people. It is 10%-15% bilateral, and 25% to 70% of patients develop a neurosensory macular detachment within the 2nd to 4th decade. We report a case of unilateral optic disc pit maculopathy 2 months after laser-assisted in situ keratomileusis (LASIK) revision.

  4. Epithelial healing and clinical outcomes in excimer laser photorefractive surgery following three epithelial removal techniques: mechanical, alcohol, and excimer laser.

    Science.gov (United States)

    Lee, Hyung Keun; Lee, Kyung Sub; Kim, Jin Kook; Kim, Hyeon Chang; Seo, Kyung Ryul; Kim, Eung Kweon

    2005-01-01

    To evaluate epithelial healing, postoperative pain, and visual and refractive outcomes after photorefractive keratectomy (PRK) using three epithelial removal techniques. Prospective, nonrandomized, comparative trial. Department of Ophthalmology, Yonsei University College of Medicine and Balgensesang Ophthalmology Clinic, Seoul, Korea. For the PRK procedure, the corneal epithelium was removed in one of three ways: mechanically (conventional PRK [PRK]) in 88 eyes of 44 patients; using excimer laser (transepithelial PRK [tPRK]) in 106 eyes of 53 patients; or using 20% diluted alcohol, laser-assisted subepithelial keratomileusis (LASEK) in 106 eyes of 53 patients. Epithelial healing, postoperative pain, uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), and remaining refractive error. The mean postoperative pain scores were 4.84 +/- 1.45 for PRK, 4.71 +/- 1.62 for tPRK, and 4.63 +/- 1.52 for LASEK (P = .125). The mean epithelial healing rates were 12.3 +/- 4.6 for PRK, 15.2 +/- 4.9 for tPRK, and 18.1 +/- 5.2 mm2/day for LASEK (P refractive outcomes. Using the same nomogram, tPRK resulted in a slight overcorrection, and LASEK resulted in a slight undercorrection.

  5. Investigation of excimer laser ablation of iron

    Science.gov (United States)

    Jordan, R.; Lunney, J. G.

    1998-05-01

    The excimer ablation of iron at 248 nm has been investigated by measuring the ablation depth and average ion energy as a function of laser fluence. Measurements have also been made of the laser transmission through the ablated vapour above the target. The absolute spectral intensity of the emission from the ablation plasma has been measured in both the vacuum ultraviolet and the visible. All results were compared with a simple numerical model describing the main physical processes involved in laser ablation of metal targets.

  6. Excimer laser irradiation of metal surfaces

    Science.gov (United States)

    Kinsman, Grant

    In this work a new method of enhancing CO2 laser processing by modifying the radiative properties of a metal surface is studied. In this procedure, an excimer laser (XeCl) or KrF) exposes the metal surface to overlapping pulses of high intensity, 10(exp 8) - 10(exp 9) W cm(exp -2), and short pulse duration, 30 nsec FWHM (Full Width Half Maximum), to promote structural and chemical change. The major processing effect at these intensities is the production of a surface plasma which can lead to the formation of a laser supported detonation wave (LSD wave). This shock wave can interact with the thin molten layer on the metal surface influencing to a varying degree surface oxidation and roughness features. The possibility of the expulsion, oxidation and redeposition of molten droplets, leading to the formation of micron thick oxide layers, is related to bulk metal properties and the incident laser intensity. A correlation is found between the expulsion of molten droplets and a Reynolds number, showing the interaction is turbulent. The permanent effects of these interactions on metal surfaces are observed through scanning electron microscopy (SEM), transient calorimetric measurements and Fourier transform infrared (FTIR) spectroscopy. Observed surface textures are related to the scanning procedures used to irradiate the metal surface. Fundamental radiative properties of a metal surface, the total hemispherical emissivity, the near-normal spectral absorptivity, and others are examined in this study as they are affected by excimer laser radiation. It is determined that for heavily exposed Al surface, alpha' (10.6 microns) can be increased to values close to unity. Data relating to material removal rates and chemical surface modification for excimer laser radiation is also discussed. The resultant reduction in the near-normal reflectivity solves the fundamental problem of coupling laser radiation into highly reflective and conductive metals such as copper and aluminum. The

  7. Vitreoretinal surgery for bilateral macular holes after laser-assisted in situ keratomileusis for the correction of myopia: a case report

    Directory of Open Access Journals (Sweden)

    García-Fernández Miriam

    2012-11-01

    Full Text Available Abstract Introduction Laser-assisted in situ keratomileusis surgery may induce postoperative changes in the vitreomacular interface due to the mechanical stretch of the vitreous produced by the suction ring and the shock waves generated by the excimer laser and, subsequently, may provoke macular hole formation. Case presentation A 53-year-old Spanish woman who had undergone a laser-assisted in situ keratomileusis for the correction of myopia in her right and left eye (10 years ago was referred to our department with a complaint of decreased visual acuity in both eyes. A fundoscopy and optical coherence tomography examination revealed a bilateral full-thickness macular hole. A 23-gauge sutureless pars plana vitrectomy was performed in both eyes, and 1 month after surgery her visual acuity improved and the hole closed. Conclusion The development of a bilateral full-thickness macular hole after laser-assisted in situ keratomileusis has been reported once. This case study enhances our understanding of the vitreoretinal pathology induced by laser-assisted in situ keratomileusis, showing the importance of a rigorous follow-up, because complications may occur even a decade later. In this case study we must also consider the contribution of the underlying myopia to the development of the bilateral macular holes.

  8. Bilateral Simultaneous Rhegmatogenous Retinal Detachment following Laser in situ Keratomileusis

    Directory of Open Access Journals (Sweden)

    Erhan Yumusak

    2016-06-01

    Full Text Available A 21-year-old woman developed simultaneous rhegmatogenous retinal detachment after laser in situ keratomileusis (LASIK in both eyes. She underwent pars plana vitrectomy surgery combined with endolaser photocoagulation and silicone oil tamponade in the right eye. A week later, pneumatic retinopexy was done in the left eye. As the retinal tear did not seal, 360° scleral buckling surgery was performed and retina was attached. Bilateral simultaneous rhegmatogenous retinal detachment after LASIK for correction of myopia can be a serious complication. Patients should be informed about the possibility of this complication.

  9. Fibrinous anterior uveitis following laser in situ keratomileusis

    Directory of Open Access Journals (Sweden)

    Parmar Pragya

    2009-01-01

    Full Text Available A 29-year-old woman who underwent laser in situ keratomileusis (LASIK for myopic astigmatism in both eyes presented with severe pain, photophobia and decreased visual acuity in the left eye eight days after surgery. Examination revealed severe anterior uveitis with fibrinous exudates in the anterior chamber, flap edema and epithelial bullae. Laboratory investigations for uveitis were negative and the patient required systemic and intensive topical steroids with cycloplegics to control the inflammation. This case demonstrates that severe anterior uveitis may develop after LASIK and needs prompt and vigorous management for resolution.

  10. Corneal biomechanical changes in eyes with small incision lenticule extraction and laser assisted in situ keratomileusis.

    Science.gov (United States)

    Osman, Ihab Mohamed; Helaly, Hany Ahmed; Abdalla, Moones; Shousha, Mohsen Abou

    2016-07-26

    Evaluating the corneal biomechanical changes using the Ocular Response Analyzer and the Corvis ST in eyes with incision lenticule extraction (SMILE) and laser assisted in situ keratomileusis (LASIK). This is a retrospective study that included 50 eyes equally divided into two groups. The first group included eyes that underwent SMILE procedure using VisuMax® 500 kHz laser system (Carl Zeiss Meditec, Jena, Germany) and the second group included eyes that underwent LASIK procedure using the EX500 Allegretto excimer laser platform (Wavelight GmbH, Erlangen, Germany). The Ocular Response Analyzer (ORA) and the Corvis ST (CST) measured the corneal biomechanical changes before and after the procedures. The ORA showed significant decrease of corneal hysteresis (CH) and corneal resistance factor (CRF) in both groups postoperatively. The percentage of change of CH and CRF were found to be significantly higher in group II. There was no significant difference in the IOP with the ORA and the CST pre and postoperatively in either group. Using CST, the deformation amplitude and HC peak distances increased significantly in both groups. It was also noted that the mean percentage of change of the deformation amplitude was nearly five times higher in group II than group I. Both LASIK and SMILE substantially decreased the corneal biomechanical properties with greater reduction in the LASIK group.

  11. Pupil response to tropicamide following laser in situ keratomileusis.

    Science.gov (United States)

    Chung, Hak Sung; Feder, Robert S

    2005-03-01

    To investigate the effect of corneal thinning after laser in situ keratomileusis (LASIK) on the corneal penetration of topical eye medication. Department of Ophthalmology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA. Laser in situ keratomileusis surgery was performed in 19 eyes of 10 patients enrolled in this prospective study. Measurements were made before surgery and 3 months postoperatively. After instillation of tropicamide 1%, the change in pupil size over time was measured with a Colvard pupillometer. Central corneal thickness (CCT) was measured with ultrasonic pachymetry before and 3 months after LASIK. The corneal epithelial condition was also examined by fluorescein dye staining. The mean CCT decreased significantly from 564 microm +/- 33 (SD) before LASIK surgery to 514 +/- 48 microm 3 months postoperatively (Ptropicamide 1% instillation was significantly larger 3 months after surgery than preoperatively (P=.0083, P=.0043, and P=.0144, respectively). The mean time to reach a pupil diameter of 6.0 mm decreased significantly from 14.4 +/- 4.3 minutes in preoperative eyes to 11.5 +/- 2.3 minutes in postoperative eyes (P=.0281). Mild punctate corneal epithelial staining (fewer than 5 spots) were observed in 4 eyes at the 3-month postoperative examination. Pupil dilation after tropicamide 1% instillation was significantly faster after LASIK surgery. Corneal thinning that resulted from LASIK enhanced corneal penetration of tropicamide 1%.

  12. Subpicosecond, high-brightness excimer laser systems

    Energy Technology Data Exchange (ETDEWEB)

    Taylor, A.J.; Gosnell, T.R.; Roberts, J.P.; Lester, C.S.; Gibson, R.B.; Harper, S.E.; Tallman, C.R.

    1988-01-01

    Subpicosecond, high-brightness excimer laser systems are being used to explore the interaction of intense coherent ultraviolet radiation with matter. Applications of current systems include generation of picosecond x-ray pulses, investigation of possible x-ray laser pumping schemes, studies of multiphoton phenomena in atomic species, and time-resolved photochemistry. These systems, based on the amplification of subpicosecond pulses in small aperture (/approximately/1 cm/sup 2/) XeCl or KrF amplifiers, deliver focal spot intensities of /approximately/10/sup 17/ W/cm/sup 2/. Scaling to higher intensities, however, will require an additional large aperture amplifier which preserves near-diffraction-limited beam quality and subpicosecond pulse duration. We describe here both a small aperture KrF system which routinely provides intensities >10/sup 17/ W/cm/sup 2/ to several experiments, and a large aperture XeCl system designed to deliver /approximately/1 J subpicosecond pulses and yield intensities on target in excess of 10/sup 19/W/cm/sup 2/. We also discuss the effects of two-photon absorption on large-aperture, high-brightness excimer lasers. 4 refs., 2 figs.

  13. Electrodeless excimer laser; Laser a eccimeri senza elettrodi

    Energy Technology Data Exchange (ETDEWEB)

    Lisi, N. [ENEA, Divisione Nuovi Materiali, Centro Ricerche Casaccia, Rome (Italy)

    2001-07-01

    In this paper it is proposed how to build an excimer laser based on an electrodeless discharge (or Dielectric Barrier Discharge). Such laser could operate with a low energy per pulse (<100 mJ) and a high repetition rate (<100 kHz). The most relevant advantage an electrodeless DBD laser is the much longer gas mixture lifetime. This feature could allow the operation of a sealed laser emitting higher average power with respect to commercially available excimer lasers. Such discharge scheme could be advantageous in order to excite the F{sub 2} excimer molecule, whose emission wavelength in the VUV range (157 nm) at high reprate is particularly interesting in the micro-lithography field. [Italian] In questo documento viene proposto come costruire un laser a eccimeri basato su una scarica priva di elettrodi, o Dielectric Barrier Discharge. Tale laser puo' funzionare con una bassa energia per impulso (<100 mJ) ad alta frequenza di ripetizione (<100 kHz). Il vantaggio fondamentale di un laser a DBD e quindi privo di elettrodi e' la vita media della miscela gassosa molto piu' alta che potrebbe permettere alla camera laser di operare sigillata ad una potenza media superiore a quella dei laser a eccimeri attuali. Tale schema di pompaggio potrebbe essere particolarmente vantaggioso per eccitare la molecola eccimero F{sub 2} la cui lunghezza di emissione nel VUV (157 nm) ad elevata frequenza di ripetizione presenta un notevole interesse nel campo della produzione di microcircuiti.

  14. Excimer laser phototherapeutic keratectomy for keratoconus nodules.

    Science.gov (United States)

    Elsahn, Ahmed F; Rapuano, Christopher J; Antunes, Victor A; Abdalla, Yasmine F; Cohen, Elisabeth J

    2009-02-01

    To report the outcomes of contact lens-intolerant patients with keratoconus (KCN) with subepithelial nodules treated with excimer laser phototherapeutic keratectomy (PTK). The charts of all contact lens-intolerant patients with KCN who underwent excimer laser PTK for subepithelial nodules were identified using a computer database and were retrospectively reviewed. Preoperative and postoperative visual acuity and method of correction, surgical treatment, epithelial healing, complications, and KCN nodule recurrence were all analyzed. Fifteen eyes of 15 patients with a minimum follow-up of 3 months were reviewed. Mean follow-up time was 23.1 months (SD +/- 42.5 months, range 3-143 months). In 9 eyes, the epithelial defect healed by postoperative day 3 and all eyes healed by postoperative day 6. There was no infection or corneal melting in any of the eyes. After PTK, 11 patients were refit successfully with rigid gas-permeable contact lenses and 4 wore glasses. Three patients had a recurrence of the KCN nodule at 3, 8, and 23 months postoperatively. One of them had a repeat PTK 23 months after the initial surgery, improving to 20/40 with contact lenses at 55 months postoperatively. Another patient decided to have a penetrating keratoplasty, and the third patient is considering repeat PTK or penetrating keratoplasty. PTK effectively removed KCN nodules without recurrences in most patients and can be a successful modality to improve contact lens tolerance and delay or avoid more invasive surgery.

  15. Effects of laser in situ keratomileusis (LASIK) on corneal biomechanical measurements with the Corvis ST tonometer.

    Science.gov (United States)

    Frings, Andreas; Linke, Stephan J; Bauer, Eva L; Druchkiv, Vasyl; Katz, Toam; Steinberg, Johannes

    2015-01-01

    This study was initiated to evaluate biomechanical changes using the Corvis ST tonometer (CST) on the cornea after laser in situ keratomileusis (LASIK). University Medical Center Hamburg-Eppendorf, Germany, and Care Vision Refractive Centers, Germany. Retrospective cohort study. This retrospective study included 37 eyes of 37 refractive patients. All CST measurements were performed 1 day before surgery and at the 1-month follow-up examination. The LASIK procedure included mechanical flap preparation using a Moria SBK microkeratome and an Allegretto excimer laser platform. Statistically significant differences were observed for mean first applanation length, mean first and second deflection lengths, mean first and second deflection amplitudes, radius of curvature, and peak distance. Significant positive correlations were found between the change (Δ) of radius of curvature and manifest refraction spherical equivalent (MRSE), ablation depth, and Δintraocular pressure as well as between AD and ΔHC-time. Each diopter of myopic correction in MRSE resulted in an increase in Δradius of curvature of 0.2 mm. Several CST parameters were statistically significantly altered by LASIK, thereby indicating that flap creation, ablation, or both, significantly change the ability of the cornea to absorb or dissipate energy.

  16. Differences in the early biomechanical effects of hyperopic and myopic laser in situ keratomileusis.

    Science.gov (United States)

    de Medeiros, Fabricio Witzel; Sinha-Roy, Abhijit; Alves, Milton Ruiz; Wilson, Steven E; Dupps, William J

    2010-06-01

    To compare changes in corneal hysteresis (CH) and the corneal resistance factor (CRF) in myopic and hyperopic laser in situ keratomileusis (LASIK) and evaluate their relationship to the number of photoablative pulses delivered, a surrogate for ablation volume. Cleveland Clinic Cole Eye Institute, Cleveland, Ohio, USA. Preoperative and 1-week postoperative Ocular Response Analyzer measurements in eyes that had femtosecond-assisted LASIK were studied retrospectively. Changes in CH and CRF were compared and tested for correlation with the number of excimer laser pulses. Thirteen myopic eyes and 11 hyperopic eyes were evaluated. Preoperative corneal thickness, CH, CRF, programmed correction magnitude, flap thickness, and total number of fixed spot-size photoablative pulses were similar in the 2 groups (P>.1). Decreases in CH and CRF were greater after myopic LASIK than after hyperopic LASIK (Pbiomechanical status, ablation volume, and the spatial distribution of ablation are important factors that affect corneal resistance and viscous dissipative properties differently. Preferential tissue removal in the natively thicker paracentral cornea in hyperopia may partially account for the rarity of ectasia after hyperopic LASIK. (c) 2010 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  17. Excimer Lasers With Capacitively Excited Tubular Discharges

    Science.gov (United States)

    Eichler, Hans J.; Herweg, Helmut; de la Rosa, Jose

    1989-04-01

    The excitation of excimer lasers in tubular discharges results in simple and compact devices needing no preionization. Optical output energies are in the millijoule range. We investigated XeF, KrF and ArF lasers for various operating conditions. The lasers consist of capillary glass tubes with two internal electrodes at the ends and an aluminium-foil wrapped around the tube as capacitive electrode. A maximum output energy of 0.3 mJ has been achieved for the XeF laser. The good quality of the discharge is indicated by the observation of spontaneous mode locking. The detailed study of the discharge for different polarities of the electrodes has shown that efficient operation with a high gas lifetime can be obtained by a purely capacitively excited discharge. A gas lifetime of about 10,000 pulses for 3 litres gas mixture has been observed. Using a two stage Marx generator to generate 100 kV excitation voltage a maximum output energy of 0.7 mJ was obtained for a gas mixture of Kr, F2 and He with an efficiency of 0.17%. The KrF laser operates also without the buffer gas. Laser action in ArF has been achieved with 15 μJ pulse energy and 10 ns duration.

  18. Posterior Corneal Surface Stability after Femtosecond Laser-Assisted Keratomileusis

    Directory of Open Access Journals (Sweden)

    Carlo Cagini

    2015-01-01

    Full Text Available The purpose of this study was to evaluate posterior corneal surface variation after femtosecond laser-assisted keratomileusis in patients with myopia and myopic astigmatism. Patients were evaluated by corneal tomography preoperatively and at 1, 6, and 12 months. We analyzed changes in the posterior corneal curvature, posterior corneal elevation, and anterior chamber depth. Moreover, we explored correlation between corneal ablation depth, residual corneal thickness, percentage of ablated corneal tissue, and preoperative corneal thickness. During follow-up, the posterior corneal surface did not have a significant forward corneal shift: no significant linear relationships emerged between the anterior displacement of the posterior corneal surface and corneal ablation depth, residual corneal thickness, or percentage of ablated corneal tissue.

  19. Stability of the laser in situ keratomileusis corneal flap in rabbit eyes.

    Science.gov (United States)

    Laurent, John M; Schallhorn, Steven C; Spigelmire, Jennifer R; Tanzer, David J

    2006-06-01

    To quantify the force required to dislodge a laser in situ keratomileusis (LASIK) corneal flap in rabbits and correlate that force with sources of injury to LASIK corneal flaps in humans. Animal Vivarium and Department of Ophthalmology, Naval Medical Center, San Diego, California, USA. Corneal flaps were cut in 56 eyes of 30 rabbits. A -8.00 diopter excimer ablation was also performed in 32 of the eyes. Injury testing, using a burst of CO2 from a modified paintball gun, was conducted from 1 to 9 days postoperatively. Impact force was compared to that generated by mechanical trauma (fingers and a small tree branch) striking a force gauge. Of 43 eyes tested for injury, flaps could not be dislocated in 11 eyes (26%). There was no significant difference between eyes treated with flap only and those that also had ablation. When flaps were dislodged, the required force generally resulted in extensive intraocular injury. There was no significant difference between the force required for flap dislocation on postoperative days 1 and 9. In rabbits, LASIK corneal flaps were very resistant to high-speed wind trauma as early as 24 hours postoperatively. Flap stability was robust prior to the formation of collagen scar tissue, probably due to epithelial bridging at the edge of the flap and an osmotic gradient across the flap-stromal bed interface. Although this study used a rabbit model, it seems likely that both these flap adhesion mechanisms would also provide stability to the LASIK flap in humans.

  20. [Glycosaminoglycans in subepithelial opacity after excimer laser keratectomy].

    Science.gov (United States)

    Nakayasu, K; Gotoh, T; Ishikawa, T; Kanai, A

    1996-05-01

    We evaluated histochemically the characteristics of glycosaminoglycans and proteoglycans in the corneal subepithelial opacity after excimer laser keratectomy on rabbit corneas. We also performed the same evaluations on the cornea after mechanical keratectomy. Twenty days after the operations, the area immediately subjacent to the epithelium showed strong staining with toluidine blue, alcian blue, and colloidal iron. However, after treatment with chondroitinase ABC or chondroitinase AC, alcian blue staining in this area decreased dramatically. Antilarge proteoglycan antibody also reacted strongly in this area. Histochemical and immunohistochemical examination of the cornea where mechanical keratectomy was done showed basically similar findings with the cornea of excimer laser keratectomy. These results suggest that large-molecula proteoglycans with chondroitine sulfate side chains become localized in the subepithelial area after two different kinds of keratectomies. We presume from histochemical and immunohistochemical observations that the subepithelial opacity observed after excimer laser keratectomy is not a special reaction to excimer laser but simply a corneal scar formed after stromal resection.

  1. Ignition by excimer laser photolysis of ozone

    Science.gov (United States)

    Lucas, D.; Dunn-Rankin, D.; Hom, K.; Brown, N. J.

    1986-10-01

    We have ignited mixtures of hydrogen, oxygen, and ozone in closed cells with 248 nm radiation from a KrF excimer laser. Ozone, the only significant absorber in this system, absorbs a single photon and produces oxygen atoms which initiate combustion. A discretized, time-dependent Beer's law model is used to demonstrate that the radical concentration immediately after photolysis is a function of laser power, ozone concentration, focal length, and separation between the lens and reaction cell. Spark schileren photographs are used to visualize the ignition events and identify the ignition sites. The effects of equivalence ratio, pressure, and the initial gas temperature on the minimum ozone concentration needed to produce ignition are presented, and only the initial temperature has a significant effect. Modelling studies of the ignition process aid in the interpretation of the experimental results, and show that the ignition we observe is not due solely to thermal effects, but is strongly dependent on the number and type of radicals present initially after photolysis. Ignition using other hydrocarbons as fuels was also demonstrated.

  2. Traumatic corneal flap displacement after laser in situ keratomileusis (LASIK

    Directory of Open Access Journals (Sweden)

    Tsai TH

    2017-04-01

    Full Text Available Tsung-Han Tsai,1 Kai-Ling Peng,1 Chien-Jen Lin2 1Department of Ophthalmology, 2Department of Radiology, Chi Mei Medical Center, Tainan, Taiwan Background: Laser in situ keratomileusis (LASIK is the most common and popular procedure performed for the correction of refractive errors in the last two decades. We report a case of traumatic flap displacement with flap folding which occurred 3 years after LASIK was performed. Previous literature suggests that vision prognosis would be closely related to proper and prompt management of traumatic flap displacement with flap folding 3 years after LASIK.Case presentation: A 23-year-old female presented to our hospital who had undergone uneventful LASIK in both eyes 3 years prior. Unfortunately, she had suffered a blunt trauma in her right eye in a car accident. A late onset of corneal flap displacement was found with upper and lower portion of the flap being folded inside the corneal bed. Surgical intervention for debridement with subsequent reposition of corneal flap was performed as soon as possible in the operating room. A bandage contact lens was placed, and topical antibiotic and corticosteroids were given postoperatively. Two days after the operation, the displaced corneal flap was found to be well attached smoothly on the corneal bed without folds. The best-corrected visual acuity was 6/6 with refraction of −0.75 D to 1.0 D ×175° in her right eye 1 month later.Literature review: We reviewed a total of 19 published cases of late-onset traumatic flap dislocations or displacements after LASIK with complete data from 2000 to 2014.Conclusion: Traumatic displacement of corneal flaps after LASIK may occur after blunt injury with specific direction of force to the flap margin, especially tangential one. According to the previous literature, late-onset traumatic flap displacement may happen at any time after LASIK and be caused by various types of injuries. Fortunately, good visual function could

  3. The Excimer Laser: Its Impact on Science and Industry

    Science.gov (United States)

    Basting, Dirk

    2010-03-01

    After the laser was demonstrated in 1960, 15 years were required to develop a practical method for extending laser emission into the UV: the Excimer laser. This historical review will describe the challenges with the new medium and provide an insight into the technological achievements. In the transition from Science to Industry it will be shown how start-ups successfully commercialized laboratory prototypes. The pioneers in this rapidly expanding field will be identified and the influence of government-funded research as well as the role of venture capital will be discussed. In scientific applications, the fields of photochemistry and material research were particularly stimulated by the advent of a reliable UV light source. Numerous industrial applications and worldwide research in novel applications were fueled In the early and mid 80's by progress in excimer laser performance and technology. The discovery of ablative photocomposition of polymer materials by Srinivasan at IBM opened the door to a multitude of important excimer applications. Micromachining with extreme precision with an excimer laser enabled the success of the inkjet printer business. Biological materials such as the human cornea can also be ``machined'' at 193nm, as proposed in 1983 by Trokel and Srinivasan. This provided the foundation of a new medical technology and an industry relying on the excimer laser to perform refractive surgery to correct vision Today, by far the largest use of the excimer laser is in photolithography to manufacture semiconductor chips, an application discovered by Jain at IBM in the early 80's. Moore's law of shrinking the size of the structure to multiply the number of transistors on a chip could not have held true for so long without the deep UV excimer laser as a light source. The presentation will conclude with comments on the most recent applications and latest market trends.

  4. Effects of laser in situ keratomileusis (LASIK on corneal biomechanical measurements with the Corvis ST tonometer

    Directory of Open Access Journals (Sweden)

    Frings A

    2015-02-01

    Full Text Available Andreas Frings,1,* Stephan J Linke,1,2,* Eva L Bauer,1 Vasyl Druchkiv,1 Toam Katz,1,2 Johannes Steinberg1,2 1Department of Ophthalmology, University Medical Center Hamburg-Eppendorf (UKE, Hamburg, Germany; 2Care Vision Refractive Center, Hamburg, Germany *These authors contributed equally to this work Purpose: This study was initiated to evaluate biomechanical changes using the Corvis ST tonometer (CST on the cornea after laser in situ keratomileusis (LASIK. Setting: University Medical Center Hamburg-Eppendorf, Germany, and Care Vision Refractive Centers, Germany. Design: Retrospective cohort study. Methods: This retrospective study included 37 eyes of 37 refractive patients. All CST measurements were performed 1 day before surgery and at the 1-month follow-up examination. The LASIK procedure included mechanical flap preparation using a Moria SBKmicrokeratome and an Allegretto excimer laser platform. Results: Statistically significant differences were observed for mean first applanation length, mean first and second deflection lengths, mean first and second deflection amplitudes, radius of curvature, and peak distance. Significant positive correlations were found between the change (∆ of radius of curvature and manifest refraction spherical equivalent (MRSE, ablation depth, and ∆intraocular pressure as well as between AD and ∆HC-time. Each diopter of myopic correction in MRSE resulted in an increase in ∆radius of curvature of 0.2 mm. Conclusion: Several CST parameters were statistically significantly altered by LASIK, thereby indicating that flap creation, ablation, or both, significantly change the ability of the cornea to absorb or dissipate energy. Keywords: LASIK, corneal biomechanics, refractive surgery, Corvis ST

  5. Analysis of ectasia after laser in situ keratomileusis: risk factors.

    Science.gov (United States)

    Binder, Perry S

    2007-09-01

    To examine a database of laser in situ keratomileusis (LASIK) procedures for preoperative and operative factors assumed to increase the risk for developing post-LASIK ectasia. Private clinical practice. A computer database was queried for eyes that had LASIK for myopic refractive errors with the following characteristics: preoperative corneal thickness 500 microm or less, mean keratometry greater than 47.0 diopters (D), patient age 25 years or younger, attempted correction greater than -8.0 D, refractive astigmatism not with-the-rule and greater than 2.0 D, and residual stromal bed thickness (RST) 250 microm or less. Flap thickness and RST were measured using ultrasound pachymetry. All recorded information was exported to MS Excel and analyzed for eyes that had ectasia. Of the 9700 eyes in the database, none with the above characteristics developed ectasia over mean follow-up periods exceeding 2 years. Seven eyes had multiple risk factors without ectasia. Three eyes with abnormal preoperative topography developed ectasia. Individual preoperative and operative factors did not in and of themselves increase the risk for ectasia. Unmeasured and unknown factors that affect the individual cornea's biomechanical stability, in combination with some suspected risk factors as well as the current inability to identify corneas at risk for developing ectatic disorders, probably account for most eyes that develop ectasia today.

  6. Laser in-situ keratomileusis after penetrating keratoplasty.

    Science.gov (United States)

    Vajpayee, Rasik B; Sharma, Namrata; Sinha, Rajesh; Bhartiya, Prashant; Titiyal, Jeewan S; Tandon, Radhika

    2003-01-01

    Laser in situ keratomileusis (LASIK) after penetrating keratoplasty has been used more commonly for the correction of myopia or myopic astigmatism and less so for hypermetropia or hyperopic astigmatism. The primary goal after LASIK in such cases is resolution of sufficient myopia and astigmatism to allow spectacle correction of the residual refractive error and decrease anisometropia. All sutures should be removed prior to LASIK and the interval between penetrating keratoplasty and LASIK should be a minimum of 1 year. Preoperative evaluation includes refraction, slit-lamp biomicroscopy, corneal topography, and specular microscopy. The technique of LASIK surgery after penetrating keratoplasty is similar to the standard procedure. However, many variations have been described. These include maneuvers during surgery such as augmentation with arcuate cuts on the stromal bed and topographically guided LASIK. Other variations are relaxing incisions followed by LASIK surgery and sequential treatment by LASIK, that is, raising of the flap as a first stage procedure followed by ablation if required, 4 to 6 weeks later after relifting the flap in the second stage. Improvement in both uncorrected visual acuity and spectacle-corrected visual acuity, as well as a decrease in spherical equivalent, cylinder, and anisometropia, has been reported in various studies. All grafts were clear and no occurrence of wound dehiscence has been reported. Intraoperative complications include hemorrhage, microkeratome failure, flap buttonhole, dislocation, and perforation. Postoperative complications include undercorrection, decentered ablation, and regression. Re-enhancements after LASIK following keratoplasty are possible with acceptable visual outcome.

  7. Antiglaucoma drugs for achieving monovision after laser in situ keratomileusis

    Directory of Open Access Journals (Sweden)

    Kazutaka Kamiya

    2009-02-01

    Full Text Available Kazutaka Kamiya, Kimiya ShimizuDepartment of Ophthalmology, University of Kitasato School of Medicine, JapanAbstract: We report on a patient in whom the use of antiglaucoma drugs has been beneficial for the attainment of monovision after laser in situ keratomileusis (LASIK. A 57-year-old woman undergoing LASIK complained of blurred vision in the right eye. After a successful trial of monovision with contact lenses, antiglaucoma drugs (2.5% nipradilol were administered topically to the right eye twice a day to establish monovision. In the right eye, the manifest refraction was changed from −4.0, −1.0 × 80, with an uncorrected visual acuity (UCVA of 0.3 for near vision before treatment, to −2.5, −1.0 × 80, with an UCVA of 0.9 for near vision after treatment, while, in the left eye, it was 0, −1.0 × 100, with an UCVA of 0.9 for far vision. Binocular UCVA was improved from 0.3 for near and 0.9 for distance vision before treatment, to 0.9 for near and 1.0 for distance vision after treatment. No complications were observed and the manifest refraction remained stable during the 6-month follow-up period. The use of antiglaucoma drugs may be helpful for the achievement of monovision by reduction of myopic regression after LASIK.Keywords: antiglaucoma drugs, regression, monovision, LASIK

  8. Long-term comparison of corneal aberration changes after laser in situ keratomileusis: mechanical microkeratome versus femtosecond laser flap creation.

    Science.gov (United States)

    Muñoz, Gonzalo; Albarrán-Diego, César; Ferrer-Blasco, Teresa; García-Lázaro, Santiago; Cerviño-Expósito, Alejandro

    2010-11-01

    To compute and compare visual acuity, refractive outcomes, and anterior corneal aberration changes after myopic laser in situ keratomileusis (LASIK) with flap creation by a mechanical microkeratome and by a femtosecond laser. Private practice refractive surgery center, Valencia, Spain. Comparative case series. Patients were assigned to have LASIK flap creation with a mechanical microkeratome (Carriazo-Barraquer) or a femtosecond laser (IntraLase). The Visx S2 excimer laser was used for myopic ablation in all cases. Main outcome measures included uncorrected and corrected distance visual acuities and the defocus equivalent. Higher-order aberrations (HOAs) were computed from the anterior corneal surface measured with topography for 4.0 mm and 6.0 mm pupil diameters before and 48 months after surgery. The study evaluated 50 patients (98 eyes). The root mean square of HOAs increased postoperatively by a factor of approximately 1.9 in both groups and with both pupil diameters. There were no statistically significant differences between the 2 groups in the increase in anterior corneal aberrations, mean postoperative visual acuity, or residual refraction. All visual and optical performance metrics remained stable throughout the 4-year follow-up. There were no complications with flap creation and no postoperative complications. The increase in anterior corneal aberrations after myopic LASIK was similar after mechanical microkeratome and femtosecond laser flap creation. Visual acuity, refraction, and the optical quality of the cornea after LASIK remained stable through 4 years postoperatively in both groups. Copyright © 2010 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  9. Measurement of corneal curvature change after mechanical laser in situ keratomileusis flap creation and femtosecond laser flap creation.

    Science.gov (United States)

    Ortiz, Dolores; Alió, Jorge L; Piñero, David

    2008-02-01

    To compare the change in corneal curvature from the predicted surgical radius (sculpted in the corneal stroma) and the measured postoperative radius of the first surface of the cornea after laser in situ keratomileusis (LASIK) for myopia correction using 2 methods of flap creation: mechanical microkeratome and femtosecond laser. Vissum-Instituto Oftalmológico de Alicante, Alicante, Spain. This retrospective consecutive nonrandomized comparative interventional case series included 85 eyes with myopia or myopic astigmatism treated using the Esiris excimer laser (Schwind). Patients were divided into 2 groups. One group had LASIK with an M2 microkeratome (Moria) (mechanical LASIK group) and the other, with a femtosecond laser (IntraLase FS, IntraLase Corp.) (femtosecond LASIK group). The relationship between the postsurgical corneal radius and the predicted sculpted radius as well as the mean value of the percentage change in the curvature radius were analyzed to obtain the effect on the refractive defect in each group. There were 44 eyes in the mechanical LASIK group and 41 eyes in the femtosecond LASIK group. A high correlation was found between the final corneal radius and the predicted sculpted radius in both groups (r(2) = 0.85). The mean percentage change in the curvature radius was -3.6% in the mechanical LASIK group and -1.6% in the femtosecond LASIK group (Prefractive change was 1.2 diopters (D) and 0.8 D, respectively. The refractive change in corneal curvature, which related to the biomechanical response of the corneal surface after the flap cut and repositioning, was lower after femtosecond laser LASIK than after LASIK performed using a mechanical microkeratome. Estimations of refractive change induced by this response should be taken into account in surgery design.

  10. Comparative shock wave analysis during corneal ablation with an excimer laser, picosecond laser, and femtosecond laser

    Science.gov (United States)

    Krueger, Ronald R.; Juhasz, Tibor

    1995-05-01

    With the event of topographic steep central islands following excimer laser surgery and the potential damage to the corneal endothelium, shock waves are playing an increasingly important role in laser refractive surgery. With this in mind, we performed a comparative shock wave analysis in corneal tissue using an excimer laser, picosecond laser, and femtosecond laser. We used a Lambda Physik excimer laser at 308 nm wavelength, a Nd:YLF picosecond laser at 1053 nm wavelength and a synchronously pumped linear cavity femtosecond laser at 630 nm wavelength. The pulse widths of the corresponding lasers were 8 ns, 18 ps, 150 fs, respectively. The energy density of irradiation was 2.5 to 8 times the threshold level being 2 J/cm2 (excimer laser), 86 J/cm2 (picosecond laser) and 10.3 J/cm2 (femtosecond laser). Shock wave dynamics were analyzed using time-resolved photography on a nanosecond time scale using the picosecond laser in corneal tissue, water and air. Shock wave dynamics using the femtosecond laser were studied in water only while the excimer laser induced shock wave during corneal ablation was studied in air only. We found the dynamics of shock waves to be similar in water and corneal tissue indicating that water is a good model to investigate shock wave effects in the cornea. The magnitude of the shock wave velocity and pressure decays over time to that of a sound wave. The distance over which it decays is 3 mm in air with the excimer laser and 600 - 700 micrometers in air with the picosecond laser. In water, the picosecond laser shock wave decays over a distance of 150 micrometers compared to the femtosecond laser shock wave which decays over a distance of 30 micrometers . Overall the excimer laser shock wave propagates 5 times further than that of the picosecond laser and the picosecond laser shock wave propagates 5 times further than that of the femtosecond laser. In this preliminary comparison, the time and distance for shock wave decay appears to be directly

  11. Overview on the high power excimer laser technology

    Science.gov (United States)

    Liu, Jingru

    2013-05-01

    High power excimer laser has essential applications in the fields of high energy density physics, inertial fusion energy and industry owing to its advantages such as short wavelength, high gain, wide bandwidth, energy scalable and repetition operating ability. This overview is aimed at an introduction and evaluation of enormous endeavor of the international high power excimer laser community in the last 30 years. The main technologies of high power excimer laser are reviewed, which include the pumping source technology, angular multiplexing and pulse compressing, beam-smoothing and homogenous irradiation, high efficiency and repetitive operation et al. A high power XeCl laser system developed in NINT of China is described in detail.

  12. New Class of Excimer-Pumped Atomic Lasers (XPALS)

    Science.gov (United States)

    2017-01-27

    AFRL-AFOSR-VA-TR-2017-0019 New Class of Excimer-Pumped Atomic Lasers (XPALS) James Eden UNIVERSITY OF ILLINOIS CHAMPAIGN 506 S WRIGHT ST 364 HENRY...TITLE AND SUBTITLE New Class of Excimer-Pumped Atomic Lasers (XPALS) 5a. CONIKA\\.INUMBER FA9550-13- 1-0006 5b.GRANT NUMBER Sc. f’ftOGRAM ELEMENT...cxcitcd state-excited state reaction rates. We ore pleased to report that the main goal orthis program, the viability of nn atomic laser having a

  13. Excimer laser interaction with dentin of the human tooth

    Science.gov (United States)

    Hammond, Ernest C., Jr.; Gilliam, Ruth L.; Baker, George R.

    1989-01-01

    The use an excimer laser produced many unusual conical structures within the dentin of the inner part of the human tooth. By varying the frequency of the laser one can disperse the energy and cause more bleeding in laser surgery, but not destroy the cells associated with the incision. Therefore, the healing process will virtually be without scarring. Whereas, using the infrared laser the blood loss would be less, but the healing process would tend to be longer because cells are being destroyed due to the cauterization effect of the laser. The question is, are these structures produced as an interaction with the laser or are they an intrinsic part of the structure. The effects of the laser interaction upon dentin was studied, and in using electron microscopy the interaction of the excimer laser upon the tooth dentin and other various biological tissue is more clearly understood.

  14. Laser in situ keratomileusis in adult patients with anisometropic amblyopia

    Directory of Open Access Journals (Sweden)

    Dilek Yaşa

    2013-06-01

    Full Text Available AIM: To evaluate the increase in corrected distance visual acuity (CDVA after laser in situ keratomileusis (LASIK in adults with anisometropic amblyopia.METHODS: The medical records of consecutive patients diagnosed with anisometropic amblyopia at the time of refractive evaluation who underwent LASIK were retrospectively reviewed. Patients with at least a two-line difference of visual acuity (VA between the eyes with a spherical refractive error difference of at least 3.00 diopters (D or an astigmatic difference of at least 2.00D were included. Patients with any other possible reason for amblyopia other than anisometropia or those who had undergone previous amblyopia treatment were excluded. Amblyopic eyes with myopia or myopic astigmatism were considered as group 1, hypermetropia or hypermetropic astigmatism constituted group 2, and mixed astigmatism patients comprised group 3. Uncorrected distance visual acuity (UDVA, subjective manifest refraction, and CDVA were analyzed at 1 week and 1 month, 3, and 6 months. RESULTS: The study included 57 eyes of 57 patients. There were 33 eyes in group 1, 12 eyes in group 2, and 12 eyes in group 3. The preoperative mean values for spherical equivalent of subjective manifest refraction (SE in groups 1, 2, and 3 were (-4.66±1.97D, (4.40±1.00D, and (0.15±1.05D, respectively. Mean CDVA improved 0.1 log units (1 line LogMAR at 6 months (P0.05. Moreover, age, the amount of preoperative refractive error, and the levels of preoperative corrected and UDVA had no effect on postoperative CDVA improvement (P>0.05.CONCLUSION: Correction of refractive errors with LASIK produced significant CDVA improvement in adult patients with anisometropic amblyopia and no previous amblyopia treatment.

  15. [Traumatic flap dislocation after laser in situ keratomileusis].

    Science.gov (United States)

    Hori-Komai, Yoshiko; Toda, Ikuko; Yamamoto, Takahiro; Sakatani, Keiko; Asano-Kato, Naoko; Fukumoto, Teruki; Arai, Hiroyuki; Tsubota, Kazuo

    2008-05-01

    To report our experience in treating cases of flap dislocation caused by trauma after laser in situ keratomileusis (LASIK). We did a retrospective review of the case records of 16,319 patients (31,655 eyes) who underwent LASIK in Minamiaoyama Eye Clinic. Ten eyes of 9 patients were treated for flap dislocation. Conditions of the trauma occurrence, main findings of the eyes, treatments and clinical results are described. Dislocation occurred during a period of 5 days to 4 years after LASIK. Accidents happened when working, when playing with children or pets, or when fighting. The main findings were folds or microstriae, diffuse lamellar keratitis (DLK), and epithelial ingrowth, including partial splitting of the flap (1 eye) and only a crack in the epithelium of the flap edge (1 eye). Seven flaps were lifted, irrigated and repositioned, and observed after fitting the patients with soft contact lenses. Three flaps were treated with eye drops of hyaluronic acid only, or with systemic steroids, topical steroids, and antibiotics. Uncorrected visual acuity recovered to more than 1.0 in 7 eyes, and best corrected visual acuity (BCVA) was more than 1.0 in all eyes. However, 3 eyes lost one line and 1 eye lost two lines of BCVA. Many cases of flap dislocation showed recovery of good visual acuity with adequate and prompt treatment. However, it is possible to leave irregular astigmatism untreated which has a bad effect on visual acuity, depending on the affected part and the seriousness of the injury. The connection between patient and clinic is important for proper and prompt treatment.

  16. Comparison of efficacy and safety of laser in situ keratomileusis using 2 femtosecond laser platforms in contralateral eyes.

    Science.gov (United States)

    Rosman, Mohamad; Hall, Reece C; Chan, Cordelia; Ang, Andy; Koh, Jane; Htoon, Hla Myint; Tan, Donald T H; Mehta, Jodhbir S

    2013-07-01

    To compare the efficacy, predictability, and refractive outcomes of laser in situ keratomileusis (LASIK) using 2 femtosecond platforms for flap creation. Multisurgeon single center. Clinical trial. Bilateral femtosecond LASIK was performed using the Wavelight Allegretto Eye-Q 400 Hz excimer laser system. The Visumax femtosecond platform (Group 1) was used to create the LASIK flap in 1 eye, while the Intralase femtosecond platform (Group 2) was used to create the LASIK flap in the contralateral eye. The preoperative, 1-month, and 3-month postoperative visual acuities, refraction, and contrast sensitivity in the 2 groups were compared. The study enrolled 45 patients. Three months after femtosecond LASIK, 79.5% of eyes in Group 1 and 82.1% in Group 2 achieved an uncorrected distance visual acuity of 20/20 (P=.808). The mean efficacy index was 0.97 in Group 1 and 0.98 in Group 2 at 3 months (P=.735); 89.7% of eyes in Group 1 and 84.6% of eyes in Group 2 were within ± 0.50 diopter of emmetropia at 3 months (P=.498). No eye in either group lost more than 2 lines of corrected distance visual acuity. The mean safety index at 3 months was 1.11 in Group 1 and 1.10 in Group 2 (P=.570). The results of LASIK with both femtosecond lasers were similar, and both platforms produced efficacious and predictable LASIK outcomes. No author has a financial or proprietary interest in any material or method mentioned. Copyright © 2013 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  17. Topographic steep central islands following excimer laser photorefractive keratectomy

    Science.gov (United States)

    Krueger, Ronald R.; McDonnell, Peter J.

    1994-06-01

    The purpose of this study is to demonstrate that topographic irregularities in the form of central islands of higher refractive power can be seen following excimer laser refractive surgery. We reviewed the computerized corneal topographic maps of 35 patients undergoing excimer laser PRK for compound myopic astigmatism or anisometropia from 8/91 to 8/93 at the USC/Doheny Eye Institute. The topographic maps were generated by the Computed Anatomy Corneal Modeling System, and central islands were defined as topographic areas of steepening of at least 3 diopters and 3 mm in diameter. A grading system was developed based on the presence of central islands during the postoperative period. Visually significant topographic steep central islands may be seen in over 50% of patients at 1 month following excimer laser PRK, and persist at 3 months in up to 24% of patients without nitrogen gas blowing. Loss of best corrected visual acuity or ghosting is associated with island formation, and may prolong visual rehabilitation after excimer laser PRK.

  18. HSP47 expression in cornea after excimer laser photoablation.

    Science.gov (United States)

    Kasagi, Yasuo; Yamashita, Hidetoshi

    2002-01-01

    The expression of heat shock protein 47 (HSP47) was observed histologically to investigate the spatial and chronological effects of excimer laser photoablation. HSP47 expression after radial keratotomy (RK) was also investigated and compared with the effects after excimer laser photoablation. Twenty-eight male rabbits were used. The rabbits were divided with two groups and treated with either excimer laser photoablation or four radial incisions to simulate corneal refractive surgery. The chronological and spatial changes in the expression of HSP47 were observed immunohistochemically. In eyes that underwent excimer laser photoablation, HSP47 was detected in the basal layer of the epithelial cells and in the superficial stromal layer 3 days after surgery. After 5 and 7 days, HSP47 expression extended to the deep layer of the stroma and to the endothelial cells. After 14 days, HSP47 was detected only in the deep layer of the stroma and in the endothelial cells. After 28 days, HSP47 expression was reduced. In eyes that underwent RK, HSP47 was detected in the basal layer of the epithelial cells and in the stroma surrounding the wound 1 day after surgery. After 3 and 7 days, HSP47 expression did not expand further. After 28 days, HSP47 expression diminished. Excimer laser photoablation affects the whole layer of the cornea, and may be caused by the shock wave that occurs as a result of photoablation. In addition, interaction among the keratocytes may propagate the stress-induced response to the whole layer of the cornea. With RK, the wound is smaller and deeper. HSP47 expression occurs earlier, but is limited to the area surrounding the wound.

  19. Corrosion resistance improvement of metals by excimer laser surface treatment

    Science.gov (United States)

    Autric, Michel L.; Perrais, Jacqueline; Barreau, Gerard

    2000-02-01

    KrF excimer laser has been used for physical and chemical transformations of metallic materials and coated metal samples. Aluminum alloys, steels and chromium coated mild steel have been treated under excimer laser radiation in order to improve their mechanical properties and their corrosion and oxidation resistance. The laser surface treatment leads, after surface remelting process, to important changes in the topography, the microstructure, the phases and the chemical composition of the near-surface region resulting in different hardness, wear properties and corrosion/oxidation behavior. We focus this paper on aluminum alloys (2000 and 6000 type) and steels irradiated using a krypton fluoride laser (20 ns, 0.5 - 10 J/cm2, up to 200 Hz) in laboratory air. The analysis were carried out by means of scanning electron microscopy, energy dispersive spectroscopy, coupled and low incidence angle X-ray diffraction, microhardness tester and electrochemical test equipments.

  20. Excimer laser assisted chemical machining of SiC ceramic

    Science.gov (United States)

    Hibi, Yuko; Enomoto, Yuji; Kikuchi, Kaoru; Shikata, Nobuo; Ogiso, Hisato

    1995-02-01

    A highly effective method of machining ceramic has been newly developed using a krypton fluoride (KrF) excimer laser with a 248 nm wavelength. The laser was irradiated on SiC in water to form a soft hydrous oxide layer by photochemical reaction. The softened layer was then cut with a diamond tool to form a mirror surface finish. The optimum conditions were found for both high machining rate and better surface integrity of SiC.

  1. Impacts of excimer laser annealing on Ge epilayer on Si

    Science.gov (United States)

    Huang, Zhiwei; Mao, Yichen; Yi, Xiaohui; Lin, Guangyang; Li, Cheng; Chen, Songyan; Huang, Wei; Wang, Jianyuan

    2017-02-01

    The impacts of excimer laser annealing on the crystallinity of Ge epilayers on Si substrate grown by low- and high-temperature two-step approach in an ultra-high vacuum chemical vapor deposition system were investigated. The samples were treated by excimer laser annealing (ELA) at various laser power densities with the temperature above the melting point of Ge, while below that of Si, resulting in effective reduction of point defects and dislocations in the Ge layer with smooth surface. The full-width at half-maximum (FWHM) of X-ray diffraction patterns of the low-temperature Ge epilayer decreases with the increase in laser power density, indicating the crystalline improvement and negligible effect of Ge-Si intermixing during ELA processes. The short laser pulse time and large cooling rate cause quick melting and recrystallization of Ge epilayer on Si in the non-thermal equilibrium process, rendering tensile strain in Ge epilayer as calculated quantitatively with thermal mismatch between Si and Ge. The FWHM of X-ray diffraction patterns is significantly reduced for the two-step grown samples after treated by a combination of ELA and conventional furnace thermal annealing, indicating that the crystalline of Ge epilayer is improved more effectively with pre- annealing by excimer laser.

  2. Lead extraction experience with high frequency excimer laser.

    Science.gov (United States)

    Tanawuttiwat, Tanyanan; Gallego, Daniel; Carrillo, Roger G

    2014-09-01

    A higher frequency Excimer laser sheath using an 80-Hz pulse repetitive rate was approved by the Food and Drug Administration in April 2012. We reported our initial clinical experience with a high-frequency Excimer laser sheath and compared it with lower-frequency laser sheaths which have been previously used. In this single center, retrospective cohort study, we evaluated patients who underwent lead extraction from December 2008 to May 2013. Those who underwent lead removal without using a laser sheath or with approaches other than subclavian were excluded. Primary endpoints included total laser time, number of pulses, and complications. Data on clinical characteristics, lead type, indications, and outcomes were prospectively collected and analyzed. A total of 427 patients were included in the study (72.6% male; age 67.9 ± 15.23 years). Lower frequency and higher frequency laser sheaths were used in 315 and 112 patients, respectively. A total of 821 leads were removed with 765 leads (93.2%) extracted using the Excimer laser sheath. Lead age was 5.71 ± 4.96 years. Complete extraction was seen in all patients. A higher-frequency laser sheath was associated with a lower laser time and a lower total number of laser pulses even after adjustments for the number of leads, type of leads, and lead age. In the higher frequency group, mortality rate was 0.9% and minor complication rate was 3.6%. When compared with the lower-frequency laser sheath, the higher-frequency laser sheath requires less laser times and more efficient amount of pulses for lead extraction with comparable success rate. Due to the rarity of major and minor complications, no statistical significance was found between the two groups. ©2014 Wiley Periodicals, Inc.

  3. Reversible Femtosecond Laser-Assisted Myopia Correction: A Non-Human Primate Study of Lenticule Re-Implantation after Refractive Lenticule Extraction: e67058

    National Research Council Canada - National Science Library

    Andri K Riau; Romesh I Angunawela; Shyam S Chaurasia; Wing S Lee; Donald T Tan; Jodhbir S Mehta

    2013-01-01

      LASIK (laser-assisted in situ keratomileusis) is a common laser refractive procedure for myopia and astigmatism, involving permanent removal of anterior corneal stromal tissue by excimer ablation beneath a hinged flap...

  4. Reversible femtosecond laser-assisted myopia correction: a non-human primate study of lenticule re-implantation after refractive lenticule extraction

    National Research Council Canada - National Science Library

    Riau, Andri K; Angunawela, Romesh I; Chaurasia, Shyam S; Lee, Wing S; Tan, Donald T; Mehta, Jodhbir S

    2013-01-01

    LASIK (laser-assisted in situ keratomileusis) is a common laser refractive procedure for myopia and astigmatism, involving permanent removal of anterior corneal stromal tissue by excimer ablation beneath a hinged flap...

  5. Triggering Excimer Lasers by Photoionization from Corona Discharges

    Science.gov (United States)

    Xiong, Zhongmin; Duffey, Thomas; Brown, Daniel; Kushner, Mark

    2009-10-01

    High repetition rate ArF (192 nm) excimer lasers are used for photolithography sources in microelectronics fabrication. In highly attaching gas mixtures, preionization is critical to obtaining stable, reproducible glow discharges. Photoionization from a separate corona discharge is one technique for preionization which triggers the subsequent electron avalanche between the main electrodes. Photoionization triggering of an ArF excimer laser sustained in multi-atmosphere Ne/Ar/F2/Xe gas mixtures has been investigated using a 2-dimensional plasma hydrodynamics model including radiation transport. Continuity equations for charged and neutral species, and Poisson's equation are solved coincident with the electron temperature with transport coefficients obtained from solutions of Boltzmann's equation. Photoionizing radiation is produced by a surface discharge which propagates along a corona-bar located adjacent to the discharge electrodes. The consequences of pulse power waveform, corona bar location, capacitance and gas mixture on uniformity, symmetry and gain of the avalanche discharge will be discussed.

  6. Subjective results of excimer laser correction of myopia. Review

    Directory of Open Access Journals (Sweden)

    V. N. Trubilin

    2012-01-01

    Full Text Available In review presents data of various authors regarding the subjective results excimer laser correction of myopia by LASIK. It was revealed that a group of patients with a high degree of dissatisfaction amounts to 4.6% of the total in all studies. High subjective results are confirmed by the positive dynamics of the «quality of life» of the patient.

  7. Pregnancy-triggered iatrogenic (post-laser in situ keratomileusis) corneal ectasia--a case report.

    Science.gov (United States)

    Padmanabhan, Prema; Radhakrishnan, Aiswaryah; Natarajan, Radhika

    2010-05-01

    To report a patient who developed bilateral corneal ectasia, during pregnancy, one and a half years after laser in situ keratomileusis for correction of myopia. Case report with relevant literature review. A 20-year-old woman, with a stable myopic astigmatism underwent laser in situ keratomileusis for the correction of her refractive error. Preoperative clinical examination and topographic automated keratoconus screening did not suggest keratoconus in either eye. The patient had a preoperative corneal thickness of 527 and 525 microm, and a postoperative residual bed thickness of 305 and 282 microm in the right and left eyes, respectively. After being fully satisfied with the outcome of the procedure, she reported 18 months later, in the first trimester of pregnancy, with signs and symptoms of corneal ectasia, which steadily worsened with advancing pregnancy. Pregnancy could prompt hormonal changes, which in turn could affect the biomechanical stability of the cornea, leading to corneal ectasia.

  8. Effects of laser in situ keratomileusis (LASIK) on corneal biomechanical measurements with the Corvis ST tonometer

    OpenAIRE

    Frings A; Linke SJ; Bauer EL; Druchkiv V; Katz T; Steinberg J

    2015-01-01

    Andreas Frings,1,* Stephan J Linke,1,2,* Eva L Bauer,1 Vasyl Druchkiv,1 Toam Katz,1,2 Johannes Steinberg1,2 1Department of Ophthalmology, University Medical Center Hamburg-Eppendorf (UKE), Hamburg, Germany; 2Care Vision Refractive Center, Hamburg, Germany *These authors contributed equally to this work Purpose: This study was initiated to evaluate biomechanical changes using the Corvis ST tonometer (CST) on the cornea after laser in situ keratomileusis (LASIK). Setting: University Medical...

  9. Laser in situ keratomileusis surgery is not safe for mili-tary personnel

    OpenAIRE

    Jian-he XIAO; Zhang, Mao-Nian; Cai-hui JIANG; Zhang, Ying; QIU Huai-yu

    2012-01-01

    【Abstract】Objective: To investigate the relation-ship between eye injury and laser in-situ keratomileusis (LASIK) surgery in military personnel. Methods: This retrospective study collected the data from 27 evacuation hospitals of Chinese army. All medical records of eye injuries in military personnel admitted to the 27 hospitals between January 2006 and December 2010 were reviewed. Patients’ detailed information was analyzed, in-cluding the injury time, place, type, ca...

  10. Automatic alignment of double optical paths in excimer laser amplifier

    Science.gov (United States)

    Wang, Dahui; Zhao, Xueqing; Hua, Hengqi; Zhang, Yongsheng; Hu, Yun; Yi, Aiping; Zhao, Jun

    2013-05-01

    A kind of beam automatic alignment method used for double paths amplification in the electron pumped excimer laser system is demonstrated. In this way, the beams from the amplifiers can be transferred along the designated direction and accordingly irradiate on the target with high stabilization and accuracy. However, owing to nonexistence of natural alignment references in excimer laser amplifiers, two cross-hairs structure is used to align the beams. Here, one crosshair put into the input beam is regarded as the near-field reference while the other put into output beam is regarded as the far-field reference. The two cross-hairs are transmitted onto Charge Coupled Devices (CCD) by image-relaying structures separately. The errors between intersection points of two cross-talk images and centroid coordinates of actual beam are recorded automatically and sent to closed loop feedback control mechanism. Negative feedback keeps running until preset accuracy is reached. On the basis of above-mentioned design, the alignment optical path is built and the software is compiled, whereafter the experiment of double paths automatic alignment in electron pumped excimer laser amplifier is carried through. Meanwhile, the related influencing factors and the alignment precision are analyzed. Experimental results indicate that the alignment system can achieve the aiming direction of automatic aligning beams in short time. The analysis shows that the accuracy of alignment system is 0.63μrad and the beam maximum restoration error is 13.75μm. Furthermore, the bigger distance between the two cross-hairs, the higher precision of the system is. Therefore, the automatic alignment system has been used in angular multiplexing excimer Main Oscillation Power Amplification (MOPA) system and can satisfy the requirement of beam alignment precision on the whole.

  11. Post-laser in-situ keratomileusis ectasia: current understanding and future directions.

    Science.gov (United States)

    Randleman, J Bradley

    2006-08-01

    The aim of this article is to review the causes, risk factors, management, and future research directions for corneal ectasia after laser in situ keratomileusis. Complex corneal biomechanical processes influence the integrity of the normal and postoperative cornea, and developing an understanding of these processes facilitates recognition of risk factors for ectasia after laser in-situ keratomileusis. Currently identified risk factors include keratoconus, high myopia, low residual stromal bed thickness from excessive ablation or thick flap creation, and defined topographic abnormalities such as forme fruste keratoconus and pellucid marginal corneal degeneration. Ectasia can also rarely occur in patients without currently identifiable risk factors, and future identification of at-risk patients may be facilitated by corneal interferometry and corneal hysteresis measurements. Utilization of intraoperative pachymetry measurements at the time of surgery and confocal microscopy prior to enhancement to measure residual stromal bed thickness should avoid unanticipated low residual stromal bed thickness. Management options for ectasia after laser in situ keratomileusis include intraocular pressure reduction, rigid gas permeable contact lenses, and intracorneal ring segments, in addition to corneal transplantation. In the future, collagen cross-linking may reduce corneal steepening and improve refractive error. When ectasia develops, early recognition and proper management are essential to prevent progression, to promote visual rehabilitation, and to reduce the need for corneal transplantation for these patients.

  12. Histologic, ultrastructural, and immunofluorescent evaluation of human laser-assisted in situ keratomileusis corneal wounds.

    Science.gov (United States)

    Dawson, Daniel G; Kramer, Theresa R; Grossniklaus, Hans E; Waring, George O; Edelhauser, Henry F

    2005-06-01

    To evaluate human corneas after laser-assisted in situ keratomileusis at different postoperative intervals. Thirty-eight postmortem corneas from 20 patients with postoperative intervals from 2 months to 6.5 years after laser-assisted in situ keratomileusis surgery were collected from eye banks. The corneas were trisected and processed for conventional histologic analysis, transmission electron microscopy, and immunofluorescence. Light microscopy and transmission electron microscopy showed focal undulations in Bowman layer, focal epithelial hypertrophic modifications, and a variably thick (range, 0.4-16.4-mum) lamellar stromal interface scar in all specimens. The flap wound margin, which was adjacent to the epithelium, healed by producing an approximately 8-mum-thick hypercellular fibrotic stromal scar, whereas the central and paracentral wound regions healed differently because a thinner (approximately 5-mum) hypocellular primitive stromal scar was present in all the corneas examined. Immunofluorescence identified increased type 3 collagen and myofibroblasts in the hypercellular fibrotic scar regions and decreased or absent levels of all corneal stromal components other than type 1 collagen in the hypocellular primitive scar regions. After laser-assisted in situ keratomileusis surgery, the keratocyte-mediated production of a variably thick lamellar corneal stromal scar occurs, resulting in 2 regional types of scarring. The hypercellular fibrotic scar at the wound margin is usually visible clinically and functions to hold the flap in place, while the more central hypocellular primitive scar is not visible clinically and allows easy lifting of the flap postoperatively.

  13. Penetrating Keratoplasty for Keratoconus – Excimer Versus Femtosecond Laser Trephination

    Science.gov (United States)

    Seitz, Berthold; Langenbucher, Achim; Hager, Tobias; Janunts, Edgar; El-Husseiny, Moatasem; Szentmáry, Nora

    2017-01-01

    Background: In case of keratoconus, rigid gas-permeable contact lenses as the correction method of first choice allow for a good visual acuity for quite some time. In a severe stage of the disease with major cone-shaped protrusion of the cornea, even specially designed keratoconus contact lenses are no more tolerated. In case of existing contraindications for intrastromal ring segments, corneal transplantation typically has a very good prognosis. Methods: In case of advanced keratoconus – especially after corneal hydrops due to rupture of Descemet’s membrane – penetrating keratoplasty (PKP) still is the surgical method of first choice. Noncontact excimer laser trephination seems to be especially beneficial for eyes with iatrogenic keratectasia after LASIK and those with repeat grafts in case of “keratoconus recurrences” due to small grafts with thin host cornea. For donor trephination from the epithelial side, an artificial chamber is used. Wound closure is achieved with a double running cross-stitch suture according to Hoffmann. Graft size is adapted individually depending on corneal size („as large as possible – as small as necessary“). Limbal centration will be preferred intraoperatively due to optical displacement of the pupil. During the last 10 years femtosecond laser trephination has been introduced from the USA as a potentially advantageous approach. Results: Prospective clinical studies have shown that the technique of non-contact excimer laser PKP improves donor and recipient centration, reduces “vertical tilt” and “horizontal torsion” of the graft in the recipient bed, thus resulting in significantly less “all-sutures-out” keratometric astigmatism (2.8 vs. 5.7 D), higher regularity of the topography (SRI 0.80 vs. 0.98) and better visual acuity (0.80 vs. 0.63) in contrast to the motor trephine. The stage of the disease does not influence functional outcome after excimer laser PKP. Refractive outcomes of femtosecond laser

  14. Comparison of DLK incidence after laser in situ keratomileusis associated with two femtosecond lasers: Femto LDV and IntraLase FS60

    Directory of Open Access Journals (Sweden)

    Tomita M

    2013-07-01

    Full Text Available Minoru Tomita,1–3 Yuko Sotoyama,1 Satoshi Yukawa,1 Tadayuki Nakamura1 1Shinagawa LASIK Center, Chiyoda-ku, Tokyo, Japan; 2Department of Ophthalmology, Wenzhou Medical College, Wenzhou, People’s Republic of China; 3Eye Can Cataract Surgery Center, Manila, Philippines Purpose: To compare the incidence of diffuse lamellar keratitis (DLK after laser in situ keratomileusis (LASIK with flap creation using the Femto LDV and IntraLase™ FS60 femtosecond lasers. Methods: A total of 818 consecutive myopic eyes had LASIK performed using either Femto LDV or IntraLase FS60 for flap creation. The same excimer laser, the Allegretto Wave® Eye-Q Laser, was used for correcting refractive errors for all patients. In the preoperative examination, uncorrected distance visual acuity, corrected distance visual acuity, and manifest refraction spherical equivalent were measured. At the postop examination, the same examinations were performed along with a slit-lamp biomicroscopic examination, and patients with DLK were classified into stages. For the statistical analysis of the DLK occurrence rate and the visual and refractive outcomes, the Mann-Whitney’s U-test was used. Results: In the Femto LDV group with 514 eyes, 42 (8.17% had DLK. In the IntraLase FS60 group with 304 eyes, 114 (37.5% had DLK. There was a statistically significant difference in the DLK incidence rate between these groups (P < 0.0001. Both groups had excellent visual and refractive outcomes. Although low levels of DLK were observed for both groups, they did not affect visual acuity. Conclusion: While there were significantly fewer incidences of low level DLK when using Femto LDV, neither femtosecond laser induced high levels of DLK, and any postoperative DLK cleared up within 1 week. Therefore, both lasers provide excellent results, with no clinical differences, and both excel at flap creation for LASIK. Keywords: LASIK, Ziemer, Femto LDV, DLK, IntraLase FS60, femtosecond laser

  15. Levels of interleukin-6 in tears before and after excimer laser treatment.

    Science.gov (United States)

    Resan, Mirko; Stanojević, Ivan; Petković, Aleksandra; Pajić, Bojan; Vojvodić, Danilo

    2015-04-01

    Immune response and consequent inflammatory process which originate on ocular surface after a trauma are mediated by cytokines. Photoablation of corneal stroma performed by excimer laser causes surgically induced trauma. Interleukin-6 (IL-6) is mostly known as a proinflammatory cytokine. However, it also has regenerative and anti-inflammatory effects. It is supposed that this cytokine is likely to play a significant role in the process of corneal wound healing response after photoablation of stroma carried out by laser in situ keratomileusis (LASIK) or photorefractive keratectomy (PRK) methods. The aim of this study was to determine and compare the levels of IL-6 in tears before and after treatment with LASIK and PRK methods. The study included 68 shortsighted eyes up to -3.0 diopter sphere, i.e. 198 samples of tears (per three samples taken from each of the eyes), divided into two groups according to the kind of excimer laser intervention performed: the group 1--eyes treated by LASIK method (n=31), and the group 2--eyes treated by the PRK method (n=37). The samples of tears were taken from each eye at the following time points: before excimer laser treatment (0 h, the control group), 1 h after the treatment (1 h) and 24 h after the treatment (24 h). The patients did not use anti-inflammatory therapy 24 h after the intervention. Tear samples were collected using microsurgical sponge. Level of IL-6 in tear fluid was determined by the flow cytometry method, applying a commercial test kit which allowed cytokine detection from a small sample volume. Results. The values of IL-6 were detectable in 16% of samples before LASIK treatment and in 30% of samples before PRK treatment. One h after the treatment IL-6 was detectable in 29% of samples for the LASIK group and 43% of samples for the PRK group, and 24 h after the treatment it was detectable in 19% of samples for the LASIK group and in 57% of samples for the PRK group. When we analyzed the dynamics of IL76 production

  16. Improved contrast sensitivity and visual acuity after wavefront-guided laser in situ keratomileusis: in-depth statistical analysis.

    Science.gov (United States)

    Tuan, Kuang-mon Ashley; Liang, Junzhong

    2006-02-01

    To evaluate changes in contrast sensitivity and visual acuity following wavefront-guided laser in situ keratomileusis (LASIK) procedures with the Visx CustomVue system. Six clinical sites that participated in an Investigational Device Exemption clinical study. Two hundred seventy-four myopic astigmatic eyes (spherical equivalent range -0.63 to -6.00 diopters) completed 6 months of follow-up examinations. Wavefront-guided procedures using the WaveScan aberrometer and Star S4 excimer laser system with variable spot scanning were performed at 6 clinical locations. Visual acuity and contrast sensitivity under photopic, mesopic, and mesopic-with-glare lighting conditions were tested preoperatively and over a 6-month follow-up period. This study was a retrospective analysis of contrast sensitivity data with controls for the effects of retinal magnification, mesopic pupil size, and the influence of prior soft contact lens wear on visual outcome. Patients experienced statistically significant improvements in contrast sensitivity at all spatial frequencies and under all lighting conditions (Ppatients. There was more improvement at higher (12 cycles per degree [cpd], 18 cpd) than lower (3 cpd) spatial frequencies. No correlation was found between mesopic pupil size and contrast sensitivity. Results stratified by spectacle or soft contact lens wear were similar. Soft contact lens wearers had slightly higher disability glare scores than spectacle wearers. A significant number of patients experienced improved corneal optical quality after wavefront-guided LASIK. The contrast sensitivity in most patients was unchanged. Contrast sensitivity improved in a significant number of patients. There was no correlation between mesopic pupil size and mesopic or mesopic-with-glare contrast performance. Spectacle wearers improved more than soft contact lens wearers.

  17. Scattered UV irradiation during VISX excimer laser keratorefractive surgery.

    Science.gov (United States)

    Hope, R J; Weber, E D; Bower, K S; Pasternak, J P; Sliney, D H

    2008-04-01

    To evaluate the potential occupational health hazards associated with scattered ultraviolet (UV) radiation during photorefractive keratectomy (PRK) using the VISX Star S3 excimer laser. The Laser Vision Center, National Naval Medical Center, Bethesda, Maryland, USA. Intraoperative radiometric measurements were made with the Ophir Power/Energy Meter (LaserStar Model PD-10 with silicon detector) during PRK treatments as well as during required calibration procedures at a distance of 20.3 cm from the left cornea. These measurements were evaluated using a worst-case scenario for exposure, and then compared with the American Conference of Governmental Industrial Hygeinists (ACGIH) Threshold Value Limits (TVL) to perform a risk/hazard analysis. During the PRK procedures, the highest measured value was 248.4 nJ/pulse. During the calibration procedures, the highest measured UV scattered radiation level was 149.6 nJ/pulse. The maximum treatment time was 52 seconds. Using a worst-case scenario in which all treatments used the maximum power and time, the total energy per eye treated was 0.132 mJ/cm2 and the total UV radiation at close range (80 cm from the treated eye) was 0.0085 mJ/cm2. With a workload of 20 patients, the total occupational exposure at 80 cm to actinic UV radiation in an 8-hour period would be 0.425 mJ/cm2. The scattered actinic UV laser radiation from the VISX Star S3 excimer laser did not exceed occupational exposure limits during a busy 8-hour workday, provided that operating room personnel were at least 80 cm from the treated eye. While the use of protective eyewear is always prudent, this study demonstrates that the trace amounts of scattered laser emissions produced by this laser do not pose a serious health risk even without the use of protective eyewear.

  18. Excimer laser cleaning of mud stained paper and parchment

    Directory of Open Access Journals (Sweden)

    Duarte, J. P.

    1998-04-01

    Full Text Available The main advantage of excimer lasers when processing materials, its the emission of a radiation with wavelength in the ultraviolet region. This characteristic allows an extremely accurate and very well defined shape of material removal as well as total absence of heat affected zone and alterations in the material structure. In excimer laser paper and parchment cleaning, the mud is removed by breaking the physicalchemical bonding between this last one and the material to be cleaned not affecting neither its structure nor the chromatic pigment existing in some samples.

    A principal vantagem dos lasers de excímeros, no processamento de materiais, é a emissão de um feixe luminoso com comprimento de onda compreendido na região do ultravioleta, permitindo urna remoçao do material com precisão muito elevada e excelente definição de bordos, ausência de zona térmicamente afectada e ausência de alterações da estrutura. Na limpeza dos papéis e pergaminhos a lama é removida por quebra das ligações fisico-químicas entre a lama e o papel não se afectando a estrutura deste, assim como não se afectaram os pigmentos cromáticos existentes em algumas amostras.

  19. Recent developments on microablation of glass materials using excimer lasers

    Science.gov (United States)

    Tseng, Ampere A.; Chen, Ying-Tung; Chao, Choung-Lii; Ma, Kung-Jeng; Chen, T. P.

    2007-10-01

    For many years, the development of effective laser machining techniques for making glass-based microcomponents and devices has been a critical factor in the birth of new photonic and biomedical microsystems. In this article, the characteristics and abilities of excimer lasers for micromachining of a wide range of glass materials are reviewed and studied. Following the introduction, the special features of excimer lasers are discussed. The typical micromachining system used for glass materials is presented. Then, the fundamental micromachining parameters and the associated morphologies of machined surfaces are evaluated. The approaches by controlling the ablation rate for making the curve surfaces are specifically formulated. Although a wide range of commercially available glasses is covered in this article, two types of the most widely used glasses, borosilicate glass and fused silica, are thoroughly examined to illustrate the complexity in micromachining the glass materials. The procedures to machine single, arrayed, curved microstructures are described. The utilizations of these procedures for making microneedles, optical waveguides, submicron grating, and microlenses are specifically demonstrated. Finally, recommendations for future efforts are presented.

  20. Vitreoretinal surgery with the 193-nm excimer laser

    Science.gov (United States)

    Palanker, Daniel V.; Hemo, Itzhak; Turovets, Igor; Zauberman, Hanan; Lewis, Aaron

    1994-06-01

    The 193-nm excimer laser is known for its ability to precisely ablate soft biological tissues in the air environment with sub- micron depth control and sub-micron damage zones in the surrounding. The lack of a convenient delivery system and strong absorption of this radiation by biological liquids prevented, until recently, microsurgical applications of this laser. We have constructed special tips that are capable of delivering enough energy for effective removal of soft tissues in a strongly absorbing liquid environment. These tips attach to an articulated arm-based delivery system. This instrument was applied to vitreoretinal membranes removal. The accepted technique for these membranes removal is mechanical peeling and cutting which is associated with strong traction of the retina and this occasionally results in retinal damage. It was demonstrated in this study that the 193-nm excimer laser is capable of safely and precisely cutting and ablating these membranes which enable their removal without exerting any tractional forces on the retina. The effective cutting regime of retina and vitreoretinal membranes occurred at energy fluence of about 250- to 350-mJ/cm2/pulse with a corresponding cutting depth of 50 to 150 micrometers /pulse. The results obtained in this study suggest that this technology could be applicable to a wide variety of intraocular procedures.

  1. Femtosecond laser-assisted laser in situ keratomileusis versus photorefractive keratectomy: Effect on ocular surface condition.

    Science.gov (United States)

    Sauvageot, Paola; Julio, Gemma; Alvarez de Toledo, Juan; Charoenrook, Victor; Barraquer, Rafael I

    2017-02-01

    To compare ocular surface characteristics in eyes after femtosecond laser-assisted laser in situ keratomileusis (LASIK) or photorefractive keratectomy (PRK). Centro de Oftalmologia Barraquer, Barcelona, Spain. Prospective comparative observational study. Patients with myopia who had femtosecond laser-assisted LASIK or PRK were included. Tear osmolarity, the Ocular Surface Disease Index questionnaire, Schirmer I, corneal sensitivity, tear breakup time (TBUT), and corneal fluorescein staining were evaluated preoperatively and 3, 6, and 12 months postoperatively. The Wilcoxon signed-rank test was used for temporal intragroup analysis, and the Mann-Whitney U test was used for intergroup comparisons. The study comprised 44 patients (44 eyes) with myopia. Comparison of the parameters between the femtosecond laser-assisted LASIK group (22 eyes) and the PRK group (22 eyes) showed a similar temporal progression postoperatively. Compared with the preoperative evaluation, corneal sensitivity decreased after 3 months (P = .002 and P = .02, respectively) and 6 months (P = .03 and P = .04, respectively). The TBUT reached the highest mean value after 12 months (P = .01 and P = .04, respectively), and tear osmolarity was slightly increased after 1 year, although the mean values remained within the normal range (P = .01 and P = .04, respectively). The only difference between the 2 groups was lower corneal sensitivity in the femtosecond laser-assisted LASIK group after 3 months (P = .02). The ocular surface condition could be considered clinically unaltered after 1 year in both groups. Femtosecond laser-assisted LASIK and PRK techniques seemed to be safe for the ocular surface condition and to have a similar effect on it. Copyright © 2017 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  2. Comparison of corneal aberration changes after laser in situ keratomileusis performed with mechanical microkeratome and IntraLase femtosecond laser: 1-year follow-up.

    Science.gov (United States)

    Buzzonetti, Luca; Petrocelli, Gianni; Valente, Paola; Tamburrelli, Ciro; Mosca, Luigi; Laborante, Antonio; Balestrazzi, Emilio

    2008-02-01

    To compare corneal aberration changes 1 year after myopic laser in situ keratomileusis (LASIK) performed with a mechanical microkeratome and IntraLase femtosecond laser. Twenty four eyes of 15 patients underwent LASIK with the Hansatome microkeratome, and 23 eyes of 13 patients underwent LASIK with the IntraLase femtosecond laser. A standard ablation was performed with the Bausch & Lomb Technolas 217 excimer laser. Topography data were used to calculate corneal aberrations with a 3.0 mm and 5.00 mm pupil, before and 12 months after surgery. The increasing factor (IF), defined as the ratio between the postoperative and preoperative mean value of the optical aberration, was calculated. The method of Mulhern et al was used to evaluate the centration of ablation. The comalike aberration was correlated with the decentration of ablation. The Student t test was used for the statistical anaylsis. The postoperative mean decentration of ablation was <0.5 mm. The comalike aberration appeared to be positively correlated with the decentration of ablation in both groups with a 5.0-mm pupil (P < 0.05). With a 3.00-mm pupil, the comalike aberration changed in the Hansatome group, whereas with a 5.00-mm pupil, all aberrations statistically significantly changed in both groups (P < 0.05). The IF similarly increased in 2 groups for spherical-like aberration, whereas IF greatly increased for total and comalike aberrations in the Hansatome group. Wavefront corneal aberrations change significantly 1 year after myopic LASIK performed with the Hansatome microkeratome as well as with IntraLase femtosecond lasers. Both of the procedures induce higher-order aberrations in the anterior corneal surface, but the amount of comalike aberration increases more with the Hansatome mechanical microkeratome.

  3. Long-term safety and efficacy follow-up of prophylactic higher fluence collagen cross-linking in high myopic laser-assisted in situ keratomileusis

    Directory of Open Access Journals (Sweden)

    Kanellopoulos AJ

    2012-07-01

    Full Text Available Anastasios John KanellopoulosLaservision.gr Institute, Athens, Greece, and New York University Medical School, New York, NY, USABackground: The purpose of this study was to evaluate the safety and efficacy of ultraviolet A irradiation cross-linking on completion for cases of high myopic laser-assisted in situ keratomileusis (LASIK.Methods: Forty-three consecutive LASIK cases treated with femtosecond laser flap and the WaveLight excimer platform were evaluated perioperatively for uncorrected visual acuity, best corrected spectacle visual acuity, refraction, keratometry, topography, total and flap pachymetry, corneal optical coherence tomography, and endothelial cell count. All eyes at the completion of LASIK had cross-linking through the repositioned flap, with higher fluence (10 mW/cm2 ultraviolet light of an average 370 µm wavelength and 10 mW/cm2 fluence applied for 3 minutes following an earlier single instillation of 0.1% riboflavin within the flap interface. Mean follow-up duration was 3.5 (range 1.0–4.5 years.Results: Mean uncorrected visual acuity changed from 0.2 to 1.2, best corrected spectacle visual acuity from 1.1 to 1.2, spherical equivalent from -7.5 diopters (D to -0.2 D, keratometry from 44.5 D to 38 D, flap pachymetry from 105 µm to, total pachymetry from 525 to 405, and endothelial cell count from 2750 to 2800. None of the cases developed signs of ectasia or significant regression during follow-up.Conclusion: Prophylactic collagen cross-linking for high-risk LASIK cases appears to be a safe and effective adjunctive treatment for refractive regression and potential ectasia. This application may be viewed as prophylactic customization of the biomechanical behavior of corneal collagen.Keywords: prophylactic collagen cross-linking, laser-assisted in situ keratomileusis, high-risk, post-LASIK ectasia

  4. Laser drilling of metals with a XeCl excimer laser

    NARCIS (Netherlands)

    Schoonderbeek, A.

    2005-01-01

    This thesis is about laser drilling with a unique excimer laser with a nearly diffraction-limited beam and relatively long optical pulse duration of 175 ns. The combination of high processing speed and high processing quality suitable for industrial applications can be obtained because the excellent

  5. Intraoperative and Postoperative Complications of Laser in situ Keratomileusis Flap Creation Using IntraLase Femtosecond Laser and Mechanical Microkeratomes

    OpenAIRE

    Espandar, Ladan; Meyer, Jay

    2010-01-01

    An essential step of laser in situ keratomileusis surgery is corneal flap creation, Femtosecond (FS)-assisted or mechanical microkeratome. Each type has rare intraoperative and postoperative complication rates. Several recent studies have identified risk factors and guidelines to help manage these complications. Fortunately, studies have shown no loss of best-corrected visual acuity (BCVA) after the management of intraoperative and postoperative complications in IntraLase FS and mechanical mi...

  6. Corneal endothelial cell changes 5 years after laser in situ keratomileusis: femtosecond laser versus mechanical microkeratome.

    Science.gov (United States)

    Klingler, Kyle N; McLaren, Jay W; Bourne, William M; Patel, Sanjay V

    2012-12-01

    To compare corneal endothelial cell density (ECD) and morphology between flap creation with a femtosecond laser and flap creation with a mechanical microkeratome 5 years after laser in situ keratomileusis (LASIK). Mayo Clinic, Rochester, Minnesota, USA. Prospective randomized masked paired-eye study. In this study of LASIK for myopia or myopic astigmatism, fellow eyes were randomized by ocular dominance to flap creation by a femtosecond laser or by a mechanical microkeratome. Central endothelial images were analyzed before and 3 years and 5 years after LASIK; endothelial cell variables were compared between treatments at each examination. Relationships between endothelial cell loss and contact lens wear, residual bed thickness, and preoperative refractive error were evaluated. There were no differences in the ECD, percentage of hexagonal cells, or coefficient of variation of cell area between treatments at any examination (all P = .99); the smallest detectable differences were 120 cells/mm(2), 5%, and 2%, respectively. The mean annual rate of corneal endothelial cell loss was -0.1% ± 1.2% (SD) and -0.1% ± 1.0% for the femtosecond laser and the mechanical microkeratome, respectively. Endothelial cell loss was not associated with contact lens wear, residual bed thickness, or preoperative refractive error. The energy delivered to the cornea during femtosecond laser flap creation did not affect the corneal endothelium 5 years after LASIK when compared with flap creation with a mechanical microkeratome. Corneas that have had either method of flap creation could be accepted as donor tissue for endothelial keratoplasty from the standpoint of endothelial health. No author has a financial or proprietary interest in any material or method mentioned. Copyright © 2012 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  7. Scattered ultraviolet emissions during refractive surgery using a high-frequency, wavefront-optimized excimer laser platform.

    Science.gov (United States)

    Bower, Kraig S; Edwards, Jayson D; Ryan, Denise Sediq; Coe, Charles D; Hope, Robert J; Sliney, David H

    2010-08-01

    To evaluate occupational ultraviolet (UV) exposure during photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) with the Allegretto Wave Eye-Q 400 Hz excimer laser. Walter Reed Center for Refractive Surgery, Washington, DC, USA. Intraoperative UV measurements were performed during PRK with epithelial removal using an Amoils brush, PRK with epithelial removal using 20% ethanol, or femtosecond LASIK. A LaserStar power/energy meter with a silicone detector (model PD-10) was used for the measurements. The maximum pulse energy 25.4 cm from the corneal surface was recorded for each surgical procedure. Measurements were evaluated using a worst-case scenario for exposure of operating room personnel, and the results were compared with the occupational exposure limit set by the International Commission on Non-Ionizing Radiation Protection. Measurements were taken during 15 cases of each procedure. The mean maximum exposure was 129.38 nJ/pulse +/- 79.48 (SD) during brush PRK, 69.72 +/- 68.80 nJ/pulse during ethanol PRK, and 29.17 +/- 13.82 nJ/pulse during LASIK. The mean maximum exposure per eye was 0.085 mJ/cm(2), 0.046 mJ/cm(2), and 0.01 mJ/cm(2), respectively. The worst-case cumulative exposure during a heavy workday of 20 patients (40 eyes) was calculated at 3.92 mJ/cm(2), 1.51 mJ/cm(2), and 0.79 mJ/cm(2) for brush PRK, ethanol PRK, and LASIK, respectively. Results indicate that the excimer laser platform used in the study may yield greater UV exposure than previous systems; however, the levels did not exceed occupational exposure limits. No author has a financial or proprietary interest in any material or method mentioned. Published by Elsevier Inc.

  8. EXCIMER-LASER ABLATION OF SOFT-TISSUE - A STUDY OF THE CONTENT OF RAPIDLY EXPANDING AND COLLAPSING BUBBLES

    NARCIS (Netherlands)

    van Leeuwen, T. G.; Jansen, E. D.; Motamedi, M.; Welch, A. J.; Borst, C.

    1994-01-01

    Both holmium (lambda = 2.09 mum) and excimer (lambda = 308 nm) lasers are used for ablation of tissue. In a previous study, excimer laser ablation of aorta produced rapidly expanding and collapsing vapor bubbles. To investigate whether the excimer-induced bubble is caused by vaporization of (tissue)

  9. Femtosecond laser vs mechanical microkeratome for hyperopic laser in situ keratomileusis.

    Science.gov (United States)

    Gil-Cazorla, Raquel; Teus, Miguel A; de Benito-Llopis, Laura; Mikropoulos, Dimitrios G

    2011-07-01

    To compare the outcomes of laser in situ keratomileusis (LASIK) performed with a femtosecond laser vs a mechanical microkeratome for the correction of low to moderate hyperopia. Retrospective, nonrandomized, interventional, comparative case series. settings: Vissum Santa Hortensia, Madrid, Spain.study population and procedures: Patients who had undergone LASIK to correct their hyperopia using the 60-kHz IntraLase femtosecond laser were compared to age- and refraction-matched patients in whom the Moria M2 microkeratome was used. Visual and refractive results 3 months postoperatively were compared between both groups. A total of 144 eyes were analyzed (72 in each group). Mean preoperative sphere was +3.45 ± 1.0 diopters (D) in the IntraLase group vs +3.18 ± 1.3 D in the M2 group (P = .1). Results 3 months postoperatively were: mean residual sphere, +0.44 ± 0.6D vs +0.72 ± 0.8 D (P = .02), respectively; uncorrected visual acuity (UCVA), 0.89 ± 0.2 vs 0.80 ± 0.2 (P = .04); best spectacle-corrected visual acuity (BSCVA), 0.96 ± 0.2 vs 0.92 ± 0.2 (P = .2); safety index, 0.97 ± 0.1 vs 0.98 ± 0.1 (P = .5); efficacy index, 0.89 ± 0.2 vs 0.84 ± 0.2 (P = .3). Hyperopic LASIK performed with the IntraLase femtosecond laser seems to achieve better refractive results 3 months after the surgery compared to the M2 microkeratome, without significant differences in safety between both procedures. Copyright © 2011 Elsevier Inc. All rights reserved.

  10. Low threshold buried-heterostructure quantum well lasers by excimer laser assisted disordering

    Energy Technology Data Exchange (ETDEWEB)

    Epler, J.E.; Thornton, R.L.; Mosby, W.J.; Paoli, T.L.

    1988-10-17

    Laser assisted disordering based upon a direct-write Ar/sup +/ laser beam has been established as a fabrication technique for high quality optoelectronic devices. In this letter, we report a new form of laser assisted disordering in which an excimer laser beam, photolithographically patterned, is used to define the incorporation of Si impurity into GaAs-AlGaAs heterostructure crystals. During a subsequent thermal anneal the diffusing Si induces layer disordering to a depth of approx.1 ..mu..m. The excimer laser assisted disordering process is characterized as a function of the energy density of the laser beam. Also, this technique is used to fabricate high quality buried-heterostructure lasers. With a reflective rear facet, the typical cw threshold current is 4 mA and the maximum power output is 27 mW. The devices exhibit single fundamental mode operation with subsidiary longitudinal side modes suppressed by 34 dB.

  11. Combination treatment with excimer laser and narrowband UVB light in vitiligo patients.

    Science.gov (United States)

    Shin, Sungsik; Hann, Seung-Kyung; Oh, Sang Ho

    2016-01-01

    For the treatment of vitiligo, narrowband UVB (NBUVB) light is considered the most effective for nonsegmental vitiligo, while excimer laser treatment is commonly used for localized vitiligo. However, treatment areas may potentially be missed with excimer laser treatment. We aimed to evaluate the effect of combinational treatment with NBUVB light and excimer laser on vitiligo. All patients were first treated with NBUVB; excimer laser was then applied in conjunction with NBUVB phototherapy due to a slow response or no further improvement with continuous NBUVB treatment alone. To minimize adverse effects, a fixed dose of NBUVB was administered, and the dose of excimer laser was increased based on patient response. Among 80 patients, 54 patients showed responses after combination with excimer laser; however, 26 patients (32.5%) showed no remarkable change after combination therapy. Of the 26 patients who showed no further response, 12 patients (46.1%) presented with vitiligo on the acral areas, which are known to the least responsive sites. Our study suggests that combined treatment of NBUVB and excimer laser in vitiligo may enhance the treatment response without remarkable side effects, therefore might also increase the compliance of the patients to the treatment. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  12. Laser in situ keratomileusis surgery is not safe for mili-tary personnel

    Directory of Open Access Journals (Sweden)

    XIAO Jian-he

    2012-04-01

    Full Text Available 【Abstract】Objective: To investigate the relation-ship between eye injury and laser in-situ keratomileusis (LASIK surgery in military personnel. Methods: This retrospective study collected the data from 27 evacuation hospitals of Chinese army. All medical records of eye injuries in military personnel admitted to the 27 hospitals between January 2006 and December 2010 were reviewed. Patients’ detailed information was analyzed, in-cluding the injury time, place, type, cause, as well as examination, treatment and outcome. Results: There were 72 eye-injured patients who had been treated by LASIK before. The incidence was rising year by year. Among them, 69 patients were diagnosed with mechanical ocular injury and 3 with non-mechanical ocular injury; 29 patients had traumatic flap-related complications and 21 patients need surgery. There was statistical differ-ence when compared with those having no refractive sur-gery history. Visual acuity recovered well at discharge. Conclusion: There is a high risk of potential traumatic flap problems after LASIK and it is not recommended in army service. Key words: Eye injuries; Military personnel; Keratomileusis, laser in situ

  13. Corneal biomechanical properties after laser-assisted in situ keratomileusis and photorefractive keratectomy

    Directory of Open Access Journals (Sweden)

    Hwang ES

    2017-10-01

    Full Text Available Eileen S Hwang,1 Brian C Stagg,1 Russell Swan,1 Carlton R Fenzl,1 Molly McFadden,2 Valliammai Muthappan,1 Luis Santiago-Caban,1 Mark D Mifflin,1 Majid Moshirfar1,3 1Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center, 2Department of Internal Medicine, University of Utah, Salt Lake City, 3HDR Research Center, Hoopes Vision, Draper, UT, USA Background: The purpose of this study was to evaluate the effects of laser-assisted in situ keratomileusis (LASIK and photorefractive keratectomy (PRK on corneal biomechanical properties.Methods: We used the ocular response analyzer to measure corneal hysteresis (CH and corneal resistance factor (CRF before and after refractive surgery.Results: In all, 230 eyes underwent LASIK and 115 eyes underwent PRK without mitomycin C (MMC. Both procedures decreased CH and CRF from baseline. When MMC was used after PRK in 20 eyes, it resulted in lower corneal biomechanical properties at 3 months when compared to the other procedures, but all three procedures had similar values at 12 months.Conclusion: Significant but similar decreases in corneal biomechanical properties after LASIK, PRK without MMC, and PRK with MMC were noted. Keywords: corneal biomechanics, photorefractive keratectomy, laser-assisted in situ keratomileusis, corneal hysteresis, corneal resistance factor, mitomycin C

  14. Excimer laser ablation of polyimide: a 14-year IBM perspective

    Science.gov (United States)

    Brannon, James H.; Wassick, Thomas A.

    1997-05-01

    IBM introduced the first commercial high-end mainframe computer system incorporating laser ablation technology in 1991. This milestone was the culmination of nearly a decade of scientific, engineering, and manufacturing effort. Extensive research and development on 308 nm laser ablation of polyimide lead to the first IBM prototype ablation tool in 1987 for the production of via-holes in thin film packaging structures. This prototype, similar to step and repeat photolithography systems, evolved into full-scale manufacturing tools which utilize sophisticated beam shaping, beam homogenizing, and projection optics. But the maturity of this technology belies the fact that the scientific understanding of the laser ablation process is still far from complete. This paper briefly reviews the engineering and scientific accomplishments, both within and external to IBM, that lead to the commercial utilization of the laser ablation process. Current technical tissues are discussed, in addition to alternative IBM applications of polyimide ablation. The paper concludes by discussing the relative merits of excimer vs. solid-state lasers, and how each may impact future manufacturing technology.

  15. Excimer laser surface ablation: a review of recent literature

    National Research Council Canada - National Science Library

    O'Brart, David PS

    2014-01-01

    ...‐epithelial keratomileusis ( LASEK ), microkeratome‐assisted PRK (epi‐ LASIK ) and trans‐epithelial (laser‐assisted) PRK , to help elucidate where and how surface ablation may best fit into current refractive surgical practice...

  16. Study on the excimer laser annealed amorphous hydrogenated silicon carbon films deposited by PECVD

    Energy Technology Data Exchange (ETDEWEB)

    Ambrosone, G. [CNR-INFM CRS-Coherentia, Complesso Universitario MSA, Napoli (Italy); Dipartimento di Scienze Fisiche, Universita di Napoli ' Federico II' , Complesso Universitario MSA, Napoli (Italy); Basa, D.K. [Utkal University, Bhubaneswar (India); Coscia, U. [Dipartimento di Scienze Fisiche, Universita di Napoli ' Federico II' , Complesso Universitario MSA, Napoli (Italy); CNISM Unita' di Napoli, Complesso Universitario MSA, Napoli (Italy); Tresso, E.; Celasco, E. [Dipartimento di Scienza dei Materiali ed Ingegneria Chimica, Politecnico di Torino (Italy); Chiodoni, A. [Materials and Microsystems Laboratory, chi-LAB, Politecnico di Torino (Italy); Pinto, N.; Murri, R. [Dipartimento di Fisica, Universita' di Camerino (Italy)

    2010-04-15

    Hydrogenated amorphous silicon carbon films of different carbon content were deposited by plasma enhanced chemical vapour deposition at low substrate temperature (200 C) and were subjected to excimer laser annealing. X-ray diffraction spectra and field emission scanning electron microscopy images demonstrate that carbon content plays an important role in facilitating the crystallization process induced by the excimer laser treatment (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  17. Shadowgraphic imaging of metal drilling with a long pulse excimer laser

    NARCIS (Netherlands)

    Schoonderbeek, A.; Biesheuvel, C.A.; Hofstra, R.M.; Boller, Klaus J.; Meijer, J.; Miyamoto, Isamu; Ostendorf, Andreas; Sugioka, Koji; Helvajian, Henry

    2003-01-01

    A shadowgraphic imaging technique is used for studying the interaction between the laser beam and the material during laser drilling. The used laser is a XeCl excimer laser with a nearly diffraction limited beam and 175 ns pulse length. We studied how and when the material is removed. Holes are

  18. Contact lens fitting post-laser-in situ keratomileusis (LASIK).

    Science.gov (United States)

    Steele, Chris; Davidson, John

    2007-05-01

    Despite recent advances in refractive surgical procedures a small proportion of patients still achieve sub-optimal results for a variety of reasons. In such cases, contact lenses may provide the only option for visual rehabilitation and restoration of binocular vision post-refractive surgery. The indications for contact lenses post-LASIK may be one, or a combination of the following: *Initial bandage lens for corneal protection. *Residual ametropia--over and under correction. *Irregular astigmatism. * Anisometropia. * Decentred ablation zones. In low powered corrections conventional soft lenses can be fitted in the normal way, giving good levels of acuity. Where there is astigmatism (>0.75 DC) then toric soft contact lenses may appropriate. Rigid lenses may prove to be the only viable option in a number of cases where visual correction is required post-refractive surgery, or in the presence of high levels of astigmatism. Fitting can be more complex however, since a conventional rigid lens cannot follow the shape of both the flattened central cornea and the relatively steeper periphery in higher corrections, as the amount of laser ablation increases. Reverse geometry lenses are indicated where there is a significant difference between the flat central ablated zone and the relatively steeper peripheral cornea. On rare occasions scleral lenses may also be indicated.

  19. Single application on iris localization technology in excimer laser for astigmatism

    Directory of Open Access Journals (Sweden)

    Jun-Hua Hao

    2014-06-01

    Full Text Available AIM:To discuss the single application on iris localization technology in excimer laser for the treatment of astigmatism. METHODS:Totally 203 cases(406 eyesof laser in situ keratomileusis(LASIKin the treatment of compound myopic astigmatism patients were operated from November 2011 to November 2012 in our hospital. They were divided into two groups. One was observation group using iris localization and the other was control group using routine operation. Patients in the observation group of 100 cases(200 eyes, aged 18-43 years old, spherical diopter was -1.25 to -8.75D, astigmatism was -1.0 to -3.25D. In control group, 103 patients(206 eyes, aged 19-44 years old, spherical diopter was -1.75-9.50D, astigmatism was -1.0 to -3.25D. The patients in the observation group before the application of WaveScan aberrometer check for iris image, spherical lens, cylindrical lens and astigmatism axis data operation, only single application of iris location, without using wavefront aberration guided technology, laser cutting patterns for conventional LASIK model, spherical, cylindrical mirror and astigmatism axis data source to preoperative wavefront aberration results. The control group received routine LASIK. It was applicated comprehensive optometry optometry respectively to examine astigmatism and axial, based on the computer analysis during the preoperative, 1wk after the operation, and 6mo. Analysis of using SPSS 17 statistical software, it was independent-sample t test between the two groups of residual astigmatism and astigmatism axis. RESULTS:Postoperative residual astigmatism, the observation group was significantly better than the control group. Astigmatism axial measurement after operation, the observation group was significantly less than that of the control group. Postoperative visual acuity at 6mo, the observation group was better than that of the control group. The difference was statistically significant. CONCLUSION: For patients who cannot

  20. Laser in situ keratomileusis in patients with collagen vascular disease: a review of the literature.

    Science.gov (United States)

    Simpson, Rachel G; Moshirfar, Majid; Edmonds, Jason N; Christiansen, Steven M; Behunin, Nicholas

    2012-01-01

    To evaluate the current United States Food and Drug Administration (FDA) recommendations regarding laser in situ keratomileusis (LASIK) surgery in patients with collagen vascular diseases (CVD) and assess whether these patients make appropriate candidates for laser vision correction, and offer treatment recommendations based on identified clinical data. A literature search was conducted using PubMed, Medline, and Ovid to identify all existing studies of LASIK in patients with collagen vascular diseases. The search was conducted without date limitations. Keywords used for the search included MeSH terms: laser in situ keratomileusis, LASIK, refractive surgery, ocular surgery, and cataract surgery connected by "and" with the following MeSH and natural-language terms: collagen vascular disease, rheumatic disease, systemic disease, rheumatoid arthritis, systemic lupus erythematosus, Sjögren's syndrome, seronegative spondyloarthropathy, HLA B27, ankylosing spondylitis, reactive arthritis, psoriatic arthritis. The abstracts for all studies meeting initial search criteria were reviewed; relevant studies were included. No prospective studies were found; however, four retrospective case studies were identified that examined LASIK surgery in patients with CVD. Several case reports were also identified in similar fashion. The FDA considers CVD a relative contraindication to LASIK surgery, due largely to the ocular complications associated with disease in the CVD spectrum. However, recent studies of LASIK in patients with CVD indicate LASIK may be safe for patients with very well-controlled systemic disease, minimal ocular manifestations, and no clinical signs or history of dry-eye symptoms. LASIK surgery may be safe in patients with rheumatoid arthritis or systemic lupus erythematosus and the seronegative spondyloarthropathies if stringent preoperative criteria are met. Evidence suggests patients with Sjögren's syndrome are not suitable candidates for LASIK.

  1. Advanced excimer laser technologies enable green semiconductor manufacturing

    Science.gov (United States)

    Fukuda, Hitomi; Yoo, Youngsun; Minegishi, Yuji; Hisanaga, Naoto; Enami, Tatsuo

    2014-03-01

    "Green" has fast become an important and pervasive topic throughout many industries worldwide. Many companies, especially in the manufacturing industries, have taken steps to integrate green initiatives into their high-level corporate strategies. Governments have also been active in implementing various initiatives designed to increase corporate responsibility and accountability towards environmental issues. In the semiconductor manufacturing industry, there are growing concerns over future environmental impact as enormous fabs expand and new generation of equipments become larger and more powerful. To address these concerns, Gigaphoton has implemented various green initiatives for many years under the EcoPhoton™ program. The objective of this program is to drive innovations in technology and services that enable manufacturers to significantly reduce both the financial and environmental "green cost" of laser operations in high-volume manufacturing environment (HVM) - primarily focusing on electricity, gas and heat management costs. One example of such innovation is Gigaphoton's Injection-Lock system, which reduces electricity and gas utilization costs of the laser by up to 50%. Furthermore, to support the industry's transition from 300mm to the next generation 450mm wafers, technologies are being developed to create lasers that offer double the output power from 60W to 120W, but reducing electricity and gas consumption by another 50%. This means that the efficiency of lasers can be improve by up to 4 times in 450mm wafer production environments. Other future innovations include the introduction of totally Heliumfree Excimer lasers that utilize Nitrogen gas as its replacement for optical module purging. This paper discusses these and other innovations by Gigaphoton to enable green manufacturing.

  2. Intraoperative and Postoperative Complications of Laser in situ Keratomileusis Flap Creation Using IntraLase Femtosecond Laser and Mechanical Microkeratomes.

    Science.gov (United States)

    Espandar, Ladan; Meyer, Jay

    2010-01-01

    An essential step of laser in situ keratomileusis surgery is corneal flap creation, Femtosecond (FS)-assisted or mechanical microkeratome. Each type has rare intraoperative and postoperative complication rates. Several recent studies have identified risk factors and guidelines to help manage these complications. Fortunately, studies have shown no loss of best-corrected visual acuity (BCVA) after the management of intraoperative and postoperative complications in IntraLase FS and mechanical microkeratome. Refractive surgeons need to be aware of the types of complications that can occur, how to avoid them and how to manage them to ensure the best possible outcomes.

  3. Visual quality after epipolis laser in situ keratomileusis surgery in mild and moderate myopia

    Directory of Open Access Journals (Sweden)

    Yin-Liang Huang

    2015-07-01

    Full Text Available AIM: To comprehensively evaluate of visual quality after epipolis laser in situ keratomileusis(EPI-LASIKin mild to moderate myopia.METHODS: Sixty cases(120 eyesundergone EPI-LASIK with equivalent diopter(SEwere divided into two groups: mild myopia group(60 eyesand moderate myopia group(60 eyes. Objective visual acuity, aberration, contrast sensitivity and glare sensitivity were measured before and 1wk; 1, 6mo after operation, and made comparative analysis. RESULTS: Postoperative uncorrected visual acuity(UCVAof two groups were better than that of preoperative(PPPPPPPCONCLUSION: Visual quality is poorer in mild myopia patients than that in moderate myopia at early stage after EPI-LASIK. Better visual quality is observed at mid-late stage.

  4. The Incidence of Central Serous Chorioretinopathy after Photorefractive Keratectomy and Laser In Situ Keratomileusis

    Science.gov (United States)

    Moshirfar, Majid; Hsu, Maylon; Schulman, Julia; Armenia, Joseph; Sikder, Shameema; Hartnett, M. Elizabeth

    2012-01-01

    Purpose. To assess the incidence of central serous chorioretinopathy (CSCR) following laser in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK). Methods. A chart review was performed to identify all patients with CSCR and a previous history of LASIK or PRK. Results. Over the 6-year study period, 1 of 4,876 eyes which had LASIK or PRK at the Moran Eye Center was diagnosed with CSCR. One other patient was referred from an outside center, developed CSCR symptoms one month after PRK. Both patients were managed conservatively with a final visual acuity of 20/20 or better. All other patients presented 4 or more years after refractive surgery. Conclusions. We report the first 2 CSCR cases developing within one month after PRK. The low incidence argues against a causal association. Topical corticosteroids or anxiety may elevate cortisol levels presenting therapeutic challenges for the management of CSCR after PRK or LASIK. PMID:22518278

  5. Bilateral Iris Atrophy after the Femtosecond Assisted Laser In Situ Keratomileusis Surgery

    Directory of Open Access Journals (Sweden)

    Kenan Olcay

    2015-01-01

    Full Text Available Purpose. To report an unknown complication of laser in situ keratomileusis (LASIK surgery. Case Presentation. A 28-year-old female presented with photophobia and glare to our eye service. She stated in her medical history that she had undergone femtosecond assisted LASIK surgery in both eyes 15 months ago and her symptoms started just after this surgery. On admission, her best-corrected visual acuity was 10/10 in both eyes. She had mydriatic pupils with no direct light reflex. Examination of the anterior segment revealed bilateral iris atrophy projecting within the LASIK ablation zone and a transillumination defect was remarkable on the slit lamp examination. Conclusion. We hypothesized that this condition may have been caused by the abnormally increased IOP that resulted in ischemia in the iris vascular plexus during the suction process of surgery.

  6. Microencapsulation of silicon cavities using a pulsed excimer laser

    KAUST Repository

    Sedky, Sherif M.

    2012-06-07

    This work presents a novel low thermal-budget technique for sealing micromachined cavities in silicon. Cavities are sealed without deposition, similar to the silicon surface-migration sealing process. In contrast to the 1100°C furnace anneal required for the migration process, the proposed technique uses short excimer laser pulses (24ns), focused onto an area of 23mm 2, to locally heat the top few microns of the substrate, while the bulk substrate remains near ambient temperature. The treatment can be applied to selected regions of the substrate, without the need for special surface treatments or a controlled environment. This work investigates the effect of varying the laser pulse energy from 400 mJ cm 2to 800 mJ cm 2, the pulse rate from 1Hz to 50Hz and the pulse count from 200 to 3000 pulses on sealing microfabricated cavities in silicon. An analytical model for the effect of holes on the surface temperature distribution is derived, which shows that much higher temperatures can be achieved by increasing the hole density. A mechanism for sealing the cavities is proposed, which indicates how complete sealing is feasible. © 2012 IOP Publishing Ltd.

  7. Corneal ectasia after myopic laser in situ keratomileusis: a long-term study

    Directory of Open Access Journals (Sweden)

    Spadea L

    2012-11-01

    Full Text Available Leopoldo Spadea,1 Emilia Cantera,2 Magdalena Cortes,2 Nicole Evangelista Conocchia,1 Charles WM Stewart11University of L’Aquila, Department of Biotechnological and Applied Clinical Sciences, Eye Clinic, L’Aquila, 2Villa Stuart Clinic, Department of Ophthalmic Sciences, Rome, ItalyBackground: The purpose of this study was to evaluate the long-term postoperative incidence of and key factors in the genesis of corneal ectasia after myopic laser-assisted in situ keratomileusis (LASIK in a large number of cases.Methods: A retrospective review of one surgeon's myopic LASIK database was performed. Patients were stratified into two groups based on date of surgery, ie, group 1 (1313 eyes from 1999 to 2001 and group 2 (2714 eyes from 2001 to 2003. Visual acuity, refraction, pachymetry, and corneal topography data were available for each patient from examinations performed both before and after the refractive procedures.Results: Of the 4027 surgically treated eyes, 23 (0.57% developed keratectasia during the follow-up period, which was a minimum seven years; nine eyes (0.69% were from group 1 and 14 eyes (0.51% were from group 2. The onset of corneal ectasia was at 2.57 ± 1.04 (range 1–4 years and 2.64 ± 1.29 (range 0.5–5 years, respectively, for groups 1 and 2. The most important preoperative risk factors using the Randleman Ectasia Risk Score System were manifest refractive spherical error in group 1 and a thin residual stromal bed in group 2. Each of the cases that developed corneal ectasia had risk factors that were identified.Conclusion: Ectasia was an uncommon outcome after an otherwise uncomplicated laser in situ keratomileusis procedure. The variables present in eyes developing postoperative LASIK ectasia can be better understood using the Randleman Ectasia Risk Score System.Keywords: corneal topography, Ectasia Risk Score System, keratectasia, myopia, LASIK

  8. Rainbow glare after laser-assisted in situ keratomileusis: a review of literature

    Directory of Open Access Journals (Sweden)

    Moshirfar M

    2016-11-01

    Full Text Available Majid Moshirfar,1,2 Jordan D Desautels,3 Tyler S Quist,4 David F Skanchy,5 Mark T Williams,6 Ryan T Wallace7 1Department of Ophthalmology and Visual Sciences, John A Moran Eye Center, University of Utah School of Medicine, Salt Lake City, UT, 2HDR Research Center, Hoopes Vision, Draper, UT, 3Tufts University School of Medicine, Boston, MA, 4University of Utah School of Medicine, Salt Lake City, UT, 5McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, TX, 6University of California, San Francisco School of Medicine, San Francisco, CA, 7Brigham Young University, Provo, UT, USA Abstract: This article reviews the current literature pertaining to rainbow glare (RG, including incidence rate, clinical presentation, etiology, prognosis, and management. RG is a rare optical complication of femtosecond laser-assisted in situ keratomileusis that results in patients seeing an array of spectral bands surrounding point sources of light under mesopic and scotopic conditions. The mechanism is thought to be a consequence of the formation of a transmissive diffraction grating on the posterior surface of the corneal flap created by the FS laser. RG has a good prognosis and is usually self-limiting. Persistent RG with concomitant residual refractive error may warrant lifting the flap and photoablating the posterior surface of the flap. Patients with persistent RG and no residual refractive error should be considered candidates for phototherapeutic keratectomy on the posterior flap surface. Keywords: rainbow glare, femtosecond, LASIK, keratomileusis, phototherapeutic keratectomy

  9. Variation of contrast sensitivity after femtosecond laser in situ keratomileusis in changes environments

    Directory of Open Access Journals (Sweden)

    Jing Zhou

    2015-01-01

    Full Text Available AIM: To evaluate the difference of contrast sensitivity(CSin photopic and scotopic environments in eyes with myopia and myopic astigmatism operated with femtosecond laser in situ keratomileusis(femto-LASIKand laser in situ keratomileusis(LASIK.METHODS: In a prospective study 160 myopia and myopic astigmatism patients' eyes were involved, which accepted femto-LASIK or LASIK in our hospital from January 2010 to February 2012. The myopia degree was -1.50~-10.00D, the astigmatism degree ≤-6.0D. Eighty eyes were treated with femto-LASIK in group A, and 80 eyes were treated with LASIK in group B, All patients in the treatment group completed the final 6mo of follow-up. The uncorrected visual acuity(UCVAand the best spectacle-corrected visual acuity(BSCVA, objective and manifest refractions, results of slit-lamp examination, the side effects, intraocular pressure, corneal topography, CS in photopic and scotopic environments were noted.RESULTS: All of operations on 160 cases were successful without severe complication after 6 mo follow-up. CS of femto-LASIK group(group Aat each spatial frequency environment were higher than that of LASIK group(group B. In group A, after 1mo the photopic CS, after 3mo of scotopic CS recovered to the preoperative level, 6mo after surgery improved than before the operation. In group B, after 3mo photopic CS to the preoperative level, scotopic CS at 6mo after operation was still not recovered to the preoperative level.CONCLUSION:Femto-LASIK for correction of myopia and myopic astigmatism, in improving the postoperative contrast sensitivity under shade environment has more advantages than LASIK.

  10. LASIK ablation centration: an objective digitized assessment and comparison between two generations of an excimer laser.

    Science.gov (United States)

    Kanellopoulos, Anastasios John; Asimellis, George

    2015-03-01

    To objectively define the effective centration of myopic femtosecond laser-assisted LASIK ablation pattern, evaluate the difference between achieved versus planned excimer laser ablation centration, and compare these results from two different generations of an excimer laser system. The study retrospectively evaluated 280 eyes subjected to myopic LASIK. Digital image analysis was performed on Scheimpflug sagittal curvature maps (difference of preoperative to postoperative). Centration was assessed via proprietary software digital analysis of the coordinate displacement between the achieved ablation geometric center and the planned ablation center, which was the corneal vertex. Results from two different excimer laser generations (Eye-Q 400 [140 eyes] and EX500 [140 eyes]; Alcon/WaveLight, Fort Worth, TX) were compared. Radial displacement was on average 360 ± 220 µm (range: 0 to 1,030 µm) in the Eye-Q 400 laser group and 120 ± 110 µm (range: 0 to 580 µm) in the EX500 laser group (P laser group and 4% in the EX500 laser group. Displacement of ablation pattern may depend on the laser platform used. The improvement in the efficiency of centration indicates that newer generation excimer lasers with faster eye tracking and active centration control appear to achieve a significantly more accurate centration of myopic ablation patterns. The authors propose this novel, objective technique for laser refractive surgeon evaluation may point out significant outcome measures not currently used in standard metrics of refractive laser efficiency. Copyright 2015, SLACK Incorporated.

  11. Average power scaling of UV excimer lasers drives flat panel display and lidar applications

    Science.gov (United States)

    Herbst, Ludolf; Delmdahl, Ralph F.; Paetzel, Rainer

    2012-03-01

    Average power scaling of 308nm excimer lasers has followed an evolutionary path over the last two decades driven by diverse industrial UV laser microprocessing markets. Recently, a new dual-oscillator and beam management concept for high-average power upscaling of excimer lasers has been realized, for the first time enabling as much as 1.2kW of stabilized UV-laser average output power at a UV wavelength of 308nm. The new dual-oscillator concept enables low temperature polysilicon (LTPS) fabrication to be extended to generation six glass substrates. This is essential in terms of a more economic high-volume manufacturing of flat panel displays for the soaring smartphone and tablet PC markets. Similarly, the cost-effective production of flexible displays is driven by 308nm excimer laser power scaling. Flexible displays have enormous commercial potential and can largely use the same production equipment as is used for rigid display manufacturing. Moreover, higher average output power of 308nm excimer lasers aids reducing measurement time and improving the signal-to-noise ratio in the worldwide network of high altitude Raman lidar stations. The availability of kW-class 308nm excimer lasers has the potential to take LIDAR backscattering signal strength and achievable altitude to new levels.

  12. Time Evolution of the Excimer State of a Conjugated Polymer Laser

    Directory of Open Access Journals (Sweden)

    Wafa Musa Mujamammi

    2017-11-01

    Full Text Available An excited dimer is an important complex formed in nano- or pico-second time scales in many photophysics and photochemistry applications. The spectral and temporal profile of the excimer state of a laser from a new conjugated polymer, namely, poly (9,9-dioctylfluorenyl-2,7-diyl (PFO, under several concentrations in benzene were investigated. These solutions were optically pumped by intense pulsed third-harmonic Nd:YAG laser (355-nm to obtain the amplified spontaneous emission (ASE spectra of a monomer and an excimer with bandwidths of 6 and 7 nm, respectively. The monomer and excimer ASEs were dependent on the PFO concentration, pump power, and temperature. Employing a sophisticated picosecond spectrometer, the time evolution of the excimer state of this polymer, which is over 400 ps, can be monitored.

  13. Combined intrastromal astigmatic keratotomy and laser in situ keratomileusis flap followed by photoablation to correct post-penetrating keratoplasty ametropia and high astigmatism: One-year follow-up.

    Science.gov (United States)

    Shalash, Riad B; Elshazly, Malak I; Salama, Marwa M

    2015-10-01

    To evaluate a new technique combining intrastromal astigmatic keratotomy (AK) with a laser in situ keratomileusis (LASIK) flap followed by excimer laser photoablation to correct post-penetrating keratoplasty (PKP) high astigmatism and ametropia. Kasr El Aini Hospital, Cairo University, Cairo, Egypt. Prospective interventional uncontrolled case series. Patients with post-PKP high astigmatism and ametropia had paired intrastromal AK with LASIK flap using the M2 microkeratome followed 2 to 3 months later by excimer laser photoablation. The main outcome measures were uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), mean refractive spherical equivalent (SE), and mean cylinder after each step and at the 1-year follow-up. The study comprised 20 eyes (20 patients). All parameters were significantly improved in all patients by the last follow-up visit. The mean UDVA improved from 1.07 logMAR ± 0.2 (SD) preoperatively to 0.23 ± 0.18 logMAR (P astigmatism and ametropia following PKP; however, epithelial ingrowth requiring intervention is a complication to be considered. No author has a financial or proprietary interest in any material or method mentioned. Copyright © 2015 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  14. All-Solid-State Drivers for High Power Excimer Lasers Used in Projection Gas Immersion Laser Doping

    National Research Council Canada - National Science Library

    Jacob, Jonah

    2001-01-01

    .... P-GILD uses a pulsed, 200-watt-class excimer laser as an illumination source to produce ultra-shallow, low-sheet resistance, box-like and retrograde impurity profiles in silicon without the use...

  15. A comparison of the characteristics of excimer and femtosecond laser ablation of acrylonitrile butadiene styrene (ABS)

    Energy Technology Data Exchange (ETDEWEB)

    See, Tian Long, E-mail: tianlong.see@postgrad.manchester.ac.uk [Corrosion and Protection Centre, School of Materials, The Mill, The University of Manchester, M13 9PL Manchester (United Kingdom); Laser Processing Research Centre, School of Mechanical, Aerospace and Civil Engineering, The University of Manchester, M13 9PL Manchester (United Kingdom); Liu, Zhu [Corrosion and Protection Centre, School of Materials, The Mill, The University of Manchester, M13 9PL Manchester (United Kingdom); Li, Lin [Laser Processing Research Centre, School of Mechanical, Aerospace and Civil Engineering, The University of Manchester, M13 9PL Manchester (United Kingdom); Zhong, Xiang Li [Corrosion and Protection Centre, School of Materials, The Mill, The University of Manchester, M13 9PL Manchester (United Kingdom)

    2016-02-28

    Highlights: • Ablation threshold for excimer laser is lower compared to femtosecond laser. • Effective optical penetration depth for excimer laser is lower compared to femtosecond laser. • Two ablation characteristic regimes are observed for femtosecond laser ablation. • Reduction of C=C bond following excimer or fs laser ablation is observed. • Addition of oxygen- and nitrogen-rich functional groups is observed. - Abstract: This paper presents an investigation on the ablation characteristics of excimer laser (λ = 248 nm, τ = 15 ns) and femtosecond laser (λ = 800 nm, τ = 100 fs) on ABS polymer sheets. The laser–material interaction parameters (ablation threshold, optical penetration depth and incubation factor) and the changes in material chemical properties were evaluated and compared between the two lasers. The work shows that the ablation threshold and effective optical penetration depth values are dependent on the wavelength of laser beam (photon energy) and the pulse width. The ablation threshold value is lower for the excimer laser ablation of ABS (F{sub th} = 0.087 J/cm{sup 2}) than that for the femtosecond laser ablation of ABS (F{sub th} = 1.576 J/cm{sup 2}), demonstrating a more dominating role of laser wavelength than the pulse width in influencing the ablation threshold. The ablation depth versus the logarithmic scale of laser fluence shows two linear regions for the fs laser ablation, not previously known for polymers. The effective optical penetration depth value is lower for excimer laser ablation (α{sup −1} = 223 nm) than that for femtosecond laser ablation (α{sup −1} = 2917 nm). The ablation threshold decreases with increasing number of pulses (NOP) due to the chain scission process that shortens the polymeric chains, resulting in a weaker polymeric configuration and the dependency is governed by the incubation factor. Excimer laser treatment of ABS eliminates the C=C bond completely through the chain scission process whereas

  16. KrF excimer laser precision machining of hard and brittle ceramic biomaterials.

    Science.gov (United States)

    Huang, Yao-Xiong; Lu, Jian-Yi; Huang, Jin-Xia

    2014-06-01

    KrF excimer laser precision machining of porous hard-brittle ceramic biomaterials was studied to find a suitable way of machining the materials into various desired shapes and sizes without distorting their intrinsic structure and porosity. Calcium phosphate glass ceramics (CPGs) and hydroxyapatite (HA) were chosen for the study. It was found that KrF excimer laser can cut both CPGs and HA with high efficiency and precision. The ablation rates of CPGs and HA are respectively 0.081 µm/(pulse J cm(-2)) and 0.048 µm/(pulse  J cm(-2)), while their threshold fluences are individually 0.72 and 1.5 J cm(-2). The cutting quality (smoothness of the cut surface) is a function of laser repetition rate and cutting speed. The higher the repetition rate and lower the cutting speed, the better the cutting quality. A comparison between the cross sections of CPGs and HA cut using the excimer laser and using a conventional diamond cutting blade indicates that those cut by the excimer laser could retain their intrinsic porosity and geometry without distortion. In contrast, those cut by conventional machining had distorted geometry and most of their surface porosities were lost. Therefore, when cutting hard-brittle ceramic biomaterials to prepare scaffold and implant or when sectioning them for porosity evaluation, it is better to choose KrF excimer laser machining.

  17. High efficiency metal marking with CO2 laser and glass marking with excimer laser

    DEFF Research Database (Denmark)

    Bastue, Jens; Olsen, Flemmming Ove

    1997-01-01

    with a thoroughly tested ray-tracing model is presented and compared with experimental results. Special emphasis is put on two different applications namely marking in metal with TEA-CO2 laser and marking in glass with excimer laser. The results are evaluated on the basis of the achievable energy enhancement......Today, mask based laser materials processing and especially marking is widely used. However, the energy efficiency in such processes is very low [1].This paper gives a review of the results, that may be obtained using the energy enhancing technique [1]. Results of simulations performed...

  18. Laser in situ keratomileusis in patients with collagen vascular disease: a review of the literature

    Directory of Open Access Journals (Sweden)

    Simpson RG

    2012-11-01

    Full Text Available Rachel G Simpson,1 Majid Moshirfar,2 Jason N Edmonds,2 Steven M Christiansen,2 Nicholas Behunin21The University of Arizona College of Medicine, Phoenix, AZ, USA; 2John A Moran Eye Center, The University of Utah School of Medicine, Salt Lake City, UT, USAPurpose: To evaluate the current United States Food and Drug Administration (FDA recommendations regarding laser in situ keratomileusis (LASIK surgery in patients with collagen vascular diseases (CVD and assess whether these patients make appropriate candidates for laser vision correction, and offer treatment recommendations based on identified clinical data.Methods: A literature search was conducted using PubMed, Medline, and Ovid to identify all existing studies of LASIK in patients with collagen vascular diseases. The search was conducted without date limitations. Keywords used for the search included MeSH terms: laser in situ keratomileusis, LASIK, refractive surgery, ocular surgery, and cataract surgery connected by "and" with the following MeSH and natural-language terms: collagen vascular disease, rheumatic disease, systemic disease, rheumatoid arthritis, systemic lupus erythematosus, Sjögren's syndrome, seronegative spondyloarthropathy, HLA B27, ankylosing spondylitis, reactive arthritis, psoriatic arthritis. The abstracts for all studies meeting initial search criteria were reviewed; relevant studies were included. No prospective studies were found; however, four retrospective case studies were identified that examined LASIK surgery in patients with CVD. Several case reports were also identified in similar fashion.Results: The FDA considers CVD a relative contraindication to LASIK surgery, due largely to the ocular complications associated with disease in the CVD spectrum. However, recent studies of LASIK in patients with CVD indicate LASIK may be safe for patients with very well-controlled systemic disease, minimal ocular manifestations, and no clinical signs or history of dry

  19. Performance characteristics of an excimer laser (XeCl) with single ...

    Indian Academy of Sciences (India)

    Performance characteristics of an excimer laser (XeCl) with single-stage magnetic pulse compression suitable for material processing applications are presented here. The laser incorporates in-built compact gas circulation and gas cooling to ensure fresh gas mixture between the electrodes for repetitive operation.

  20. Performance characteristics of an excimer laser (XeCl) with single ...

    Indian Academy of Sciences (India)

    2017-01-10

    Jan 10, 2017 ... Abstract. Performance characteristics of an excimer laser (XeCl) with single-stage magnetic pulse compres- sion suitable for material processing applications are presented here. The laser incorporates in-built compact gas circulation and gas cooling to ensure fresh gas mixture between the electrodes for ...

  1. Mesoscale Laser Processing using Excimer and Short-Pulse Ti: Sapphire Lasers

    Energy Technology Data Exchange (ETDEWEB)

    Shirk, M D; Rubenchik, A M; Gilmer, G H; Stuart, B C; Armstrong, J P; Oberhelman, S K; Baker, S L; Nikitin, A J; Mariella, R P

    2003-07-28

    Targets to study high-energy density physics and inertial confinement fusion processes have very specific and precise tolerances that are pushing the state-of-the-art in mesoscale microsculpting technology. A significant effort is required in order to advance the capabilities to make these targets with very challenging geometries. Ultrashort pulsed (USP) Ti:Sapphire lasers and excimer lasers are proving to be very effective tools in the fabrication of the very small pieces that make up these targets. A brief description of the dimensional and structural requirements of these pieces will be presented, along with theoretical and experimental results that demonstrate to what extent these lasers are achieving the desired results, which include sub-{mu}m precision and RMS surface values well below 100 nm. This work indicates that excimer lasers are best at sculpting the polymer pieces and that the USP lasers work quite well on metal and aerogel surfaces, especially for those geometries that cannot be produced using diamond machining and where material removal amounts are too great to do with focused ion beam milling in a cost effective manner. In addition, the USP laser may be used as part of the procedure to fill target capsules with fusion fuel, a mixture of deuterium and tritium, without causing large perturbations on the surface of the target by keeping holes drilled through 125 {micro}m of beryllium below 5 {micro}m in diameter.

  2. Excimer laser-induced metallization for in situ processing on Si and GaAs

    Energy Technology Data Exchange (ETDEWEB)

    Meunier, Michel; Suys, Marc; Tabbal, Maleck; Izquierdo, Ricardo; Yelon, Arthur; Sacher, Edward (Groupe des Couches Minces and Dept. de Genie Physique, Ecole Polytechnique de Montreal, Station ' A' , Montreal, Quebec (Canada))

    1994-05-15

    We have investigated both the large area excimer laser-induced deposition of W and its silicides on GaAs to form thermally stable Schottky contacts, and the reduction of a Cu(I) compound for the deposition of Cu interconnects for Si microelectronics. Using a KrF excimer laser at 25 mJ/cm[sup 2] and a mixture of WF[sub 6], SiH[sub 4] and Ar, metallic W is deposited with an average growth rate of 1 A/pulse. For Cu deposition, the reduction by H[sub 2] of the precursor Cu(hfac)(TMVS) under a KrF excimer laser illumination of 9 mJ/cm[sup 2] gives metallic Cu with a Cu/C ratio of 4.35. For both processes, possible deposition mechanisms are discussed in terms of gas phase and surface reactions

  3. Effects of laser in situ keratomileusis on mental health-related quality of life

    Directory of Open Access Journals (Sweden)

    Tounaka-Fujii K

    2016-09-01

    Full Text Available Kaoru Tounaka-Fujii,1 Kenya Yuki,2 Kazuno Negishi,2 Ikuko Toda,3 Takayuki Abe,4 Keisuke Kouyama,4 Kazuo Tsubota2 1Health Center, Keio University, 2Department of Ophthalmology, Keio University School of Medicine, 3Minamiaoyama Eye Clinic, 4Center for Clinical Research, Keio University School of Medicine, Tokyo, Japan Purpose: The aims of our study were to investigate whether laser in situ keratomileusis (LASIK improves health-related quality of life (HRQoL and to identify factors that affect postoperative HRQoL. Materials and methods: A total of 213 Japanese patients who underwent primary LASIK were analyzed in this study. The average age of patients was 35.0±9.4 years. The subjects were asked to answer questions regarding subjective quality of vision, satisfaction, and quality of life (using the Japanese version of 36-Item Short Form Health Survey Version 2 at three time points: before LASIK, 1 month after LASIK, and 6 months after LASIK. Longitudinal changes over 6 months in the outputs of mental component summary (MCS score and the physical component summary (PCS score from the 36-Item Short Form Health Survey Version 2 questionnaire were compared between time points using a linear mixed-effects model. Delta MCS and PCS were calculated by subtracting the postoperative score (1 month after LASIK from the preoperative score. Preoperative and postoperative factors associated with a change in the MCS score or PCS score were evaluated via a linear regression model. Results: The preoperative MCS score was 51.0±9.4 and increased to 52.0±9.8 and 51.5±9.6 at 1 month and 6 months after LASIK, respectively, and the trend for the change from baseline in MCS through 6 months was significant (P=0.03. PCS score did not change following LASIK. Delta MCS was significantly negatively associated with preoperative spherical equivalent, axial length, and postoperative quality of vision, after adjusting for potential confounding factors. Conclusion

  4. Ablação corneana baseada em topografia para correção das descentralizações pós-laser in situ keratomileusis: relato de três casos Topographically supported customized ablation for the treatment of decentered laser in situ keratomileusis: report of three cases

    Directory of Open Access Journals (Sweden)

    Vinícius Coral Ghanem

    2007-02-01

    Full Text Available Foram descritos três casos de pacientes submetidos à ablação corneana baseada em topografia para a correção das descentralizações pós-laser in situ keratomileusis, com sucesso pós-operatório.Three cases of decentered laser in situ keratomileusis were succefully treated with the topographically supported customized ablation.

  5. A comparison of the characteristics of excimer and femtosecond laser ablation of acrylonitrile butadiene styrene (ABS)

    Science.gov (United States)

    See, Tian Long; Liu, Zhu; Li, Lin; Zhong, Xiang Li

    2016-02-01

    This paper presents an investigation on the ablation characteristics of excimer laser (λ = 248 nm, τ = 15 ns) and femtosecond laser (λ = 800 nm, τ = 100 fs) on ABS polymer sheets. The laser-material interaction parameters (ablation threshold, optical penetration depth and incubation factor) and the changes in material chemical properties were evaluated and compared between the two lasers. The work shows that the ablation threshold and effective optical penetration depth values are dependent on the wavelength of laser beam (photon energy) and the pulse width. The ablation threshold value is lower for the excimer laser ablation of ABS (Fth = 0.087 J/cm2) than that for the femtosecond laser ablation of ABS (Fth = 1.576 J/cm2), demonstrating a more dominating role of laser wavelength than the pulse width in influencing the ablation threshold. The ablation depth versus the logarithmic scale of laser fluence shows two linear regions for the fs laser ablation, not previously known for polymers. The effective optical penetration depth value is lower for excimer laser ablation (α-1 = 223 nm) than that for femtosecond laser ablation (α-1 = 2917 nm). The ablation threshold decreases with increasing number of pulses (NOP) due to the chain scission process that shortens the polymeric chains, resulting in a weaker polymeric configuration and the dependency is governed by the incubation factor. Excimer laser treatment of ABS eliminates the Cdbnd C bond completely through the chain scission process whereas Cdbnd C bond is partially eliminated through the femtosecond laser treatment due to the difference in photon energy of the two laser beams. A reduction in the Cdbnd C bond through the chain scission process creates free radical carbons which then form crosslinks with each other or react with oxygen, nitrogen and water in air producing oxygen-rich (Csbnd O and Cdbnd O bond) and nitrogen-rich (Csbnd N) functional groups.

  6. Femtosecond laser versus mechanical keratome flaps in wavefront-guided laser in situ keratomileusis: prospective contralateral eye study.

    Science.gov (United States)

    Durrie, Daniel S; Kezirian, Guy M

    2005-01-01

    To compare the outcomes of wavefront-guided laser in situ keratomileusis (LASIK) performed using the IntraLase femtosecond laser with the outcomes using the Hansatome mechanical microkeratome. Private clinic, Overland Park, Kansas, USA. In a prospective contralateral-eye study performed under institutional review board supervision, 51 consecutive patients (102 eyes) had bilateral wavefront-guided LASIK for myopia using the Alcon LADARVision laser. One eye of each patient was randomized to have the flap created with the IntraLase femtosecond laser and the other flap using a standard compression head Hansatome microkeratome. All other treatment parameters were the same. The IntraLase group had significantly better mean uncorrected visual acuity (UCVA) at all intervals from 1 day to 3 months postoperatively. The mean spheroequivalent at 3 months was more myopic with the Hansatome (-0.34 diopter [D] +/- 0.28 [SD]) than with the IntraLase (-0.19 +/- 0.24 D) (Prefractive outcomes after LASIK with the IntraLase femtosecond laser may be the result of differences in postoperative astigmatism and trefoil. These findings are consistent with previous findings of better astigmatic outcomes with the IntraLase laser and may have clinical significance for wavefront-guided treatments.

  7. Recovery of corneal sensitivity to mechanical and chemical stimulation after laser in situ keratomileusis.

    Science.gov (United States)

    Gallar, Juana; Acosta, M Carmen; Moilanen, Jukka A O; Holopainen, Juha M; Belmonte, Carlos; Tervo, Timo M T

    2004-01-01

    To evaluate the time course of changes in corneal sensitivity to mechanical and chemical stimuli produced by laser in situ keratomileusis (LASIK) in humans. We performed a cross-sectional study of 17 LASIK-operated eyes (VisX S2, equipped with version 2.50-3.10 software) and 15 control eyes of 17 individuals to evaluate regeneration of corneal sensitivity after LASIK. Gas pulses of variable flow and compositions were applied to the cornea by a non-contact gas esthesiometer. Mechanical stimuli consisted of air puffs at flows from 0 to 200 ml/min. Chemical stimulation was made with gas pulses containing 0% to 80% CO2 in air at subthreshold flow. Mechanical and chemical thresholds and intensity-response curves for the evoked sensations were determined prior to surgery, and 7 to 9 days, 3 to 5 months, and 1.5 to 2.5 years after surgery. Corneal sensitivity to mechanical stimulation was enhanced 7 to 9 days after surgery but subsequently dropped markedly and remained significantly below control levels 3 to 5 months after LASIK. Sensitivity to both mechanical and chemical types of stimuli was close to normal 2 years postoperatively. Corneal sensitivity decreased immediately after LASIK but mechanical sensitivity showed a transient hyperesthesia 7 to 9 days afterward. Subsequently, a long-lasting and deep hypoesthesia to mechanical and chemical stimuli was observed. Gas esthesiometry revealed that disturbances of corneal sensation still exist at times when coarse mechanical sensitivity appeared to be normal.

  8. Laser in situ keratomileusis surgery is not safe for military personnel.

    Science.gov (United States)

    Xiao, Jian-He; Zhang, Mao-Nian; Jiang, Cai-Hui; Zhang, Ying; Qiu, Huai-Yu

    2012-01-01

    To investigate the relationship between eye injury and laser in-situ keratomileusis (LASIK) surgery in military personnel. This retrospective study collected the data from 27 evacuation hospitals of Chinese army. All medical records of eye injuries in military personnel admitted to the 27 hospitals between January 2006 and December 2010 were reviewed. Patients'detailed information was analyzed, including the injury time, place, type, cause, as well as examination, treatment and outcome. There were 72 eye-injured patients who had been treated by LASIK before. The incidence was rising year by year. Among them, 69 patients were diagnosed with mechanical ocular injury and 3 with non-mechanical ocular injury; 29 patients had traumatic flap-related complications and 21 patients need surgery. There was statistical difference when compared with those having no refractive surgery history. Visual acuity recovered well at discharge. There is a high risk of potential traumatic flap problems after LASIK and it is not recommended in army service.

  9. Intracorneal rings to correct corneal ectasia after laser in situ keratomileusis.

    Science.gov (United States)

    Alió, Jorge; Salem, Tamer; Artola, Alberto; Osman, Amr

    2002-09-01

    To evaluate the potential of using intrastromal corneal ring technology (Intacs, KeraVision) to correct posterior ectasia after laser in situ keratomileusis (LASIK) for myopia. Department of Cornea and Refractive Surgery, Instituto Oftalmológico de Alicante, and Miguel Hernández University School of Medicine, Alicante, Spain. In this prospective noncomparative intervention case series, Intacs segments were implanted in 3 eyes that developed posterior ectasia after myopic LASIK with clear central corneas. Posterior ectasia and corneal thickness were tested using the Orbscan II Slit Scanning Corneal Topography/Pachymetry System (Orbtek Inc.). Segment thickness varied based on corneal topography analysis and refraction. The mean follow-up was 8.3 months (range 7 to 11 months). The cases showed marked improvement after Intacs segment implantation. Postoperatively, there was a reduction in the magnitude of the posterior and anterior corneal surface steepening or ectasia and an increase in the topographical regularity index. In addition, the significantly enlarged optical zones resulted in a favorable visual outcome. In 2 eyes, the uncorrected visual acuity (UCVA) was 20/40 postoperatively. In the third eye, there was a residual refractive error; the UCVA was 20/50 and the best spectacle-corrected visual acuity, 20/40. Intacs intrastromal corneal rings used as a mechanical device may alter the biomechanical properties of the cornea for the correction of iatrogenic keratectasia and the associated residual myopia.

  10. Role of the bandage soft contact lens in the postoperative laser in situ keratomileusis patient.

    Science.gov (United States)

    Ahmed, I I; Breslin, C W

    2001-12-01

    To determine whether a bandage soft contact lens (BSCL) is routinely needed in the postoperative laser in situ keratomileusis (LASIK) patient and whether topical tetracaine 0.5% or diclofenac sodium 0.1% (Voltaren) is more effective in relieving patient discomfort than a BSCL. LCA-Vision Center, Toronto, Ontario, Canada. In this prospective randomized comparative study, all patients had bilateral simultaneous LASIK procedures. Post-LASIK patient comfort was evaluated through 3 arms of the study: BSCL versus no BSCL, 40 consecutive patients with 1 eye randomized to receive a BSCL and no BSCL in the fellow eye; BSCL versus tetracaine 0.5%, 26 consecutive patients with 1 eye randomized to receive a BSCL and tetracaine 0.5% in the fellow eye; tetracaine 0.5% versus Voltaren, 54 consecutive patients with 1 eye randomized to receive tetracaine 0.5% and Voltaren in the fellow eye. The patient preferences after LASIK were as follows: BSCL versus no BSCL-12 (30%) versus 23 (58%) (P =.062); BSCL versus tetracaine 0.5%-4 (15%) versus 22 (85%) (P <.001). On average, the eyes with no BSCL had a 2-line improvement in uncorrected visual acuity over the BSCL eyes. Tetracaine 0.5% versus Voltaren-13 (24%) versus 21 (39%) (P =.170). The routine use of a BSCL in the postoperative LASIK patient is not necessary. Voltaren and tetracaine 0.5% were safe and more effective in relieving postoperative patient discomfort and resulted in improved visual acuity immediately postoperatively.

  11. Partial flap during laser In-situ Keratomileusis: Pathogenesis and timing of retreatment

    Directory of Open Access Journals (Sweden)

    Rao Srinivas

    2000-01-01

    Full Text Available Purpose: To report the timing of retreatment and clinical outcomes in patients with a partial corneal flap during laser in-situ keratomileusis (LASIK, and to describe the causes of this complication. Methods: Retrospective review of case records of four patients (4 eyes who had a partial corneal flap during LASIK. Results: The mean age of the four patients was 23 ± 4.7 years, and mean preoperative spherical equivalent (SE refraction was -9.1 ± 3.1D (range, -5.5 to -13D. A 160 μm corneal flap was attempted during the initial treatment. Retreatment with a 180 μm corneal flap was performed at a mean of 5.1 ± 1.6 weeks (range, 4 to 7.5 weeks after the initial procedure. There were no intraoperative complications during retreatment. Post-LASIK mean SE refraction was -1.0 ± 1.1D (range, +0.38 to -2.0D, after a mean follow up of 19 ± 15.7 weeks (range, 7 to 42 weeks. Best spectacle-corrected visual acuity decreased in one eye from 6/5 to 6/6 and was maintained in the others. Conclusion: LASIK retreatment can be performed as early as one month after a partial flap, if the refraction is stable and a thicker corneal flap is created.

  12. A case of intractable infectious keratitis and subsequent flap necrosis after laser in situ keratomileusis

    Directory of Open Access Journals (Sweden)

    Kazutaka Kamiya

    2009-09-01

    Full Text Available Kazutaka Kamiya, Masayuki Kasahara, Kimiya ShimizuDepartment of Ophthalmology, University of Kitasato School of Medicine, JapanAbstract: We report on a patient in whom intractable infectious keratitis and subsequent lamellar flap necrosis necessitating flap amputation after laser in situ keratomileusis (LASIK. A 34-year-old woman undergoing LASIK complained of blurred vision and pain in the left eye. The best spectacle-corrected visual acuity was 0.01, and slit-lamp examination showed a marked presence of stromal infiltrates involving the flap and the underlying stroma in that eye. The patient was treated topically with hourly instillation of micronomicin, levofloxacin, and cefmenoxime, together with systemic administration of imipenem, but the left eye developed corneal flap necrosis. We performed surgical debridement of the diseased stroma and excised the lamellar flap. Since nontuberculous mycobacterium was detected on the surgical instruments, we then added oral clarithromycin, and substituted systemic administration of amikacin with that of imipenem. At one month after the flap removal, the visual acuity gradually improved to 0.7, but the stromal opacity of the central cornea and hyperopic shift of +3.0 diopters remained. LASIK can cause intractable keratitis, resulting in significant visual disturbance that presumably results from insufficient antisepsis of the medical instruments used for this surgery, supporting the importance of strict sterilization of these instruments.Keywords: infectious keratitis, flap necrosis, nontuberculous mycobacterium, sterilization, LASIK

  13. Comparison of the changes in corneal biomechanical properties after photorefractive keratectomy and laser in situ keratomileusis.

    Science.gov (United States)

    Kamiya, Kazutaka; Shimizu, Kimiya; Ohmoto, Fumiko

    2009-08-01

    To compare the postoperative biomechanical properties of the cornea after photorefractive keratectomy (PRK) and after laser in situ keratomileusis (LASIK) in eyes with myopia. We retrospectively examined 27 eyes of 16 patients undergoing PRK and 31 eyes of 16 patients undergoing LASIK for the correction of myopia. Corneal hysteresis (CH) and corneal resistance factor (CRF) were measured with Ocular Response Analyzer before and 3 months after surgery. We also investigated the relationship between these biomechanical changes and the amount of myopic correction. The CH was decreased significantly from 10.8 +/- 1.3 (mean +/- SD) mmHg to 9.2 +/- 1.6 mmHg after PRK (P biomechanical properties after PRK (r = -0.61, P biomechanical strength of the cornea depending on the amount of myopic correction. The amount of biomechanical changes is larger after LASIK than after PRK. From a biomechanical viewpoint, PRK may be a less invasive surgical approach for the correction of myopia than LASIK.

  14. Apparent progression of presbyopia after laser in situ keratomileusis in patients with early presbyopia.

    Science.gov (United States)

    Tsuneyoshi, Yukari; Negishi, Kazuno; Saiki, Megumi; Toda, Ikuko; Tsubota, Kazuo

    2014-08-01

    To assess the effect of laser in situ keratomileusis (LASIK) on near visual function in presbyopic patients. Retrospective cohort study. Fifty-three eyes of 40 patients 45 years of age and older who had undergone LASIK for high myopia (-6 diopters [D] and over) were included. The minimal add powers for obtaining the best-corrected near visual acuity (add powers) were measured preoperatively and 3 months postoperatively, and the correlations with the powers corrected by LASIK, corneal higher-order aberrations (HOAs), ocular HOAs, and patient ages were evaluated using univariate analysis. Factors correlated with the changes in add powers were evaluated further by multivariate analysis. The mean ± standard deviation patient age was 50.0 ± 4.1 years; the power corrected by LASIK was -7.56 ± 1.06 D. The mean add power was 1.80 ± 0.60 D preoperatively, which increased significantly (P  .05). Multivariate analysis showed that only age was correlated significantly (P = .01). The percentage of eyes with increased add powers of 0.5 D or more was 60.4%, which was significantly (P = .02) higher in younger patients. This study verified the apparent progression of presbyopia after LASIK and the importance of obtaining informed consent from patients, especially those with early presbyopia. Copyright © 2014 Elsevier Inc. All rights reserved.

  15. Factors Influencing Intraocular Pressure Changes after Laser In Situ Keratomileusis with Flaps Created by Femtosecond Laser or Mechanical Microkeratome.

    Directory of Open Access Journals (Sweden)

    Meng-Yin Lin

    Full Text Available The aim of this study is to describe factors that influence the measured intraocular pressure (IOP change and to develop a predictive model after myopic laser in situ keratomileusis (LASIK with a femtosecond (FS laser or a microkeratome (MK. We retrospectively reviewed preoperative, intraoperative, and 12-month postoperative medical records in 2485 eyes of 1309 patients who underwent LASIK with an FS laser or an MK for myopia and myopic astigmatism. Data were extracted, such as preoperative age, sex, IOP, manifest spherical equivalent (MSE, central corneal keratometry (CCK, central corneal thickness (CCT, and intended flap thickness and postoperative IOP (postIOP at 1, 6 and 12 months. Linear mixed model (LMM and multivariate linear regression (MLR method were used for data analysis. In both models, the preoperative CCT and ablation depth had significant effects on predicting IOP changes in the FS and MK groups. The intended flap thickness was a significant predictor only in the FS laser group (P < .0001 in both models. In the FS group, LMM and MLR could respectively explain 47.00% and 18.91% of the variation of postoperative IOP underestimation (R2 = 0.47 and R(2 = 0.1891. In the MK group, LMM and MLR could explain 37.79% and 19.13% of the variation of IOP underestimation (R(2 = 0.3779 and 0.1913 respectively. The best-fit model for prediction of IOP changes was the LMM in LASIK with an FS laser.

  16. Wound healing in rabbit corneas after photorefractive keratectomy and laser in situ keratomileusis.

    Science.gov (United States)

    Miyamoto, Takeshi; Saika, Shizuya; Yamanaka, Akio; Kawashima, Yoshiji; Suzuki, Yoshitaka; Ohnishi, Yoshitaka

    2003-01-01

    To compare the wound-healing process in the rabbit cornea after photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) with the same refractive correction. Department of Ophthalmology, Wakayama Medical University, Wakayama, Japan. Adult albino rabbits (N = 24) were used. One eye of each animal had PRK or LASIK with the same refractive correction. Each animal was killed after an interval of up to 6 months. The expression pattern of corneal stromal injury-related molecules with the 2 treatments were compared. Paraffin sections of the cornea were processed immunohistochemically for alpha-smooth muscle actin (alpha-SMA), collagen type IV [alpha1(IV)](2),alpha2(IV), and heat shock protein (HSP) 47 as well as other HSPs. Sections were also examined after hematoxylin and eosin or periodic acid-Schiff staining. Hematoxylin and eosin staining showed the central epithelium to be thick in PRK-treated corneas. The thick epithelium was restricted to the area around the corneal flap edge adhesion in LASIK-treated corneas at 3 months. Periodic acid-Schiff staining showed an absence of or interruption in the epithelial basement membrane in PRK-treated corneas for up to 6 months. Heat shock protein 47 was detected in keratocytes on day 3 but not after that in PRK-treated corneas. There was no difference in the expression of other HSPs. Alpha-smooth muscle actin was expressed in keratocytes repopulated in the central anterior cornea of PRK-treated corneas at 28 days. Keratocytes with immunoreactivity for these 2 proteins were not seen in LASIK-treated corneas. Collagen IV [alpha1(IV)](2),alpha2(IV) was not detected in either group of corneas. The central epithelium became transiently thicker in PRK-treated corneas. Keratocyte responses to laser stromal ablation were more marked in corneas treated with PRK than in those treated with LASIK.

  17. Discharge instabilities in high-pressure fluorine based excimer laser gas mixtures

    NARCIS (Netherlands)

    Mathew, D.

    2007-01-01

    Fluorine based excimer lasers such as KrF, ArF and F2 are currently the most powerful sources available in the ultraviolet wavelength range, operating at 248 nm, at 193 nm and at 157 nm, respectively. They are thus of central importance for numerous applications in this range. At these short

  18. A new method for three dimensional excimer laser micromachining, Hole Area Modulation (HAM)

    NARCIS (Netherlands)

    Masuzawa, T.; Olde Benneker, Jeroen; Eindhoven, J.J.C.

    2000-01-01

    A new excimer laser system configuration for three dimensional (3D) micromachining, called Hole Area Modulation (HAM) method, is proposed and the feasibility of the system is experimentally confirmed. In this method, information on the depth of machining is converted to the sizes of small holes in

  19. Saline flush during excimer laser angioplasty: short and long term effects in the rabbit femoral artery

    NARCIS (Netherlands)

    van Leeuwen, T. G.; Velema, E.; Pasterkamp, G.; Post, M. J.; Borst, C.

    1998-01-01

    BACKGROUND AND OBJECTIVE: In this study, the effect of flushing saline on arterial wall damage (medial ruptures and necrosis), intimal hyperplasia, and arterial remodeling was determined. During excimer laser coronary angioplasty saline is flushed to reduce the size of explosive water vapor bubbles

  20. Preionization and gain studies in fluorine based excimer laser gas discharges

    NARCIS (Netherlands)

    Azarov, A.V.

    2008-01-01

    Fluorine-based excimer gas lasers are powerful sources of coherent radiation in the UV and VUV part of the electro-magnetic spectrum. Due to their short wavelengths and high output power they are widely employed in high resolution material processing like micromachining and in lithography. In this

  1. Refractive microlenses produced by excimer laser machining of poly(methyl methacrylate)

    DEFF Research Database (Denmark)

    Jensen, Martin Frøhling; Krühne, Ulrich; H., L.

    2005-01-01

    A method has been developed whereby refractive microlenses can be produced in poly (methyl methacrylate) by excimer laser irradiation at λ = 248 nm. The lenses are formed by a combined photochemical and thermal process. The lenses are formed as depressions in the substrate material (negative foca...

  2. Mechanism of injurious effect of excimer (308 nm) laser on the cell

    Science.gov (United States)

    Nevorotin, Alexey J.; Kallikorm, A. P.; Zeltzer, Gregory L.; Kull, Mart M.; Mihkelsoo, Virgo T.

    1991-06-01

    A Lameta 22710 excimer laser operating at 70 mJ/mm2 per pulse, with pulse duration of 70 nsec, and pulse repetition rate of 10 Hz, equipped with a quartz filament as energy conductor was used to make incisions on rat liver. 2 to 5 sec after irradiation the specimens were fixed and further processed for electron microscopy and histochemical visualization of the endoplasmic reticulum (ER) marker enzyme glucose-6- phosphatase at the ultrastructural level. The additional series were: fixation before irradiation-(A); lasing with Nd:YAG laser (1064 nm, continuous wave mode, 40 J/mm2)-(B); incision with a white-hot steel needle-(C); and incision with an Esto-Rex ultrasound scalpel (66 kHz, 6 Wt, vibration amplitude of 15 micrometers )-(D). The results showed that unlike Series C and B, in which high temperature caused severe damage to all cellular organellae, the excimer action was much more specific. It caused vesiculation of ER without significant injuries to other cellular structures. The analogous effect was noted after US scalpel cutting, thereby allowing a conclusion that a kind of dynamic rather than thermal factor is responsible for the observed phenomenon of vesiculation. The time schedule of vesicle formation and molecular background of membrane transformation is considered in the light of the data of Series A and D, and also on the basis of available information of membrane behavior. Photoablative effect of pulsed excimer laser is thought to be based on chemical decomposition of organic molecules and their ejection from the tissue to the action of high energy photons. Pressure waves (either acoustic or shock) are presumably generated powerful enough to cause tissue and cell damage beyond the site of ablation. Some thermal and fluorescence events are also implicative in biological targets irradiated with excimer lasers. In our previous studies electron histochemistry was employed for the analysis of cellular alterations caused with a continuous wave mode

  3. Review of current indications for combined very high fluence collagen cross-linking and laser in situ keratomileusis surgery

    Directory of Open Access Journals (Sweden)

    Anastasios John Kanellopoulos

    2013-01-01

    Full Text Available In this brief review we will discuss the reasoning and evolution of our current use of combined very high-fluence collagen crosslinking and laser in situ keratomileusis. Several presentations and pertinent publications are reviewed, along with the key steps of the enhanced LASIK procedure. Long term outcome data support the safety and efficacy of LASIK Xtra in stabilizing myopic but also hyperopic LASIK results.In conclusion, we have compelling evidence that LASIK Xtra is a safe and effective adjunct.

  4. Comparison of corneal sensitivity, tear function and corneal staining following laser in situ keratomileusis with two femtosecond laser platforms

    Directory of Open Access Journals (Sweden)

    Petznick A

    2013-03-01

    Full Text Available Andrea Petznick,1 Annabel Chew,2 Reece C Hall,2 Cordelia ML Chan,2 Mohamad Rosman,1,2 Donald Tan,1–3 Louis Tong,1–4 Jodhbir S Mehta1–31Singapore Eye Research Institute, Singapore; 2Singapore National Eye Centre, Singapore; 3Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore; 4Duke-NUS Graduate Medical School, SingaporePurpose: To evaluate longitudinal changes in corneal sensitivity, tear function, and corneal staining in patients who underwent laser in situ keratomileusis (LASIK using two different femtosecond lasers.Methods: In a prospective, randomized clinical trial, contralateral eyes of 45 patients underwent flap creation by either VisuMax or IntraLase™ femtosecond laser. Corneal sensitivity, tear break up time (TBUT, Schirmer’s test, and corneal fluorescein staining were assessed preoperatively and at 1 week, 1 month, and 3 months postoperatively.Results: There were no statistical differences in any clinical outcome measure between the two femtosecond lasers (P > 0.05, although there was a trend towards slightly lower reductions for corneal sensitivity and TBUT in VisuMax-operated eyes. Overall, corneal sensitivity was significantly reduced at 1 week (P 0.05.Conclusion: This study showed that changes in corneal sensitivity, tear function, and corneal staining were statistically similar in LASIK using VisuMax and IntraLase femtosecond lasers for flap creation. However, the trend towards faster recovery of corneal sensitivity and TBUT observed in VisuMax-operated eyes may be attributable to improved technical specifications.Keywords: femtosecond laser, corneal sensitivity, tear film break-up time, Schirmer’s, corneal staining

  5. Patient age, refractive index of the corneal stroma, and outcomes of uneventful laser in situ keratomileusis.

    Science.gov (United States)

    Patel, Sudi; Alió, Jorge L; Walewska, Anna; Amparo, Francisco; Artola, Alberto

    2013-03-01

    To determine the influence of age and the corneal stromal refractive index on the difference between the predicted and actual postoperative refractive error after laser in situ keratomileusis (LASIK) and whether the precision of outcomes could be improved by considering age and the refractive index. Vissum Instituto Oftalmologico de Alicante, Alicante, Spain. Case series. Flaps were created using a mechanical microkeratome. The stromal refractive index was measured using a VCH-1 refractometer after flap lifting. Refractive data were obtained 1, 3, and 6 months postoperatively. Uneventful LASIK was performed in 133 eyes. The mean age, refractive index, and applied corrections were 33.4 years ± 9.49 (SD), 1.368 ± 0.006, and -2.43 ± 3.36 diopters (D), respectively. The difference between the predicted and actual postoperative refractive error = 2.315-0.021 age-1.106 refractive index (F = 3.647, r = 0.254, P=.029; n = 109) at 1 month and = 11.820-0.023 age-7.976 refractive index (F = 3.392, r = 0.261, P=.022, n = 106) at 3 months. A correlation between the actual and calculated postoperative refraction improved from r = -0.178 (P=.064; n = 75) to r = -0.418 (Prefractive index 6 months postoperatively. The predicted outcomes of LASIK can be improved by inputting the refractive index of the individual corneal stroma. Unexpected outcomes (>0.50 D) of LASIK could be avoided by considering patient age and the refractive index and by adjusting the applied correction accordingly. Copyright © 2012 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  6. Facilitation of amblyopia management by laser in situ keratomileusis in children with myopic anisometropia.

    Science.gov (United States)

    Ghanem, Assad A; Nematallah, Ehab H; El-Adawy, Ibrahim T; Anwar, Ghada M

    2010-04-01

    To evaluate the effects of Laser in situ keratomileusis (LASIK) in decreasing myopic anisometropia in children with spectacles or contact lens intolerance and its validity in facilitating treatment of resultant myopic anisometropic amblyopia. LASIK was performed for 18 eyes of 18 children having myopic anisometropic amblyopia not successfully treated with the standard amblyopia treatment for 6 months. Children were followed up at 1 week, 1, 2, 6, 12, 18, and 24 months. Postoperative amblyopia therapy was continued with occlusion of the dominant eye for 6 hr daily for the first 3 months and then for 4 hr per day as long as possible. The mean spherical equivalent refraction in the operated eye had reduced significantly from -9.25 +/- 3.43D preoperatively to -1.5 +/- 1.23D at 2 years postoperatively. The mean spherical equivalent in the non operated fellow eye was -1.0 +/- 1.18D preoperatively and -2.25 +/- 1.05D at 2 years. The mean spherical equivalent myopic anisometropia was -7.75 +/- 2.34D preoperatively and -0.5 +/- 0.31D at 2 years, representing a 93.5% reduction in myopic anisometropia. At 6 months, 14 eyes (77.8%) were within +/-1D of the targeted refraction and at 2 years, 10 eyes (55.6%) were within +/-1.0D. The mean regression value was -2.25 +/- 1.7D, however, 15 eyes (83.3%) were within 3.0D of the fellow eye. The mean BCVA was significantly improved from 0.26 +/- 0.21 preoperatively to 0.82 +/- 0.17 by 2 years after LASIK with amblyopia treatment. LASIK is a safe and effective alternative method for correcting myopic anisometropia facilitating treatment of amblyopia, only considerd in children with spectacles or contact lens intolerance, with more improved visual acuity and binocular vision.

  7. Laser in situ keratomileusis to manage refractive errors after deep anterior lamellar keratoplasty.

    Science.gov (United States)

    Acar, Banu Torun; Utine, Canan A; Acar, Suphi; Ciftci, Ferda

    2012-06-01

    To analyze the visual and refractive outcomes of laser in situ keratomileusis (LASIK) after deep anterior lamellar keratoplasty (DALK) for keratoconus. Haydarpasa Numune Education and Research Hospital, Ophthalmology Clinic, Istanbul, Turkey. Cohort study. Patients with compound myopic astigmatism after DALK and a spherical equivalent (SE) between -2.50 diopters (D) and -8.00 D had LASIK as a single-step procedure, correcting the manifest refraction error. The visual and refractive results at 1 month, 3 months, and the last follow-up were compared with preoperative values. The mean follow-up was 11.17 months ± 3.61 (SD). The mean manifest refraction SE (MRSE) and autorefractometer measurements and the autokeratorefractometer and corneal topography keratometry readings decreased significantly from preoperatively to 1 month postoperatively (P.05). Preoperatively, the mean uncorrected (UDVA) and corrected (CDVA) distance visual acuities were 0.21 ± 0.08 and 0.73 ± 0.08, respectively; postoperatively, the means were 0.73 ± 0.10 and 0.98 ± 0.05, respectively. All eyes achieved a postoperative UDVA better than 0.5. No eye lost CDVA lines. The safety index was 1.34. The mean MRSE was -5.18 ± 1.74 D preoperatively and -1.05 ± 0.64 D postoperatively (P<.01). Postoperatively, 11 eyes (91.67%) were within ± 2.00 D of the SE, 8 (6.67%) were within ± 1.00 D, and 5 (41.67%) were within ± 0.50 D. No complications were encountered. Treatment of post-DALK keratoconus patients with LASIK to correct manifest refraction error seems to be a viable option. Copyright © 2012 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  8. Effects of laser in situ keratomileusis on mental health-related quality of life.

    Science.gov (United States)

    Tounaka-Fujii, Kaoru; Yuki, Kenya; Negishi, Kazuno; Toda, Ikuko; Abe, Takayuki; Kouyama, Keisuke; Tsubota, Kazuo

    2016-01-01

    The aims of our study were to investigate whether laser in situ keratomileusis (LASIK) improves health-related quality of life (HRQoL) and to identify factors that affect postoperative HRQoL. A total of 213 Japanese patients who underwent primary LASIK were analyzed in this study. The average age of patients was 35.0±9.4 years. The subjects were asked to answer questions regarding subjective quality of vision, satisfaction, and quality of life (using the Japanese version of 36-Item Short Form Health Survey Version 2) at three time points: before LASIK, 1 month after LASIK, and 6 months after LASIK. Longitudinal changes over 6 months in the outputs of mental component summary (MCS) score and the physical component summary (PCS) score from the 36-Item Short Form Health Survey Version 2 questionnaire were compared between time points using a linear mixed-effects model. Delta MCS and PCS were calculated by subtracting the postoperative score (1 month after LASIK) from the preoperative score. Preoperative and postoperative factors associated with a change in the MCS score or PCS score were evaluated via a linear regression model. The preoperative MCS score was 51.0±9.4 and increased to 52.0±9.8 and 51.5±9.6 at 1 month and 6 months after LASIK, respectively, and the trend for the change from baseline in MCS through 6 months was significant (P=0.03). PCS score did not change following LASIK. Delta MCS was significantly negatively associated with preoperative spherical equivalent, axial length, and postoperative quality of vision, after adjusting for potential confounding factors. Mental HRQoL is not lost with LASIK, and LASIK may improve mental HRQoL. Preoperative axial length may predict postoperative mental HRQoL.

  9. Ocular residual astigmatism: effects of demographic and ocular parameters in myopic laser in situ keratomileusis.

    Science.gov (United States)

    Frings, Andreas; Katz, Toam; Steinberg, Johannes; Druchkiv, Vasyl; Richard, Gisbert; Linke, Stephan J

    2014-02-01

    To analyze the influence of demographic and ocular factors on ocular residual astigmatism (ORA) in myopic laser in situ keratomileusis (LASIK). University Medical Center Hamburg-Eppendorf, Hamburg, Germany. Retrospective cross-sectional data analysis. Eyes of consecutive myopic patients scheduled for LASIK were studied to evaluate the influence on preexisting ORA of age, sex, ocular dominance, subjective cylinder and topographic astigmatism, subjective sphere, and mesopic pupil size. The ORA was determined using Alpins vector analysis. Two subgroups, defined by the ratio of ORA to preoperative refractive cylinder (R), were formed: ORA:R ≥ 1.0 and ORA:R patients). The mean ORA was 0.75 diopter (D) ± 0.39 (SD) (range 0.00 to 2.00 D); 1372 (46%) eyes had ORA of 1.00 D or more. Ordinary least square estimations and odds ratios showed that subjective sphere, male sex, and dominant eye were negative predictors of the degree of preoperative ORA, while increasing age and larger mesopic pupils did not indicate ORA orientation. With-the-rule astigmatism meridian was more likely in eyes with low ORA, while oblique and against-the-rule meridians were related to high ORA. The preoperative assessment of refractive surgery candidates should consider the interaction between topographic, refractive, and ORA because corneal refractive surgery is more successful in eyes in which the cylinder mainly originates from the anterior cornea. The current data can help identify patients at high risk for having a significant difference between subjective cylinder and topographic astigmatism. No author has a financial or proprietary interest in any material or method mentioned. Copyright © 2014 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  10. Photorefractive Keratectomy for Residual Myopia after Myopic Laser In Situ Keratomileusis

    Directory of Open Access Journals (Sweden)

    Kamal A. M. Solaiman

    2017-01-01

    Full Text Available Purpose. To evaluate the safety, efficacy, and predictability of photorefractive keratectomy (PRK on the corneal flap for correction of residual myopia following myopic laser in situ keratomileusis (LASIK. Patients and Methods. A retrospective study on eyes retreated by PRK on the corneal flap for residual myopia after LASIK. All eyes had no enough stroma after LASIK sufficient for LASIK enhancement. Data included spherical equivalent (SE, uncorrected and best corrected visual acuity (UCVA and BCVA, central pachymetry, corneal higher order aberrations (HOAs, corneal hysteresis (CH, corneal resistance factor (CRF, and corneal haze. Results. The study included 64 eyes. Before PRK, the mean central pachymetry was 400.21±7.8 μm, the mean SE was −1.74±0.51 D, and the mean UCVA and BCVA were 0.35±0.18 and 0.91±0.07, respectively. 12 months postoperatively, the mean central corneal thickness was 382.41±2.61 μm, the mean SE was −0.18±0.32 D (P0.5, respectively. The safety index was 1.01 and the efficacy index was 0.86. No significant change was observed in corneal HOAs. Conclusions. Residual myopia less than 3 D after LASIK could be safely and effectively treated by PRK and mitomycin C with a high predictability. This prevents postoperative ectasia and avoids the flap related complications but has no significant effect on HOAs.

  11. Bilateral Epithelial Defects after Laser in situ Keratomileusis. Clinical Features, Management and Outcome

    Directory of Open Access Journals (Sweden)

    Rao Srinivas

    2005-03-01

    Full Text Available PURPOSE: To describe the preoperative characteristics, intraoperative details, management, and postoperative in patients with bilateral epithelial defects after laser in situ keratomileusis (LASIK. METHODS: Retrospective non-comparative case series. RESULTS: Six patients with bilateral epithelial defects after LAISK were part of a cohort of 605 patients undergoing bilateral LASIK at our center from December 2001 to April 2003. The mean age of the patients (5M:1F was 28.5 7.9 years, and the average pretreatment myopic spherical equivalent (SE refraction was 7.3 0.7 D (-4, -12.25D. An epithelial flap was present in 6 eyes and an epithelial defect with a mean diameter of 3 mm (2mm, 6mm was seen in 6 eyes. In four patients the epithelial disturbance was bilaterally similar. All defects occurred in the inferior cornea and the epithelial flaps had the hinge positioned superiorly. None of the patients had ocular or systemic risk factors that could have resulted in this complication. A bandage contact lens was used in 6 eyes. At last follow-up of 5.5 9.5 months (0.25, 21 months, unaided visual acuity was 6/9 or better in 10 eyes. Best spectacle-corrected visual acuity (BSCVA was maintained in 8 eyes, while 4 eyes lost one line of BSCVA. Recurrent corneal erosions were not reported in the follow-up period. CONCLUSIONS: These patients represent a hitherto unrecognised group of individuals who appear to have a subclinical weakness of adhesion of the corneal epithelium to the underlying structures, which is not evident on clinical examination. This results in bilateral epithelial disturbances after LASIK. Appropriate management results in satisfactory clinical outcomes. Other options for treatment of the fellow eye of such patients include the use of a different microkeratome, release of suction during the reverse pass of the Hansatome microkeratome, and photorefractive keratectomy if the refractive error is low.

  12. Laser in situ keratomileusis flap-thickness predictability with a pendular microkeratome.

    Science.gov (United States)

    Paschalis, Eleftherios I; Labiris, Georgios; Aristeidou, Antonis P; Foudoulakis, Nikitas C; Koukoula, Stavrenia C; Kozobolis, Vassilios P

    2011-12-01

    To assess flap-thickness predictability with a pendular microkeratome (130 μm head). Eye Institute of Thrace, Democritus University of Thrace, Alexandroupolis, Greece. Clinical trials. The study comprised 263 eyes (132 patients). Laser in situ keratomileusis was performed using the 130 μm head of the Carriazo pendular microkeratome; right eyes were treated first. Ultrasound pachymetry and topography were used for central corneal thickness (CCT) and keratometry (K) measurements. Evaluation included flap thickness, flap diameter, and flap shape. The mean flap thickness was 125 μm ± 22 (SD) (range 74 to 187 μm) in right eyes and 112 ± 21 μm (range 61 to 190 μm) in left eyes. Flap thickness was significantly correlated with preoperative CCT (r = 0.271; P.15). Right eyes had thicker flaps than left eyes (P<.001); both were significantly below the 130 μm head thickness (mean flap thickness 119.2 ± 22.8 μm; P<.001). The mean achieved flap diameter was 9.2 mm using the 9.0 ring and 9.8 mm using the 10.0 mm ring. Flap-thickness stabilization and convergence between right eyes and left eyes occurred after 100 consecutive flap cuts. Flap-thickness predictability was influenced by preoperative CCT only. All cuts were significantly thinner than the head thickness regardless of the suction ring size. Second surgical eyes had thinner flaps, possibly from blade deterioration from the first cut. Approximately 100 flaps were required as a learning curve. Copyright © 2011 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  13. Preionization and gain studies in fluorine based excimer laser gas discharges

    OpenAIRE

    Azarov, A.V.

    2008-01-01

    Fluorine-based excimer gas lasers are powerful sources of coherent radiation in the UV and VUV part of the electro-magnetic spectrum. Due to their short wavelengths and high output power they are widely employed in high resolution material processing like micromachining and in lithography. In this field pattern sizes several times shorter than the used wavelength can be achieved using an immersion technique. However due to the short duration of the laser pulse (typically of few tens of ns for...

  14. Topography-guided hyperopic and hyperopic astigmatism femtosecond laser-assisted LASIK: long-term experience with the 400 Hz eye-Q excimer platform

    Directory of Open Access Journals (Sweden)

    Kanellopoulos AJ

    2012-06-01

    Full Text Available Anastasios John KanellopoulosDepartment of Ophthalmology, New York University Medical School, New York, NY, and LaserVision.gr Eye Institute, Athens, GreeceBackground: The purpose of this study was to evaluate the safety and efficacy of topography-guided ablation using the WaveLight 400 Hz excimer laser in laser-assisted in situ keratomileusis (LASIK for hyperopia and/or hyperopic astigmatism.Methods: We prospectively evaluated 208 consecutive LASIK cases for hyperopia with or without astigmatism using the topography-guided platform of the 400 Hz Eye-Q excimer system. The mean preoperative sphere value was +3.04 ± 1.75 (range 0.75–7.25 diopters (D and the mean cylinder value was –1.24 ± 1.41 (–4.75–0 D. Flaps were created either with Intralase FS60 (AMO, Irvine, CA or FS200 (Alcon, Fort Worth, TX femtosecond lasers. Parameters evaluated included age, preoperative and postoperative refractive error, uncorrected distance visual acuity, corrected distance visual acuity, flap diameter and thickness, topographic changes, higher order aberration changes, and low contrast sensitivity. These measurements were repeated postoperatively at regular intervals for at least 24 months.Results: Two hundred and two eyes were available for follow-up at 24 months. Uncorrected distance visual acuity improved from 5.5/10 to 9.2/10. At 24 (8–37 months, 75.5% of the eyes were in the ±0.50 D range and 94.4% were in the ±1.00 D range of the refractive goal. Postoperatively, the mean sphere value was –0.39 ± 0.3 and the cylinder value was –0.35 ± 0.25. Topographic evidence showed that ablation was made in the visual axis and not in the center of the cornea, thus correlating with the angle kappa. No significant complications were encountered in this small group of patients.Conclusion: Hyperopic LASIK utilizing the topography-guided platform of the 400 Hz Eye-Q Allegretto excimer and a femtosecond laser flap appears to be safe and effective for

  15. A design of energy detector for ArF excimer lasers

    Science.gov (United States)

    Feng, Zebin; Han, Xiaoquan; Zhou, Yi; Bai, Lujun

    2017-08-01

    ArF excimer lasers with short wavelength and high photon energy are widely applied in the field of integrated circuit lithography, material processing, laser medicine, and so on. Excimer laser single pulse energy is a very important parameter in the application. In order to detect the single pulse energy on-line, one energy detector based on photodiode was designed. The signal processing circuit connected to the photodiode was designed so that the signal obtained by the photodiode was amplified and the pulse width was broadened. The amplified signal was acquired by a data acquisition card and stored in the computer for subsequent data processing. The peak of the pulse signal is used to characterize the single pulse energy of ArF excimer laser. In every condition of deferent pulse energy value levels, a series of data about laser pulses energy were acquired synchronously using the Ophir energy meter and the energy detector. A data set about the relationship between laser pulse energy and the peak of the pulse signal was acquired. Then, by using the data acquired, a model characterizing the functional relationship between the energy value and the peak value of the pulse was trained based on an algorithm of machine learning, Support Vector Regression (SVR). By using the model, the energy value can be obtained directly from the energy detector designed in this project. The result shows that the relative error between the energy obtained by the energy detector and by the Ophir energy meter is less than 2%.

  16. Comparison of femtosecond and excimer laser platforms available for corneal refractive surgery.

    Science.gov (United States)

    Chen, Lisa Y; Manche, Edward E

    2016-07-01

    The evolution of laser technology has left today's refractive surgeon with a choice between multiple laser platforms. The purpose of this review is to compare currently available femtosecond and excimer laser platforms, providing a summary of current evidence. Femtosecond lasers create LASIK flaps with better accuracy, uniformity, and predictability than mechanical microkeratomes. Newer higher-frequency femtosecond platforms elicit less inflammation, producing better visual outcomes. SMILE achieved similar safety, efficacy, and predictability as LASIK with greater preservation of corneal nerves and biomechanical strength. The emergence of wavefront technology has resulted in improved excimer laser treatments. Comparisons of wavefront-guided and wavefront-optimized treatments suggest that there is an advantage to using wavefront-guided platforms in terms of visual acuity and quality of vision. Topography-guided ablations are another well tolerated and effective option, especially in eyes with highly irregular corneas. Advances in femtosecond and excimer laser technology have not only improved the safety and efficacy of refractive procedures, but have also led to the development of promising new treatment modalities, such as SMILE and the use of wavefront-guided and topography-guided ablation. Future studies and continued technological progress will help to better define the optimal use of these treatment platforms.

  17. Excimer laser absorption on PMMA plate and on cornea: a practical approach using volume luminance

    Science.gov (United States)

    Digulescu, Petre P.; Carstocea, Benone D.; Sterian, Livia

    2001-04-01

    Excimer laser refractive surgery used in Ophthalmology in order to treat the human eye refraction problems has been performed over 10 years around the world. However a systematic approach of the physical phenomena and especially of the absorption on the cornea during the laser treatment is missing in the literature and the doctors are usually using empiric nomograms in order to achieve good results. The theoretical approach is difficult because of the complexity of the phenomena interconnected each to the others. The UV excimer laser beam used to controllably ablate the cornea is highly absorbed in the air and also is supplementary absorbed in the plume generated almost instantaneous as consequence of the ablation on the cornea. Because of this non-linear proces the energy of the laser beam delivered to the eye must be calibrated before each intervention on a patient. The purpose of the present work is to develop a mathematical model of the excimer laser absorption on PMMA and on human cornea based on a new physical notion, the Volume Luminance. The Volume Luminance is defined as volume density of the intensity of laser radiation. A brief theory of the Volume Luminance is also presented.

  18. Color-center laser spectroscopy of transient species produced by excimer-laser flash photolysis

    Energy Technology Data Exchange (ETDEWEB)

    Adams, H.; Hall, J.L.; Rusell, L.A.; Kasper, J.V.V.; Tittel, F.K.; Curl, R.F.,JR.

    1985-05-01

    Kinetic spectroscopy based on excimer-laser flash photolysis and color-center-laser (CCL) infrared probing is explored. In simiple absorption, the achievable signal-to-noise ratio (S/N) is not satisfactory even though the signal itself (corresponding to greater than 1 percent absorption) is fairly large. This is due to amplitude fluctuations of the CCL. By using a double-beam detection scheme to balance out these amplitude fluctuations the sensitivity can be improved to the extent that a 1 percent absorption gives a S/N approximately 100. In certain situations transient decreases in absorption of the precursor and transient increases in absorption due to final product formation can produce severe interferinng signals even in simple systems. This problem is overcome without a major loss in sensitivity by a recently developed 45 deg magnetic rotation scheme. These points are illustrated with spectra of Br, OH, and NH2. 21 references.

  19. Intraoperative and postoperative complications of laser in situ keratomileusis flap creation using intralase femtosecond laser and mechanical microkeratomes

    OpenAIRE

    Espandar Ladan; Meyer Jay

    2010-01-01

    An essential step of laser in situ keratomileusis surgery is corneal flap creation, Femtosecond (FS)-assisted or mechanical microkeratome. Each type has rare intraoperative and postoperative complication rates. Several recent studies have identified risk factors and guidelines to help manage these complications. Fortunately, studies have shown no loss of best-corrected visual acuity (BCVA) after the management of intraoperative and postoperative complications in IntraLase FS and mechanical mi...

  20. Corneal biomechanical effects: small-incision lenticule extraction versus femtosecond laser-assisted laser in situ keratomileusis.

    Science.gov (United States)

    Wu, Di; Wang, Yan; Zhang, Lin; Wei, Shengsheng; Tang, Xin

    2014-06-01

    To compare the biomechanical properties of the cornea after small-incision lenticule extraction (lenticule extraction group) with those after femtosecond laser-assisted laser in situ keratomileusis (femtosecond LASIK group). Tianjin Eye Hospital & Eye Institute, Tianjin Key Laboratory of Ophthalmology and Visual Science, Tianjin Medical University, Tianjin, China. Prospective comparative case series. Corneal hysteresis (CH), the corneal resistance factor (CRF), and 37 other biomechanical waveform parameters were quantitatively assessed with the Ocular Response Analyzer preoperatively and 1 week and 1, 3, and 6 months postoperatively. Each group comprised 40 eyes. The decrease in CH and the CRF was statistically significant 1 week postoperatively compared with preoperatively in both groups (Pcorneal thickness were statistically significant in the lenticule extraction group (r = 0.388 to 0.950, Pbiomechanical waveform parameters differed significantly between preoperative values and postoperative values (Pbiomechanical changes in the cornea. However, changes in the cornea's viscoelastic properties were less after lenticule extraction than after LASIK. No author has a financial or proprietary interest in any material or method mentioned. Copyright © 2014. Published by Elsevier Inc.

  1. High Efficiency Mask Based Laser Materials Processing with TEA-CO2 - and Excimer Laser

    DEFF Research Database (Denmark)

    Bastue, Jens; Olsen, Flemmming Ove

    1997-01-01

    In general, mask based laser materials processing techniques suffer from a very low energy efficiency. We have developed a simple device called an energy enhancer, which is capable of increasing the energy efficiency of typical mask based laser materials processing systems. A short review of the ...... line marking with TEA-CO2 laser of high speed canning lines. The second one is manufactured for marking or microdrilling with excimer laser.......In general, mask based laser materials processing techniques suffer from a very low energy efficiency. We have developed a simple device called an energy enhancer, which is capable of increasing the energy efficiency of typical mask based laser materials processing systems. A short review...... of the most widely used applications of these systems is given and the potential advantages of the energy enhancer are discussed.The basic principle behind the energy enhancing technique is explained and two new energy enhancers are presented and evaluated. The first one is designed especially for single text...

  2. Transformation of microcrystalline silicon films by excimer-laser-induced crystallization

    Energy Technology Data Exchange (ETDEWEB)

    Hsieh, I.-C. [Department of Electrical Engineering, Da-Yeh University, Changhua 515, Taiwan (China); Lien, S.-Y. [Department of Materials Engineering, National Chung Hsing University, 250 Kuo Kuang Rd., Taichung Taiwan 402, (China); Wuu, D.-S. [Department of Materials Engineering, National Chung Hsing University, 250 Kuo Kuang Rd., Taichung Taiwan 402 (China)]. E-mail: dsw@dragon.nchu.edu.tw

    2005-02-01

    We describe the excimer-laser-induced crystallization of microcrystalline silicon films deposited by plasma-enhanced chemical vapor deposition (PECVD). Microcrystalline silicon films containing 2 at.% hydrogen can be used as precursor films for the laser recrystallization process without a dehydrogenation step, and provide a wider laser energy fluence process window than the previous explosive recrystallization for low temperature polysilicon (poly-Si) thin-film transistor (TFT) fabrication. Ellipsometry, transmission electron microscopy (TEM), and atomic force microscopy (AFM) are used to evaluate the laser irradiated films. Specially, we describe using atomic force microscopy to obtain plane-view grain microstructure images.

  3. Corneal flap thickness and topography changes induced by flap creation during laser in situ keratomileusis.

    Science.gov (United States)

    Güell, José L; Velasco, Fortino; Roberts, Cynthia; Sisquella, Maria Teresa; Mahmoud, Ashraf

    2005-01-01

    To determine the corneal flap thickness profile produced by 3 microkeratomes and the topographic changes induced by flap creation in laser in situ keratomileusis (LASIK). Cornea and Refractive Surgery Unit, Instituto de Microcirugia Ocular de Barcelona, Autonoma University, Barcelona, Spain. In this prospective consecutive nonrandomized comparative study, patients were divided into 2 groups. In Group 1 (75 eyes), 3 microkeratomes were used: Moria LSX One, Moria M2, and Amadeus (AMO); 25 eyes per microkeratome. Pachymetry was measured with a DGH pachymeter in the center of the cornea and 3.0 mm from the center at 4 cardinal points (superior, inferior, nasal, and temporal; 3 measurements at each point) before and after the cut. The flap thickness in each sector was calculated by subtracting the mean post-flap corneal thickness from the mean pre-flap corneal thickness. In Group 2 (33 eyes), the M2 microkeratome with a 130 microm plate was used to create a superotemporal hinged flap (9 eyes) or a superonasal hinged flap (24 eyes). The topographic change induced by the microkeratome cut was evaluated using 4 sequential data acquisitions by the Keratron Scout topographic unit (Optikon) before and immediately after the cut (before laser ablation). Cardinal and oblique astigmatism and change in the axis were calculated by vectorial analysis of the simulated keratometry. Topographic Zernike analysis was performed in a subgroup. With the LSX One microkeratome, the mean flap thickness was 151.7 microm centrally, 161.9 microm superiorly, 151.4 microm inferiorly, 156.1 microm temporally, and 167.5 microm nasally. There was no statistically significant difference between the areas studied (P.05). With the Amadeus microkeratome, the mean flap thickness was 140.0 microm centrally, 152.5 superiorly, 128.5 microm inferiorly, 145.0 microm temporally, and 147.0 microm nasally. Statistically significant differences (P>.05) were found in the 4 sectors of the flap. With vectorial

  4. Application of optical tweezers and excimer laser to study protoplast fusion

    Science.gov (United States)

    Kantawang, Titirat; Samipak, Sompid; Limtrakul, Jumras; Chattham, Nattaporn

    2015-07-01

    Protoplast fusion is a physical phenomenon that two protoplasts come in contact and fuse together. Doing so, it is possible to combine specific genes from one protoplast to another during fusion such as drought resistance and disease resistance. There are a few possible methods to induce protoplast fusion, for example, electrofusion and chemical fusion. In this study, chemical fusion was performed with laser applied as an external force to enhance rate of fusion and observed under a microscope. Optical tweezers (1064 nm with 100X objective N.A. 1.3) and excimer laser (308 nm LMU-40X-UVB objective) were set with a Nikon Ti-U inverted microscope. Samples were prepared by soaking in hypertonic solution in order to induce cell plasmolysis. Elodea Canadensis and Allium cepa plasmolysed leaves were cut and observed under microscope. Concentration of solution was varied to induce difference turgor pressures on protoplasts pushing at cell wall. Free protoplasts in solution were trapped by optical tweezers to study the effect of Polyethylene glycol (PEG) solution. PEG was diluted by Ca+ solution during the process to induced protoplast cell contact and fusion. Possibility of protoplast fusion by excimer laser was investigated and found possible. Here we report a novel tool for plant cell fusion using excimer laser. Plant growth after cell fusion is currently conducted.

  5. Study on the electromagnetic radiation characteristics of discharging excimer laser system

    Science.gov (United States)

    Zhao, Duliang; Liang, Xu; Fang, Xiaodong; Wang, Qingsheng

    2016-10-01

    Excimer laser in condition of high voltage, large current and fast discharge will produce strong electromagnetic pulse radiation and electromagnetic interference on the around electrical equipment. The research on characteristics and distribution of excimer laser electromagnetic radiation could provide important basis for electromagnetic shielding and suppressing electromagnetic interference, and further improving the electromagnetic compatibility of system. Firstly, electromagnetic radiation source is analyzed according to the working principle of excimer laser. The key test points of the electromagnetic radiation, hydrogen thyratron, main discharge circuit and laser outlet, are determined by the mechanical structure and the theory of electromagnetic radiation. Secondly, characteristics of electromagnetic field were tested using a near field probe on the key positions of the vertical direction at 20, 50, and 80 cm, respectively. The main radiation frequencies and the radiation field characteristics in the near field are obtained. The experimental results show that the main radiation frequencies distribute in 47, 65, and 130 MHz for electric field and the main radiation frequencies distribute in 34, 100, and 165 MHz for magnetic field. The intensity of electromagnetic field decreases rapidly with the increase of test distance. The higher the frequency increases, the faster the amplitude attenuate. Finally, several electromagnetic interference suppression measurement methods are proposed from the perspective of electromagnetic compatibility according to the test results.

  6. Cox proportional hazards model of myopic regression for laser in situ keratomileusis flap creation with a femtosecond laser and with a mechanical microkeratome.

    Science.gov (United States)

    Lin, Meng-Yin; Chang, David C K; Hsu, Wen-Ming; Wang, I-Jong

    2012-06-01

    To compare predictive factors for postoperative myopic regression between laser in situ keratomileusis (LASIK) with a femtosecond laser and LASIK with a mechanical microkeratome. Nobel Eye Clinic, Taipei, Taiwan. Retrospective comparative study. Refractive outcomes were recorded 1 day, 1 week, and 1, 3, 6, 9, and 12 months after LASIK. A Cox proportional hazards model was used to evaluate the impact of the 2 flap-creating methods and other covariates on postoperative myopic regression. The femtosecond group comprised 409 eyes and the mechanical microkeratome group, 377 eyes. For both methods, significant predictors for myopic regression after LASIK included preoperative manifest spherical equivalent (P=.0001) and central corneal thickness (P=.027). Laser in situ keratomileusis with a mechanical microkeratome had a higher probability of postoperative myopic regression than LASIK with a femtosecond laser (P=.0002). After adjusting for other covariates in the Cox proportional hazards model, the cumulative risk for myopic regression with a mechanical microkeratome was higher than with a femtosecond laser 12 months postoperatively (P=.0002). With the definition of myopic regression as a myopic shift of 0.50 diopter (D) or more and residual myopia of -0.50 D or less, the risk estimate based on the mean covariates in all eyes in the femtosecond group and mechanical microkeratome group at 12 months was 43.6% and 66.9%, respectively. Laser in situ keratomileusis with a mechanical microkeratome had a higher risk for myopic regression than LASIK with a femtosecond laser through 12 months postoperatively. Copyright © 2012. Published by Elsevier Inc.

  7. Corneal Clarity and Visual Outcomes after Small-Incision Lenticule Extraction and Comparison to Femtosecond Laser-Assisted In Situ Keratomileusis.

    Science.gov (United States)

    Lazaridis, Apostolos; Droutsas, Konstantinos; Sekundo, Walter; Petrak, Michael; Schulze, Stephan

    2017-01-01

    Purpose. To evaluate corneal clarity and visual outcomes after small-incision lenticule extraction (SMILE) and compare them to femtosecond laser-assisted in situ keratomileusis (FS-LASIK). Materials and Methods. Fifty-eight myopic eyes of 33 patients who underwent SMILE were compared to 58 eyes of 33 patients treated with FS-LASIK. All procedures were performed using VisuMax® femtosecond laser and MEL 80® excimer laser (Carl Zeiss Meditec AG, Germany). Pentacam™ (Oculus, Germany) was used for pre- and 3-month postoperative corneal densitometry (CD) analysis. CD was evaluated at 3 optically relevant, concentric radial zones (0-2 mm, 2-6 mm, and 0-6 mm annulus) around the corneal apex and at 3 different anatomical corneal layers (anterior, central, and posterior). Associations of postoperative CD values with the lenticule thickness and ablation depth were examined. Preoperative and postoperative corrected distance visual acuity (CDVA) values were also compared. Results. After SMILE, the total CD (all corneal layers) at 0-6 mm annulus showed no significant change compared to preoperative values (P = 0.259). After FS-LASIK, the total CD was significantly reduced (P = 0.033). Three-month postoperative CD showed no significant differences between the 2 groups for all examined annuli (0-2 mm: P = 0.569; 2-6 mm: P = 0.055; and 0-6 mm: P = 0.686). Total CD after SMILE at 0-6 mm annulus displayed a weak negative association with the lenticule thickness (P = 0.079, R2 = 0.0532) and after FS-LASIK displayed a weak negative association with the ablation depth (P = 0.731, R2 = 0.0015). Postoperative CDVA was similar for both groups (P = 0.517). Conclusion. Quantification of corneal clarity using the Scheimpflug CD showed similar results before and 3 months after SMILE. Compared to FS-LASIK, no significant differences of corneal clarity and CDVA were found 3 months postoperatively.

  8. Laser in-situ keratomileusis in patients with diabetes mellitus: a review of the literature

    Directory of Open Access Journals (Sweden)

    Simpson RG

    2012-10-01

    Full Text Available Rachel G Simpson,1 Majid Moshirfar,2 Jason N Edmonds,2 Steven M Christiansen21University of Arizona College of Medicine, Phoenix, AZ; 2Moran Eye Center, University of Utah School of Medicine, Salt Lake City, UT, USAPurpose: A growing number of diabetic patients request laser in situ keratomileusis (LASIK for elective vision correction each year. While the United States Food and Drug Administration considers diabetes a relative contraindication to LASIK surgery, there are several reports in the literature of LASIK being performed safely in this patient population. The purpose of this review was to examine whether diabetes should still be considered a contraindication to LASIK surgery by reviewing the ocular and systemic complications of diabetes, and examining the existing data on the outcomes of LASIK in diabetic patients.Methods: A literature review was conducted through PubMed, Medline, and Ovid to identify any study on LASIK surgery in patients with diabetes mellitus. This search was conducted without date restrictions. The search used the Medical Subject Headings (MeSH® term LASIK linked by the word “and” to the following MeSH and natural language terms: diabetes, diabetes mellitus, systemic disease, and contraindications. Abstracts for all studies meeting initial search criteria were reviewed for relevance. There were no prospective clinical studies identified. Three retrospective studies were identified. Key sources from these papers were identified, reviewed, and included as appropriate. An additional literature search was conducted to identify any study of ocular surgery on patients with diabetes using the MeSH terms refractive surgery, photorefractive keratectomy, radial keratotomy, cataract surgery, vitrectomy, and iridectomy linked by the word “and” to the following MeSH terms: diabetes, diabetes mellitus, and systemic disease. This search was conducted without date restrictions. Abstracts of studies meeting the initial

  9. Accuracy of refractive outcomes in myopic and hyperopic laser in situ keratomileusis: Manifest versus aberrometric refraction.

    Science.gov (United States)

    Reinstein, Dan Z; Morral, Merce; Gobbe, Marine; Archer, Timothy J

    2012-11-01

    To compare the achieved refractive accuracy of laser in situ keratomileusis (LASIK) performed based on manifest refraction with the predicted accuracy that would have been achieved using WASCA aberrometric refraction with and without Seidel correction factor for sphere. London Vision Clinic, London, United Kingdom. Comparative case series. Myopic eyes and hyperopic eyes had LASIK based on manifest refraction. Two aberrometric refractions were obtained preoperatively: Seidel, which includes spherical aberration in the sphere calculation, and non-Seidel. Bland-Altman plots were used to show the agreement between aberrometric and manifest refractions. Predicted LASIK outcomes had aberrometric refraction been used were modeled by shifting the postoperative manifest refraction by the vector difference between the preoperative manifest and aberrometric refractions. This study included 869 myopic eyes and 413 hyperopic eyes. The mean differences (manifest minus aberrometric) in spherical equivalent were +0.03 diopters (D) ± 0.48 (SD) (Seidel aberrometric) and +0.45 ± 0.42 D (non-Seidel aberrometric) for myopia and -0.20 ± 0.39 D and +0.39 ± 0.34 D, respectively, for hyperopia. The mean differences in cylinder magnitude were -0.10 ± 0.27 D and 0.00 ± 0.25 D, respectively. The percentage of eyes within ±0.50 D of the attempted correction was 81% (manifest), 70% (Seidel), and 67% (non-Seidel) for myopia and 71% (manifest), 61% (Seidel), and 64% (non-Seidel) for hyperopia. The achieved refractive accuracy by manifest refraction was better than the predicted accuracy had Seidel or non-Seidel aberrometric refractions been used for surgical planning. Using the Seidel method improved the accuracy in myopic eyes but not in hyperopic eyes. Dr. Reinstein is a consultant to Carl Zeiss Meditec AG and has a proprietary interest in the Artemis technology (Arcscan Inc., Morrison, Colorado, USA) through patents administered by the Cornell Center for Technology Enterprise and

  10. [Comparison of corneal wound healing of photorefractive keratectomy and laser in situ keratomileusis in rabbits].

    Science.gov (United States)

    Ma, Xiao-Hua; Li, Jing-Hai; Bi, Hong-Sheng; Zhou, Fang; Li, Yan

    2003-03-01

    To compare effects of photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) on the cornea and corneal wound healing and to investigate the possible mechanism of corneal haze and myopic regression histopathologically. Twenty-four New Zealand white rabbits were allocated randomly to correct -4.00 and -8.00 diopters and were operated with PRK on right eyes and LASIK on left eyes. At 10 days and 1, 3, and 6 months, corneal haze was observed, refraction was evaluated, and 3 rabbits were randomly selected for each time point to be enucleated, and corneas to be bisected. One half of each cornea was evaluated using transmission electron microscopy, and the other half was evaluated using either light microscopy or immunohistochemical staining for collagen type III, IV, fibronectin (FN) and transforming growth factor-beta(1) (TGF-beta(1)). Different degrees of corneal haze and myopic regression were observed after PRK: the higher the desired myopic correction, the heavier the haze. Corneal wound healing response was greater and lasted longer after PRK than after LASIK. Various pathological findings such as epithelial hyperplasia, basal membrane reforming and extracellular matrix deposits were found in the ablation zone and repair mechanisms were still active at 6 months after PRK. Whereas after LASIK, the interface between the flap and stromal bed was transparent except for growing epithelial plugs and lightly proliferating stroma coinciding with the flap margins. After both PRK and LASIK, all corneal cell types were consistently positive for TGF-beta(1) antibody during the corneal wound healing time. TGF-beta(1) antibody positivity decreased as the wound healing approached completion. The histopathological changes of corneal haze and myopic regression are as follows: epithelial hyperplasia, basal membrane immaturity, anterior stromal keratocyte increase and activity, new collagen III production and irregular arrangement thereof, and FN deposition in the

  11. Excimer laser refractive surgery versus phakic intraocular lenses for the correction of moderate to high myopia.

    Science.gov (United States)

    Barsam, Allon; Allan, Bruce D S

    2014-06-17

    Myopia is a condition in which the focusing power (refraction) of the eye is greater than that required for clear distance vision. There are two main types of surgical correction for moderate to high myopia; excimer laser and phakic intraocular lenses (IOLs). Excimer laser refractive surgery for myopia works by removing corneal stroma to lessen the refractive power of the cornea and to bring the image of a viewed object into focus onto the retina rather than in front of it. Phakic IOLs for the treatment of myopia work by diverging light rays so that the image of a viewed object is brought into focus onto the retina rather than in front of the retina. They can be placed either in the anterior chamber of the eye in front of the iris or in the posterior chamber of the eye between the iris and the natural lens. To compare excimer laser refractive surgery and phakic IOLs for the correction of moderate to high myopia by evaluating postoperative uncorrected visual acuity, refractive outcome, potential loss of best spectacle corrected visual acuity (BSCVA) and the incidence of adverse outcomes. We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (2014, Issue 1), Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE (January 1946 to February 2014), EMBASE (January 1980 to February 2014), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), ClinicalTrials.gov (www.clinicaltrials.gov) and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 11 February 2014. We included randomised controlled trials (RCTs) comparing excimer laser refractive surgery and phakic IOLs for the correction of myopia greater than 6.0 diopters (D) spherical equivalent. Two authors independently

  12. Combined application of prophylactic corneal cross-linking and laser in-situ keratomileusis - a review of literature.

    Science.gov (United States)

    Chan, Tommy C Y; Ng, Alex L K; Chan, Karen K W; Cheng, George P M; Wong, Ian Y H; Jhanji, Vishal

    2017-11-01

    Laser in-situ keratomileusis (LASIK) is safe and effective laser refractive procedures in treating refractive errors. However, regression of treatment and iatrogenic keratectasia remain to be a major concern, especially in treating thin cornea with high ametropia. Collagen cross-linking (CXL) is an effective method in stopping keratoconus progression through increasing the biomechanical strength of the cornea. Adjuvant cross-linking to refractive procedures can theoretically help prevent regression and reduce the risk of keratectasia development by increasing the mechanical stability of cornea. During the procedure, riboflavin is directly applied to the corneal stroma, thereby reducing the need of de-epithelialization as in the conventional protocol for keratoconus. Currently, there is still no consensus regarding the indication of CXL during refractive procedure, nor any standardized treatment protocol. This article aims to summarize the current evidence regarding the use of adjuvant CXL in LASIK. © 2016 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

  13. Discharge instabilities in high-pressure fluorine based excimer laser gas mixtures

    OpenAIRE

    Mathew, D

    2007-01-01

    Fluorine based excimer lasers such as KrF, ArF and F2 are currently the most powerful sources available in the ultraviolet wavelength range, operating at 248 nm, at 193 nm and at 157 nm, respectively. They are thus of central importance for numerous applications in this range. At these short wavelengths, reaching the laser threshold for an efficient operation, F2-based lasers require to be pumped, in a controlled manner, with very high power densities. This can practically be achieved only vi...

  14. Excimer Laser Phototherapeutic Keratectomy for the Treatment of Clinically Presumed Fungal Keratitis

    OpenAIRE

    Liang-Mao Li; Li-Quan Zhao; Ling-Hui Qu; Peng Li

    2014-01-01

    This retrospective study was to evaluate treatment outcomes of excimer laser phototherapeutic keratectomy (PTK) for clinically presumed fungal keratitis. Forty-seven eyes of 47 consecutive patients underwent manual superficial debridement and PTK. All corneal lesions were located in the anterior stroma and were resistant to medication therapy for at least one week. Data were collected by a retrospective chart review with at least six months of follow-up data available. After PTK, infected cor...

  15. Electron microscopic and immunohistochemical examination of scarred human cornea re-treated by excimer laser.

    Science.gov (United States)

    Bleckmann, Heinrich; Schnoy, Norbert; Kresse, Hans

    2002-04-01

    To elucidate differences, at the macromolecular level, in corneal tissue subjected to repeated argon fluoride excimer treatment. A light microscopic, electron microscopic, and immunohistochemical study was performed on a scarred human cornea. Keratocytes were enlarged with an expanded endoplasmic reticulum and exhibited a fibroblastic appearance. Amorphous material was observed extracellularly. Collagen fibrils exhibited a disordered arrangement while banding patterns and diameter were normal. Immunohistochemical investigation of several collagen types, of collagen-associated proteoglycans, and of basement membrane components demonstrated an enhanced immunoreactivity of all of them in the scarred area. Type V collagen was found as a normal component of the epithelial basement membrane whereas types I and III collagen were present beneath Bowman's layer. Excimer-laser-treated sections revealed considerably stronger subepithelial staining for collagen types I, III, IV, and V. Laminin-1, a typical component of basement membranes, was detectable throughout the scarred tissue. The small proteoglycans decorin and fibromodulin accumulated in a patch-like manner in the scarred tissue below the epithelium, whereas biglycan was expressed by the epithelium and throughout the stroma. Lumican was expressed most strongly by the epithelium and rather equally distributed in the excimer-laser-treated and in the normal stroma. Effects of argon laser treatment of the cornea must be regarded as a process acting over many months. Intra- and extracellular structures and components are involved and influence the unpredictable shape of the corneal architecture.

  16. Comparison of dry-eye disease after the femtosecond laser and mechanical microkeratome for laser in situ keratomileusis

    Directory of Open Access Journals (Sweden)

    Meng-Jun Fu

    2015-02-01

    Full Text Available AIM: To analyze dryeye disease after the femtosecond laser and mechanical microkeratome for laser in situ keratomileusis(LASIKby Oculus dry eye analyzer examination.METHODS: The people who had femtosecond LASIK(FS-LASIKand mechanical microkeratome LASIK in Weifang Eye Hospital from January 2014 to April 2014 were observed. Sixty patients(120 eyeswho had corneal refractive surgery were collected. The average age of patients was 27.46±6.65 years old. The LASIK group had 28 patients(56 eyesand the FS-LASIK group had 32 patients(64 eyes. The tears river altitude, first tear break up time(BUT, and average BUT at preoperative, 1wk and 1mo after operation were observed by Oculus dry eye analyzer.RESULTS: By Oculus dry eye analyzer examination, the preoperative tears river altitude of patients was 0.25±0.10mm. First BUT was 6.70±3.86s. Average BUT time was 10.14±4.51s. At 1wk after operation, the tears river altitude of patients was 0.19±0.04mm. The first BUT time was 4.87±1.71s. The average BUT time was 7.77±2.30s. There was significant difference between preoperative and 1wk after operation(PPPCONCLUSION: LASIK and FS-LASIK patients have different degree of dry eye symptom after operation. Dry eye symptoms mainly display in the decrease of tear production and the stability of tear film. It will be better after giving artificial tears. Oculus dry eye analyzer is a non-invasive examination equipment. It can reflect the amount of tears and the stability of tear film. It is usefull in rapid diagnosis of dry eye and judgment of the degree of dry eye symptom after LASIK operation.

  17. Comparison of KrF and ArF excimer laser treatment of biopolymer surface

    Energy Technology Data Exchange (ETDEWEB)

    Michaljaničová, I. [Department of Solid State Engineering, University of Chemistry and Technology, 166 28 Prague (Czech Republic); Slepička, P., E-mail: petr.slepicka@vscht.cz [Department of Solid State Engineering, University of Chemistry and Technology, 166 28 Prague (Czech Republic); Heitz, J.; Barb, R.A. [Institute of Applied Physics, Johannes Kepler University Linz, A-4040 Linz (Austria); Sajdl, P. [Department of Power Engineering, University of Chemistry and Technology, 166 28 Prague (Czech Republic); Švorčík, V. [Department of Solid State Engineering, University of Chemistry and Technology, 166 28 Prague (Czech Republic)

    2015-06-01

    Highlights: • The influence of ArF and KrF laser on biopolymer surface was determined. • ArF laser acts predominantly on biopolymer surface. • PHB roughness is increased similarly for both applied wavelengths. • Roughness of nanostructures can be precisely controlled. • ArF laser introduces nitrogen on PHB surface. - Abstract: The goal of this work was the investigation of the impact of two different excimer lasers on two biocompatible and biodegradable polymers (poly-L-lactide and poly hydroxybutyrate). Both polymers find usage in medical and pharmaceutical fields. The polymers were modified by KrF and ArF excimer lasers. Subsequently the impact on surface morphology, surface chemistry changes, and thermal properties was studied by means of confocal and AFM microscopy, FTIR and XPS spectroscopy and DSC calorimetry. Under the same conditions of laser treatment it was observed that ArF laser causes more significant changes on surface chemistry, surface morphology and pattern formation on the polymers under investigation. The data obtained in this work can be used for a wide range of possible applications, in tissue engineering or in combination with metallization in electronics, e.g. for biosensors.

  18. Surface ablation of PLLA induced by KrF excimer laser

    Energy Technology Data Exchange (ETDEWEB)

    Slepička, P., E-mail: petr.slepicka@vscht.cz [Department of Solid State Engineering, Institute of Chemical Technology Prague, 166 28 Prague (Czech Republic); Michaljaničová, I. [Department of Solid State Engineering, Institute of Chemical Technology Prague, 166 28 Prague (Czech Republic); Sajdl, P. [Department of Power Engineering, Institute of Chemical Technology, 166 28 Prague (Czech Republic); Fitl, P. [Department of Physics and Measurements, Faculty of Chemical Engineering, Institute of Chemical Technology Prague, 166 28 Prague (Czech Republic); Švorčík, V. [Department of Solid State Engineering, Institute of Chemical Technology Prague, 166 28 Prague (Czech Republic)

    2013-10-15

    The surface characterization of PLLA (poly-L-lactic-acid) and its ablation due to excimer laser treatment is introduced in this paper. The main focus is to determine surface wettability and morphology changes in combination with changes of surface chemistry. The ablation loss and the determination of ablation threshold were used to study the biopolymer stability when treated to different laser fluences and pulse counts. The surface polarity was estimated using goniometry. AFM (atomic force microscopy) was used to determine the polymer surface morphology and roughness. The excimer laser has a strong effect on the polymer ablation. The thickness loss is strongly dependent on the laser fluence and number of pulses. For the fluences up to 30 mJ cm{sup −2} and 6000 pulses achieved ablation about 5 μm. The glass transition temperature and melting point were determined for the pristine and laser treated films. The increasing pulsed laser fluence leads to the major changes in roughness and morphology. The surface chemistry depends strongly on number of laser pulses.

  19. [Retinal detachment after Excimer laser (myopic LASIK or PRK). A retrospective multicentric study: 15 cases].

    Science.gov (United States)

    Feki, J; Trigui, A; Chaabouni, M; Ben Salah, S; Bouacida, B; Chechia, N; Zayani, A; Nouira, F; Daghfous, F; Ayed, S; Kamoun, M

    2005-05-01

    Refractive surgery by LASIK or photorefractive keratectomy (PRK) generaly aims at a myopic population that has a high probability of developing rhegmatogenous retinal detachment (RD). The authors report a multicenter study with 15 cases of RD appearing after refractive surgery by Excimer laser and discuss the role played by the techniques used. Five centers fitted with nine Excimer laser devices took part in this study. Of 22,700 eyes undergoing refractive myopic surgery during the period 1994-2002, 15 eyes developed rhegmatogenous RD. The average age of the patients with RD was 37 years. The average myopia was 13.5 D. RD occurred a mean of 20 months after refractive laser. Fifteen eyes of 13 patients developed a rhegmatogenous RD, two of which were bilateral. Eight of these cases had LASIK surgery and six had photorefractive keratectomy; one of the latter patients was retreated with LASIK because of substantial regression after PRK. RD was total or subtotal in five eyes, partial superior with a temporal tear in six eyes, and nasal in three eyes. One case with inferior RD, two cases with giant retinal tear and one case with posterior tear were also repaired. Fourteen eyes were suitable for operation. The retina was reattached in 12 cases. Mean postoperative visual acuity was 7/10. The occurrence of rhegmatogenous RD in the myopic population is estimated at 2.2%. It is estimated at 0.1% in the emmetropic population. The Excimer laser, through its thermic effects, shock wave, traumatism undergone by the suction ring at the time of LASIK surgery, could increase this risk in myopic patients. A review of the literature cast doubt on the cause and effect hypothesis. Personal and multicenter studies (including ours) show that the frequency rate of rhegmatogenous RD after Excimer laser is equivalent and even lower than that estimated with an emmetropic population. The low percentage of RD after Excimer surgery found in the literature as well as in our study (surgery, the

  20. Small incision lenticule extraction (SMILE) versus laser in-situ keratomileusis (LASIK): study protocol for a randomized, non-inferiority trial

    OpenAIRE

    Ang Marcus; Tan Donald; Mehta Jodhbir S

    2012-01-01

    Abstract Background Small incision lenticule extraction or SMILE is a novel form of ‘flapless’ corneal refractive surgery that was adapted from refractive lenticule extraction (ReLEx). SMILE uses only one femtosecond laser to complete the refractive surgery, potentially reducing surgical time, side effects, and cost. If successful, SMILE could potentially replace the current, widely practiced laser in-situ keratomileusis or LASIK. The aim of this study is to evaluate whether SMILE is non-infe...

  1. Fabrication of SERS Active Surface on Polyimide Sample by Excimer Laser Irradiation

    Directory of Open Access Journals (Sweden)

    T. Csizmadia

    2014-01-01

    Full Text Available A possible application of excimer laser irradiation for the preparation of surface enhanced Raman spectroscopy (SERS substrate is demonstrated. A polyimide foil of 125 μm thickness was irradiated by 240 pulses of focused ArF excimer laser beam (λ = 193 nm, FWHM = 20 ns. The applied fluence was varied between 40 and 80 mJ/cm2. After laser processing, the sample was coated with 40 nm silver by PLD in order to create a conducting layer required for the SERS application. The SERS activity of the samples was tested by Raman microscopy. The Raman spectra of Rhodamine 6G aqueous solution (c=10−3 mol/dm3 were collected from the patterned and metalized areas. For areas prepared at 40–60 mJ/cm2 laser fluences, the measured Raman intensities have shown a linear dependence on the applied laser fluence, while above 60 mJ/cm2 saturation was observed. The morphology of the SERS active surface areas was investigated by scanning electron microscopy. Finite element modeling was performed in order to simulate the laser-absorption induced heating of the polyimide foil. The simulation resulted in the temporal and spatial distribution of the estimated temperature in the irradiated polyimide sample, which are important for understanding the structure formation process.

  2. The development and progress of XeCl Excimer laser system

    Science.gov (United States)

    Zhang, Yongsheng; Ma, Lianying; Wang, Dahui; Zhao, Xueqing; Zhu, Yongxiang; Hu, Yun; Qian, Hang; Shao, Bibo; Yi, Aiping; Liu, Jingru

    2015-05-01

    A large angularly multiplexed XeCl Excimer laser system is under development at the Northwest Institute of Nuclear Technology (NINT). It is designed to explore the technical issues of uniform and controllable target illumination. Short wavelength, uniform and controllable target illumination is the fundamental requirement of high energy density physics research using large laser facility. With broadband, extended light source and multi-beam overlapping techniques, rare gas halide Excimer laser facility will provide uniform target illumination theoretically. Angular multiplexing and image relay techniques are briefly reviewed and some of the limitations are examined to put it more practical. The system consists of a commercial oscillator front end, three gas discharge amplifiers, two electron beam pumped amplifiers and the optics required to relay, encode and decode the laser beam. An 18 lens array targeting optics direct and focus the laser in the vacuum target chamber. The system is operational and currently undergoing tests. The total 18 beams output energy is more than 100J and the pulse width is 7ns (FWHM), the intensities on the target will exceed 1013W/cm2. The aberration of off-axis imaging optics at main amplifier should be minimized to improve the final image quality at the target. Automatic computer controlled alignment of the whole system is vital to efficiency and stability of the laser system, an array of automatic alignment model is under test and will be incorporated in the system soon.

  3. Green synthesis of selenium nanoparticles by excimer pulsed laser ablation in water

    Directory of Open Access Journals (Sweden)

    O. Van Overschelde

    2013-10-01

    Full Text Available Pure selenium nanoparticles were successfully synthesized by Liquid Phase - Pulsed Laser Ablation (LP-PLA in de-ionized water. Excimer laser (248 nm operating at low fluence (F ∼ 1 J/cm2 was used to generate colloidal solutions of selenium nanoparticles. The obtained selenium nanoparticles were characterized by UV-visible spectroscopy, Raman spectroscopy, Dynamic Light Scattering, and Transmission Electron Microscopy. We describe the multi-modal size distributions generated and use the centrifugation method to isolate the smallest nanoparticles (∼60 nm in diameter.

  4. Management of slipped laser in situ keratomileusis flap following intrastromal corneal ring implantation in post-LASIK ectasia.

    Science.gov (United States)

    Abad, Juan-Carlos

    2008-12-01

    Two cases of intrastromal corneal ring (Intacs, Addition Technology) implantation to treat post-laser in situ keratomileusis (LASIK) ectasia developed progressive slippage of the flap over the stromal bed, resulting in progressive flattening of the affected meridian. The flattening was thought to have occurred because the poorly healed flap edge could not withstand the change in corneal shape induced by the ring segments. The flap was lifted, debris was removed, and the flap was sutured to the residual stromal bed using interrupted 10-0 nylon sutures passed through two thirds of the cornea. The sutures induced a localized area of scarring that acted as "welding spots" and prevented further flap slippage. Refractive stability after suture removal supports the hypothesis that a sutured flap restores (at least partially) the biomechanical strength of post-LASIK corneas.

  5. Prospective, randomized, contralateral eye comparison of tetracaine and proparacaine for pain control in laser in situ keratomileusis and photorefractive keratectomy

    Directory of Open Access Journals (Sweden)

    Moshirfar M

    2014-06-01

    Full Text Available Majid Moshirfar,1 Mark D Mifflin,1 Michael V McCaughey,2 Adam J Gess1 1John A Moran Eye Center, University of Utah, Salt Lake City, UT, USA; 2University of New Mexico School of Medicine, Albuquerque, NM, USA Background: Tetracaine and proparacaine are two of the most commonly used medications for providing topical anesthesia in laser in situ keratomileusis (LASIK and photorefractive keratectomy (PRK. These agents have not been previously compared in a prospective manner to determine their efficacy in these settings. Methods: This prospective, single-masked, randomized study comprised 256 eyes from 128 consecutive patients being treated with LASIK or PRK who were randomized to receive tetracaine in one eye and proparacaine in the other. The patients were blinded as to which anesthetic agent was used in each eye. Pain levels were graded on a 0–10 scale, and were assessed upon instillation, during surgery, immediately postoperatively, 30 minutes postoperatively, overnight, and on postoperative day 1. Patients were asked 30 minutes after surgery which anesthetic agent they would choose. Results: Both anesthetic agents resulted in diminished amounts of subjective pain in patients undergoing LASIK and PRK. Tetracaine caused significantly more pain upon instillation than proparacaine for both LASIK and PRK patients. LASIK patients noted significantly less pain 30 minutes after surgery when treated with tetracaine. Significantly more LASIK patients preferred the eye treated with tetracaine. These differences were not present in the PRK group. Conclusion: Both tetracaine and proparacaine are effective methods of topical anesthesia in LASIK and PRK. Tetracaine caused significantly more pain upon instillation in all patients, but resulted in greater analgesia 30 minutes after surgery in the LASIK group. Patients in the LASIK group expressed a preference for tetracaine over proparacaine. There was no significant drop preference among PRK patients

  6. Effects of excimer laser annealing on low-temperature solution based indium-zinc-oxide thin film transistor fabrication

    OpenAIRE

    Chen,Chao-Nan; Huang, Jung-Jie

    2015-01-01

    A Solution Based Indium-Zinc-Oxide thin-film transistor (TFT) with a field-effect mobility of 0.58 cm2/Vs, a threshold voltage of 2.84 V by using pulse laser annealing processes. Indium-zinc-oxide (IZO) films with a low process temperature were deposited by sol-gel solution based method and KrF excimer laser annealing (wavelength of 248 nm). Solution based indium-zinc-oxide (IZO) films usually needs high temperature about 500 °C post annealing in a oven. KrF excimer laser annealing shows adva...

  7. XeCl excimer laser with new prism resonator configurations and its performance characteristics.

    Science.gov (United States)

    Benerji, N S; Singh, A; Varshnay, N; Singh, Bijendra

    2015-07-01

    New resonator cavity configurations, namely, the prism resonator and unstable prism resonator, are demonstrated for the first time in an excimer (XeCl) laser with interesting and novel results. High misalignment tolerance ∼50 mrad is achieved with considerably reduced beam divergence of less than ∼1 mrad without reduction in output power capabilities of the laser. The misalignment tolerance of ∼50 mrad is a dramatic improvement of ∼25 times compared to ∼2 mrad normally observed in standard excimer laser with plane-plane cavity. Increase in depth of focus from 3 mm to 5.5 mm was also achieved in case of prism resonator configuration with an improvement of about 60%. Unstable prism resonator configuration is demonstrated here in this paper with further reduction in beam divergence to about 0.5 mrad using plano-convex lens as output coupler. The misalignment tolerance in case of unstable prism resonator was retained at about 30 mrad which is a high value compared to standard unstable resonators. The output beam spot was completely filled with flat-top profile with prism resonator configurations, which is desired for various material processing applications. Focusing properties and beam divergence in case of prism resonator have been investigated using SEM (scanning electron microscope) images. SEM images of the focused spot size (∼20 μm holes) on metal sheet indicate beam divergence of about 0.05 mrad which is about 1.5 times diffraction limit. Energy contained in this angle is thus sufficient for micro-machining applications. Clean and sharp edges of the micro-holes show high pointing stability with multiple shot exposures. Such characteristics of the excimer laser system will be extremely useful in micro-machining and other field applications.

  8. XeCl excimer laser with new prism resonator configurations and its performance characteristics

    Energy Technology Data Exchange (ETDEWEB)

    Benerji, N. S., E-mail: nsb@rrcat.gov.in, E-mail: bsingh@rrcat.gov.in; Singh, A.; Varshnay, N.; Singh, Bijendra, E-mail: nsb@rrcat.gov.in, E-mail: bsingh@rrcat.gov.in [Excimer Laser Section, LMPD, Raja Ramanna Center for Advanced Technology, Indore 452013 (India)

    2015-07-15

    New resonator cavity configurations, namely, the prism resonator and unstable prism resonator, are demonstrated for the first time in an excimer (XeCl) laser with interesting and novel results. High misalignment tolerance ∼50 mrad is achieved with considerably reduced beam divergence of less than ∼1 mrad without reduction in output power capabilities of the laser. The misalignment tolerance of ∼50 mrad is a dramatic improvement of ∼25 times compared to ∼2 mrad normally observed in standard excimer laser with plane-plane cavity. Increase in depth of focus from 3 mm to 5.5 mm was also achieved in case of prism resonator configuration with an improvement of about 60%. Unstable prism resonator configuration is demonstrated here in this paper with further reduction in beam divergence to about 0.5 mrad using plano-convex lens as output coupler. The misalignment tolerance in case of unstable prism resonator was retained at about 30 mrad which is a high value compared to standard unstable resonators. The output beam spot was completely filled with flat-top profile with prism resonator configurations, which is desired for various material processing applications. Focusing properties and beam divergence in case of prism resonator have been investigated using SEM (scanning electron microscope) images. SEM images of the focused spot size (∼20 μm holes) on metal sheet indicate beam divergence of about 0.05 mrad which is about 1.5 times diffraction limit. Energy contained in this angle is thus sufficient for micro-machining applications. Clean and sharp edges of the micro-holes show high pointing stability with multiple shot exposures. Such characteristics of the excimer laser system will be extremely useful in micro-machining and other field applications.

  9. Reconsidering Sequential Double Running Suture Removal After Penetrating Keratoplasty: A Prospective Randomized Study Comparing Excimer Laser and Motor Trephination.

    Science.gov (United States)

    Seitz, Berthold; Hager, Tobias; Langenbucher, Achim; Naumann, Gottfried O H

    2017-12-14

    We assessed the impact of sequential double running suture removal on corneal curvature after penetrating keratoplasty (PK), comparing mechanical and nonmechanical excimer laser trephination. PK was performed in 134 patients (mean age 51 ± 18 yrs) using either the excimer laser [excimer, n = 60 (37 keratoconus and 23 Fuchs dystrophy)] or motor trephination [control, n = 74 (44 keratoconus and 30 Fuchs dystrophy)] and a double running cross-stitch suture. Refractometry, Zeiss keratometry, and Tomey corneal topography were performed before removal of the first suture (15.2 ± 4.2 mo) and immediately before and at least 6 weeks after removal of the second suture (21.4 ± 5.6 mo). Keratometry before removal of the first (-1.7 ± 2.3 D vs. -3.1 ± 2.8 D) and second (-2.3 ± 2.6 D vs. -3.8 ± 2.8 D) sutures showed that the change in the corneal base curve was significantly smaller in the excimer group than the control group (P control groups, respectively, resulting in significantly lower astigmatism in the excimer (3.1 ± 2.1 D) group compared with the control group (6.2 ± 2.9 D) with "all-sutures-out" (P vector-corrected astigmatism (Jaffe) was significantly smaller in the excimer group (4.3 ± 3.5 D) than in the control group (6.9 ± 4.5 D; P motor trephination.

  10. Plume emission, shock wave and surface wave formation during excimer laser ablation of the cornea.

    Science.gov (United States)

    Bor, Z; Hopp, B; Rácz, B; Szabó, G; Ratkay, I; Süveges, I; Füst, A; Mohay, J

    1993-01-01

    Excimer lasers are now used for corneal surgery; however, the physical processes occurring during photoablation of the cornea are incompletely understood. High speed laser-based photographic arrangement was constructed. The temporal resolution was better than 1 ns. The setup could work as a Schlieren arrangement, which is sensitive to the refractive index change caused by the shock wave propagating in the air above the eye. With minor changes the setup was converted into a shadowgraph, which could detect the ablation plume and the waves propagating on the surface of the eye. Due to the impact of the excimer laser pulse onto the surface of the cornea, a shock wave was generated in the air. The shadowgraph clearly showed the ejection of the ablated cornea. The ejection velocity of the plume was found to be over 600 m/s. It was shown for the first time that the recoil forces of the plume are generating a wave on the surface of the eye. The laser-based high speed photographic arrangement is a powerful arrangement in the study of physical effects occurring during photoablation of the cornea.

  11. Changes in gene expression by 193- and 248-nm excimer laser radiation in cultured human fibroblasts.

    Science.gov (United States)

    Rimoldi, D; Flessate, D M; Samid, D

    1992-09-01

    Tissue ablation by ultraviolet excimer lasers results in exposure of viable cells to subablative doses of radiation. To understand the potential biological consequences better, we have studied changes in gene expression in cultured human skin fibroblasts exposed to either 193- or 248-nm laser light. Northern blot analyses revealed that both treatments up-regulate a common set of genes, including interstitial collagenase, tissue inhibitor of metalloprotease, metallothionein, and the proto-oncogene c-fos. Dose-response and kinetic studies of collagenase induction by 193-nm radiation showed a maximal effect with 60 J/m2 and at approximately 24 h. The induction was still persistent 96 h later. In addition to the commonly affected genes, known to be activated also by conventional UV light (254 nm) and tumor-promoting phorbol esters, other genes were found to be selectively induced by the 193-nm radiation. The heat-shock hsp70 mRNA, undetectable in controls and in cultures irradiated at 248 nm, was transiently induced 8 h after exposure to 193-nm radiation. Furthermore, a selective up-regulation of collagen type I expression was observed. The results indicate that the 193- and 248-nm radiations by excimer lasers elicit specific and different cellular responses, in addition to an overlapping pathway of gene activation common also to UV radiation by germicidal lamps. The laser-induced genes could serve as molecular markers in evaluating cell injury in situ.

  12. Investigation of the effects of LIFT printing with a KrF-excimer laser on thermally sensitive electrically conductive adhesives

    NARCIS (Netherlands)

    Perinchery, S.M.; Smits, E.C.P.; Sridhar, A.; Albert, P.; Brand, J. van den; Mandamparambil, R.; Yakimets, I.; Schoo, H.F.M.

    2014-01-01

    Laser induced forward transfer is an emerging material deposition technology. We investigated the feasibility of this technique for printing thermally sensitive, electrically conductive adhesives with and without using an intermediate dynamic release layer. A 248nm KrF-excimer laser was used to

  13. Excimer laser patterning of PEDOT-PSS thin-films on flexible barrier foils: a surface analysis study

    NARCIS (Netherlands)

    Naithani, S.; Schaubroeck, D.; Vercammen, Y.; Mandamparambil, R.; Yakimets, I.; Vaeck, L. van; Steenberge, G. van

    2013-01-01

    Selective laser patterning of thin organic films is an important aspect in the roll-to-roll production of organic electronic devices such as organic light emitting diodes (OLEDs). An excimer laser is well suited for the patterning and structuring of polymer thin films as their UV absorption is

  14. Coloring linens with excimer lasers to simulate the body image of the Turin Shroud

    Science.gov (United States)

    Baldacchini, Giuseppe; di Lazzaro, Paolo; Murra, Daniele; Fanti, Giulio

    2008-03-01

    The body image of the Turin Shroud has not yet been explained by traditional science; so a great interest in a possible mechanism of image formation still exists. We present preliminary results of excimer laser irradiation (wavelength of 308 nm) of a raw linen fabric and of a linen cloth. The permanent coloration of both linens is a threshold effect of the laser beam intensity, and it can be achieved only in a narrow range of irradiation parameters, which are strongly dependent on the pulse width and time sequence of laser shots. We also obtained the first direct evidence of latent images impressed on linen that appear in a relatively long period (one year) after laser irradiation that at first did not generate a clear image. The results are compared with the characteristics of the Turin Shroud, reflecting the possibility that a burst of directional ultraviolet radiation may have played a role in the formation of the Shroud image.

  15. Excimer laser micromachining of oblique microchannels on thin ...

    Indian Academy of Sciences (India)

    The edge roughness of the channels, machined with a square laser spot of side 100lm, is found to be most affected by the fluence–spot overlap interaction, and the channel width by spot-overlap and the angle of tilt of the traversed path. Polymer coated metal films underwent close to ideal machining, aided by the clamping ...

  16. Influence of microkeratome parameters on the stromal bed and flap edge quality in laser in situ keratomileusis

    Directory of Open Access Journals (Sweden)

    Heichel J

    2013-12-01

    Full Text Available Jens Heichel,1 Frank Wilhelm,2 Kathleen S Kunert,3 Rabea Schlueter,4 Ute Stuhltraeger,1 Thomas Hammer5 1Department of Ophthalmology, University Hospital of Martin Luther University Halle/Wittenberg, Halle (Saale, Germany; 2Augen im Zentrum, Greifswald, Germany; 3Department of Ophthalmology, Helios Klinikum Erfurt, Erfurt, Germany; 4Institute of Microbiology, Ernst-Moritz-Arndt-University, Greifswald, Germany; 5Augenzentrum Frohe Zukunft, Halle (Saale, Germany Purpose: Femtosecond lasers have become the standard for laser-assisted in situ keratomileusis (LASIK flap creation, but advanced mechanical microkeratomes are still an alternative, more cost-effective way to create the flap. The SCHWIND Carriazo-Pendular microkeratome is one of the most commonly used microkeratomes. The influence of different cutting parameters (head-advance speeds, cutting heads on morphology of LASIK cuts was investigated. Setting: Experimental study performed at the University Eye Hospital of the Martin Luther University Halle/Wittenberg, Halle (Saale, Germany. Methods: The Carriazo-Pendular microkeratome was used on freshly enucleated porcine eyes for lamellar keratotomy. After flap removal, the cutting edge and stromal bed were evaluated from scanning electron micrographs using an individualized scoring system. Four different settings of microkeratome parameters were compared. For each setting, eight cuts were evaluated (n=32. Results: Different oscillation frequencies and head-advance speeds did not influence the cutting qualities. A higher oscillation/feed rate ratio seemed to be advantageous for a smoother interface. Concerning different cuttings heads, a deeper keratotomy led to sharper cutting edges. The thinner the flap, the more irregularities in the stromal bed appeared. Complications did not occur. Conclusion: The Carriazo-Pendular microkeratome is a safe tool with which to create a LASIK flap and is a good alternative to a costly femtosecond laser. Deeper

  17. The Correlation Analysis between Corneal Biomechanical Properties and the Surgically Induced Corneal High-Order Aberrations after Small Incision Lenticule Extraction and Femtosecond Laser In Situ Keratomileusis

    OpenAIRE

    Wenjing Wu; Yan Wang

    2015-01-01

    Background. To investigate the correlation between corneal biomechanics and the surgically induced corneal high-order aberrations (HOAs) after small incision lenticule extraction (SMILE) and femtosecond laser in situ keratomileusis (FS-LASIK). Methods. A total of 150 right myopic eyes that underwent SMILE or FS-LASIK surgery were included in this retrospective study, 75 eyes in each group. The corneal hysteresis (CH) and the corneal resistance factor (CRF) with the corneal HOAs of the anterio...

  18. Effect of open ultraviolet germicidal irradiation lamps on functionality of excimer lasers used in cornea surgery.

    Science.gov (United States)

    Belovickis, Jaroslavas; Kurylenka, Aliaksei; Murashko, Vadim

    2017-01-01

    We report on the impact of direct ultraviolet germicidal irradiation (UVGI) on reflective optics, used in the excimer laser system Allegretto Eye-Q. The aim of our work was to confirm our hypothesis based on long-rate observations of obtained anomalies in post-operative results that are attributed to degradation of reflective optics upon ultraviolet radiation. The presence of direct UVGI coupled with humidity in the operating environment caused merging anomalies and unwanted post-operative correction values. Ultraviolet-A radiation caused a similar effect on the reflective cover of the mirrors.

  19. Preliminary results of VISX excimer laser myopic photorefractive keratectomy at Cedars-Sinai Medical Center

    Science.gov (United States)

    Maguen, Ezra I.; Berlin, Michael S.; Hofbauer, John; Macy, Jonathan I.; Nesburn, Anthony B.; Papaioannou, Thanassis; Salz, James J.

    1992-08-01

    Sixty-two eyes underwent excimer laser photorefractive keratectomy (PRK) for the correction of myopia at Cedars-Sinai-Medical-Center. The first group of 12 patients are presented with follow up data of ten months postoperatively. The second group of 50 patients are presented with follow up data of three months postoperatively. An in-depth comparison of pre and postoperative refractive data is presented. Comparisons between pre and postoperative corrected and uncorrected Snellen visual acuities are provided in order to asses the functional visual result of the procedure.

  20. Generation of large-area microscale manifolds using excimer laser ablation

    Science.gov (United States)

    Zhou, Simon; Kilgo, Marvin M., III; Williams, Charles N.

    1999-08-01

    Excimer laser ablation of polymeric materials is a widely used technology for the generation of nozzles and through- holes. Ablation is also a viable process to create more complex fluidic structures such as channels and manifolds. This paper presents recent results of experiments demonstrating the creation of manifolds in 25 micrometers polyimide films. These structures include cross-over points, and channels of various widths. The results presented include photomicrographs and SEMS, and characterization of channel wall taper and width control as well as an assessment of ablation depth uniformity over large fields. The characteristics of projection ablation systems are reviewed, and the experimental system is described in detail.

  1. Important technological problems with stable operation of electron beam pumped KrF excimer laser amplifier

    CERN Document Server

    Ma Wei Yi; Hu Feng Ming; Shan Yu Sheng; Wang Nai Yan

    2002-01-01

    Some important technological problems with stable operation of the two-side electron beam pumped main amplifier used in the 'Heaven-1' high power KrF excimer laser system are described. They are the problems of the electric breakdown of the insulator support for water dielectric transmission lines, anode foil installation of large area electron beam diode, shape of Hibachi ribs that contact the pressure foil, and formation of diode post pulses and their damage to the anode foil and cathode emitter. Emphasis is put on the effect of different main-switch breakdown times on diode post pulses and the determination of the optimal breakdown time

  2. Excimer laser reactive deposition of vanadium nitride thin films

    Science.gov (United States)

    D'Anna, E.; Di Cristoforo, A.; Fernández, M.; Leggieri, G.; Luches, A.; Majni, G.; Mengucci, P.; Nanai, L.

    2002-01-01

    We report on the deposition of thin vanadium nitride films by ablating vanadium targets in low-pressure N 2 atmosphere, and on their characterization. The targets were vanadium foils (purity 99.8%). 3 in. Si(1 1 1) wafers were used as substrates. Film characteristics (composition and crystalline structure) were studied as a function of N 2 pressure (0.5-200 Pa), KrF laser fluence (4.5-19 J/cm 2), substrate temperature (20-750 °C) and target-to-substrate distance (30-70 mm). Vanadium nitride is already formed at low N 2 ambient pressures (1 Pa) and laser fluences (6 J/cm 2) on substrates at room temperature. At the N 2 pressures of 1-10 Pa, the prevalent phase is VN. At higher pressures (100 Pa) and at relatively high laser fluences (16-19 J/cm 2), the dominant phase is V 2N. The crystallinity of the films improves by increasing the substrate temperature. Well-crystallized films are obtained on substrates heated at 500 °C.

  3. New excimer laser technique for the correction of strabismus and diplopia

    Science.gov (United States)

    Azar, Dimitri T.

    1994-06-01

    We used the ArF excimer laser to determine the feasibility of performing prismatic photoablations in model eyes (plastic spheres simulating the eye), and in rabbit corneas. This would correct diplopia and small angles of deviation, and result in minimal refractive alterations. We modified excimer laser delivery system that achieved the desired corneal contour of prismatic ablations. 193-nm argon fluoride laser was used at fluence of 160 mJ/cm2 and ablation rate 5 Hz. 5.0-mm diameter, 40 um corneal epithelial ablation were followed by 5.0- mm diameter, prismatic photokeratectomy (PPK). We were able to achieve prismatic photoablation of PMMA blocks and lenses. No other refractive changes accompanied the prismatic photoablation of PMMA blocks and lenses. No other refractive changes accompanied the prismatic effect. In rabbits re-epithelialization of the 5-mm ablations was complete by day 3, and corneal haze was not observed by gross examination. Epithelial hyperplasia and subepithelial scarring were noted at the deep edges. PPK holds important therapeutic potential for fine-tuning results of conventional strabismus surgery, and for patients with stable diplopia following nerve palsy and ocular surgery.

  4. Photo-triggering and secondary electron produced ionization in electric discharge ArF* excimer lasers

    Science.gov (United States)

    Xiong, Zhongmin; Kushner, Mark J.

    2011-10-01

    Electric discharge excimer lasers are sustained in multi-atmosphere attaching gas mixtures that are typically preionized to enable a reproducible, uniform glow, which maximizes optical quality and gain. This preionization is often accomplished using UV light produced by a corona discharge within the plasma cavity. To quantify the relationship between corona discharge properties and those of the laser discharge, the triggering of electron avalanche by preionizing UV light in an electric discharge-pumped ArF* excimer laser was numerically investigated using a two-dimensional model. The preionizing UV fluxes were generated by a corona-bar discharge driven by the same voltage pulse as the main discharge sustained in a multi-atmospheric Ne/Ar/Xe/F2 gas mixture. The resulting peak photo-electron density in the inter-electrode spacing is around 108 cm-3, and its distribution is biased toward the UV source. The preionization density increases with increasing dielectric constant and capacitance of the corona bar. The symmetry and uniformity of the discharge are, however, improved significantly once the main avalanche develops. In addition to bulk electron impact ionization, the ionization generated by sheath accelerated secondary electrons was found to be important in sustaining the discharge current at experimentally observed values. At peak current, the magnitude of the ionization by sheath accelerated electrons is comparable to that from bulk electron impact in the vicinity of the cathode.

  5. Colouring fabrics with excimer lasers to simulate encoded images: the case of the Shroud of Turin

    Science.gov (United States)

    Di Lazzaro, P.; Baldacchini, G.; Fanti, G.; Murra, D.; Santoni, A.

    2008-10-01

    The faint body image embedded into the Turin Shroud has not yet explained by traditional science. We present experimental results of excimer laser irradiation (wavelengths 308 nm and 193 nm) of a raw linen fabric and of a linen cloth, seeking for a possible mechanism of image formation. The permanent coloration of both linens is a threshold effect on the laser beam intensity and it can be achieved only in a surprisingly narrow range of irradiation parameters: the shorter the wavelength, the narrower the range. We also obtained the first direct evidence of latent images impressed on linen that appear in a relatively long period (one year) after a laser irradiation that at first did not generate a clear image. The results are compared to the characteristics of the Turin Shroud, commenting the possibility that a burst of directional ultraviolet radiation may have played a role in the formation of the Shroud image.

  6. Applicability of KrF excimer laser induced fluorescence in sooting high-pressure flames

    Energy Technology Data Exchange (ETDEWEB)

    Hildenbrandt, F.; Schulz, C.; Sick, V.; Jander, H.; Wagner, H.G.

    1999-07-01

    Laser-induced emissions obtained after excitation with a tunable KrF excimer laser at 248 nm were measured in well-defined sooting laminar high-pressure flames fueled with methane/air and ethylene/air up to 15 bar. A spectral analysis shows that Mie scattering, Raman scattering and laser-induced fluorescence (LIF) signals can be used for detailed flame studies under sooting high-pressure conditions. Mie scattering is correlated with soot, Raman signals can be used to measure spatially-resolved major species concentrations as well as temperatures. A LIF-scheme to measure NO was found to be applicable even under these conditions. The broadband fluorescence in the range from 270 to 290 nm, usually discarded as background, correlates well with the total concentration of polycyclic aromatic hydrocarbons (PAH) as measured via GC-MS methods. (orig.)

  7. Processing of bioglass coatings by excimer laser ablation

    Energy Technology Data Exchange (ETDEWEB)

    Serra, J.; Gonzalez, P.; Chiussi, S.; Leon, B.; Perez-Amor, M. [Vigo Univ. (Spain). Dept. de Fisica Aplicada

    2001-07-01

    Bioglass (BG) coatings have been prepared in different N{sub 2}O atmospheres by pulsed laser deposition (PLD) using a BG target and an ArF laser. Changes in composition and refractive index were observed by Fourier transform infrared spectroscopy (FTIR), energy dispersive spectroscopy (EDS) and single-wavelength ellipsometry. Film thicknesses were measured by profilometry and surface morphology was observed by scanning electron microscopy (SEM). It has been shown that target composition is transferred to the substrate and that films properties can be modified using different N{sub 2}O atmospheres during the growth process. We observed also a gradual variation of the film refractive index with increasing N{sub 2}O pressures and FTIR spectra reveal that the formation of non-bridging oxygen bonds in the coatings can be controlled. It is well-known, that these bond units determine the formation of apatite on the surfaces of bioactive glass coatings (BGCs) after being soaked in simulated body fluid (SBF), which is an essential characteristic of biocompatibility. (orig.)

  8. Regression and wound healing after excimer laser PRK: a histopathological study on human corneas.

    Science.gov (United States)

    Lohmann, C P; Patmore, A; O'Brart, D; Reischl, U; Winkler Mohrenfels, C; Marshall, J

    1997-01-01

    The results of excimer laser PRK are promising as more than 80% of eyes with up to -6.0 diopters of attempted correction have refractive results within 1.0 diopter of emmetropia. However, throughout the dioptric range some unexpected results have been observed with individual patients showing an aggressive wound healing response with excessive myopic regression and severe corneal haze. Unfortunately, only limited data are available about the cellular and extracellular responses in human corneas after PRK and this information is important to establish adequate postoperative pharmaceutical treatment. We made a histopathological and immunohistochemical study on 20 human corneal samples from patients with severe corneal haze and myopic regression. The indirect immunofluorescence method was used for demonstration of collagen types I, III, IV laminin, chondroitin sulphate, dermatan sulphate, and keratin. All corneal specimens showed a hyperplastic epithelium. Histologically, most samples (16/20) showed mainly a loose lamination of extracellular material which could be identified as collagen type IV. The remaining four samples had newly synthesised collagen type III. Our histopathological results indicate that corneal wound healing after excimer laser PRK varies among individuals. In some people epithelial basement proteins, such as collagen type IV, are the main wound healing products, whereas in others mainly collagen type III is found postoperatively, which does not effect the synthesis of collagen type IV. This suggests the need for individually-tailored postoperative pharmaceutical treatment regimens.

  9. Immunofluorescence study of corneal wound healing after excimer laser anterior keratectomy in the monkey eye.

    Science.gov (United States)

    Malley, D S; Steinert, R F; Puliafito, C A; Dobi, E T

    1990-09-01

    We performed anterior keratectomies on six monkey eyes, four by excimer laser large-area ablation at 193 nm and two by mechanical keratectomy. Immunofluorescence was used to study the wound healing response histopathologically. The distribution of fibrinogen, fibronectin, laminin, collagen types III, IV, and VI, and keratan sulfate was determined at postoperative intervals of 24 hours, 6 days, and 1 month. At 24 hours, fibrinogen and fibronectin coated the ablated surface, but corneal epithelial cells had not yet migrated over the wound. By 6 days and persisting at 1 month, an epithelial ingrowth of seven to 10 layers, mild stromal hypercellularity, and new collagen formation were present in the repair region. At 1 month, fibrinogen, fibronectin, laminin, and type III collagen were strongly detected in the repair region. Type VI collagen was present in both normal and healed corneal stroma at all intervals, and type IV collagen was present in Descemet's membrane only. Sulfated keratan sulfate was absent from the newly synthesized collagen stroma at all intervals. Slit-lamp photographs demonstrated corneal haze in the ablation zone in all cases at 24 hours, persisting for 1 month. The fluorescence patterns produced by excimer laser ablation and mechanical keratectomy were qualitatively identical.

  10. A new transepithelial phototherapeutic keratectomy mode using the NIDEK CXIII excimer laser.

    Science.gov (United States)

    Buzzonetti, Luca; Petrocelli, Gianni; Laborante, Antonio; Mazzilli, Emilio; Gaspari, Mario; Valente, Paola; Francia, Elisa

    2009-01-01

    To evaluate epithelial healing, postoperative pain, and best spectacle-corrected visual acuity (BSCVA) after transepithelial photorefractive keratectomy (PRK) performed with a new phototherapeutic keratectomy (PTK) mode using the NIDEK CXIII excimer laser. Fifteen eyes from 10 patients with myopia underwent transepithelial PRK using a multistage program to perform PTK followed by PRK. The PTK incorporated Flex Scan, which accounts for the loss of radial ablation efficiency on the peripheral cornea. The epithelium was removed with the excimer laser by monitoring the disappearance of blue fluorescence during the ablation. Epithelial healing was evaluated by taking slit-lamp photographs every 24 hours until complete reepithelialization. Postoperative pain was measured according to the Faces Pain Rating Scale. All outcomes are reported for 3 months postoperatively. Haze was graded by two ophthalmologists, each masked to the other's result. Mean reepithelialization took 3.50+/-0.85 days, mean pain score was 3.00+/-1.20, and BSCVA was 20/20 for 9 eyes, 20/30 for 3 eyes, and 20/40 for 3 eyes. All patients had haze below grade 2. The outcomes of the preliminary study show that the incorporation of the Flex Scan algorithm in the PTK mode is as safe and effective as conventional PTK algorithms. The primary advantage of this new PTK mode may be more consistent epithelial removal. Additional studies are needed to determine long-term outcomes.

  11. Pain after epithelial removal by ethanol-assisted mechanical versus transepithelial excimer laser debridement.

    Science.gov (United States)

    Kanitkar, K D; Camp, J; Humble, H; Shen, D J; Wang, M X

    2000-01-01

    To compare subjective pain responses between two techniques of epithelial removal prior to photorefractive keratectomy (PRK) treatment: ethanol-soaked pledget with mechanical debridement of the epithelium versus excimer laser transepithelial ablation. Nine patients underwent bilateral PRK. Each had the epithelium in one eye debrided by placing a pledget soaked in 20% ethanol on the cornea for 2 minutes followed by gentle scraping with a blade. The epithelium in the other eye was removed by transepithelial phototherapeutic keratectomy (PTK) treatment. For each eye, PRK was initiated immediately after removal of the epithelium. On postoperative day one, each patient was asked to rate the level of pain suffered over the last 24 hours on a scale of 0 (minimal) to 10 (maximal). Data were analyzed in a masked fashion. Postoperative day one average pain level in the ethanol-assisted mechanically debrided eyes was 3.0 +/- 2.5 and in the transepithelial PTK eyes was 6.8 +/- 1.8. The difference was statistically significant by Student's t-test (P < .01). All epithelial defects healed within 3 days with no clinically significant difference in healing time between the two techniques. In preparation for PRK, ethanol-assisted mechanical debridement of the epithelium caused significantly less postoperative pain than epithelial removal using the excimer laser.

  12. Femtosecond (FS) laser vision correction procedure for moderate to high myopia: a prospective study of ReLEx(®) flex and comparison with a retrospective study of FS-laser in situ keratomileusis

    DEFF Research Database (Denmark)

    Vestergaard, Anders; Ivarsen, Anders; Asp, Sven

    2013-01-01

    Purpose:  To present our initial clinical experience with ReLEx(®) flex (ReLEx) for moderate to high myopia. We compare efficacy, safety and corneal higher-order aberrations after ReLEx with femtosecond laser in situ keratomileusis (FS-LASIK). Methods:  Prospective study of ReLEx compared...

  13. Validade da topografia de córnea na cirurgia refrativa com excimer laser Validity of corneal topography in refractive surgery with excimer laser

    Directory of Open Access Journals (Sweden)

    Orlando da Silva Filho

    2003-12-01

    Full Text Available OBJETIVO: Avaliar os resultados refracionais e a segurança do procedimento cirúrgico PRK (ceratectomia fotorrefrativa com base na topografia de córnea no pré-operatório. MÉTODOS: Participantes - 44 sujeitos que tinham realizado cirurgia refrativa, com o procedimento ceratectomia fotorrefrativa, os quais apresentaram topografias irregulares pré-operatórias. O grupo controle consistiu de 44 sujeitos com topografia regular pré-operatória. Os 88 olhos foram submetidos a ceratectomia fotorrefrativa utilizando-se o "Summit Apex plus Excimer Laser". As topografias irregulares e regulares foram obtidas pelo "Corneal Analysis System"(EyeSys, sendo consideradas como topografias irregulares os seguintes achados: ápice deslocado acima de 1,5 D (AD, asfericidade maior que 0,25 D/mm (AS, obliquidade maior que 15 graus (OB, assimetria inferior-superior igual ou maior que 1,5 D (IS, curvatura maior que 47 D (CU e combinação de 2 critérios (CB. Principal efeito medido: perda de uma ou mais linhas que foram definidas com segurança para o prognóstico. RESULTADOS: Todos os pacientes foram acompanhados por 6 meses. Verificou-se perda significativa de acuidade visual corrigida em pacientes submetidos ao procedimento PRK-AD (pPURPOSE: To evaluate the refractive results and safety of PRK (photorefractive keratectomy based on the preoperative corneal topography. METHODS: 44 operated eyes, using the photorefractive keratectomy process, and which presented preoperative topographical abnormalities. The control group consisted of 44 eyes with preoperative normal corneal topography. Eighty-eight eyes were submitted to the photorefractive keratectomy process using the Summit Apex plus Excimer Laser. Corneal topographies were accessed by the EyeSys Analysis system; the topographic abnormalities which were considered are the following: apex displacement above 1.5D (AD, asphericity above 0.25D/mm (AS, obliquity above 15 degrees (OB, inferior-superior asymmetry

  14. Excimer laser texturing of natural composite polymer surfaces for studying cell-to-substrate specific response

    Science.gov (United States)

    Dinca, V.; Alloncle, P.; Delaporte, P.; Ion, V.; Rusen, L.; Filipescu, M.; Mustaciosu, C.; Luculescu, C.; Dinescu, M.

    2015-10-01

    Surface modifications of biocompatible materials are among the main factors used for enhancing and promoting specific cellular activities (e.g. spreading, adhesion, migration, and differentiation) for various types of medical applications such as implants, microfluidic devices, or tissue engineering scaffolds. In this work an excimer laser at 193 nm was used to fabricate chitosan-collagen roughness gradients. The roughness gradients were obtained in one step by applying single laser pulses and sample tilting. Fourier transform infrared spectroscopy measurements, atomic force microscopy (AFM), scanning electron microscopy (SEM), and spectro-ellipsometry (SE) were used for sample characterization. The goal is to determine the optimal morpho-chemical characteristics of these structures for in vitro tailoring of protein adsorption and cell behavior. The response induced by the roughness gradient onto various cell lines (i.e. L 929 fibroblasts, HEP G2 hepatocytes, OLN 93 oligodendrocytes, M63 osteoblasts) and bovine serum albumin (BSA) protein absorption was investigated.

  15. Time-resolved spectroscopy and fluorescence resonance energy transfer in the study of excimer laser damage of chromatin

    Energy Technology Data Exchange (ETDEWEB)

    Radu, L. [Department of Molecular Genetics and Radiobiology, Babes National Institute, Bucharest (Romania)], E-mail: lilianajradu@yahoo.fr; Mihailescu, I. [Department of Lasers, Laser, Plasma and Radiation Physics Institute, Bucharest (Romania); Radu, S. [Department of Computer Science, Polytechnics University, Bucharest (Romania); Gazdaru, D. [Department of Biophysics, Bucharest University (Romania)

    2007-09-21

    The analysis of chromatin damage produced by a 248 nm excimer laser radiation, for doses of 0.3-3 MJ/m{sup 2} was carried out by time-resolved spectroscopy and fluorescence resonance energy transfer (FRET). The chromatin was extracted from a normal and a tumoral tissue of Wistar rats. The decrease with laser dose of the relative contribution of the excited state lifetimes of ethidium bromide (EtBr) bounded to chromatin constitutes an evidence of the reduction of chromatin deoxyribonucleic acid (DNA) double-strand structure. FRET was performed from dansyl chloride to acridine orange, both coupled to chromatin. The increase of the average distance between these ligands, under the action of laser radiation, reflects a loosening of the chromatin structure. The radiosensitivity of tumor tissue chromatin is higher than that of a normal tissue. The determination of the chromatin structure modification in an excimer laser field can be of interest in laser therapy.

  16. Evaluation of the efficacy of excimer laser ablation of cross-linked porcine cornea.

    Directory of Open Access Journals (Sweden)

    Shihao Chen

    Full Text Available BACKGROUND: Combination of riboflavin/UVA cross-linking (CXL and excimer laser ablation is a promising therapy for treating corneal ectasia. The cornea is strengthened by cross-linking, while the irregular astigmatism is reduced by laser ablation. This study aims to compare the efficacy of excimer laser ablation on porcine corneas with and without cross-linking. METHODS AND FINDINGS: The porcine cornea was de-epithelialized and treated with 0.1% riboflavin solution for 30 minutes. A half of the cornea was exposed to UVA-radiation for another 30 minutes while the controlled half of the cornea was protected from the UVA using a metal shield. Photo therapeutic keratectomy (PTK was then performed on the central cornea. Corneal thickness of 5 paired locations on the horizontal line, ± 0.5, ± 1.0, ± 1.5, ± 2.0, and ± 2.5 mm from the central spot, were measured using optical coherence tomography prior to and after PTK. The ablation depth was then determined by the corneal thickness. There was a 9% difference (P<0.001 in the overall ablation depth between the CXL-half corneas (158 ± 22 µm and the control-half corneas (174 ± 26 µm. The ablation depths of all 5 correspondent locations on the CXL-half were significantly smaller (P<0.001. CONCLUSION: The efficacy of the laser ablation seems to be lower in cross-linked cornea. Current ablation algorithms may need to be modified for cross-linked corneas.

  17. Eye-Tracker-Guided Non-Mechanical Excimer Laser Assisted Penetrating Keratoplasty

    Directory of Open Access Journals (Sweden)

    Achim Langenbucher

    2013-03-01

    Full Text Available Purpose: The purpose of the study was to implement a new eye tracking mask which could be used to guide the laser beam in automated non-mechanical excimer laser assisted penetrating keratoplasty. Materials and methods: A new trephination mask design with an elevated surface geometry has been proposed with a step formation between conical and flat interfaces. Two recipient masks of 7.5/8.0 mm have been manufactured and tested. The masks have outer diameter of 12.5 mm, step formation at 10.5 mm, and slope of conical surfaces 15°. Its functionality has been tested in different lateral positions and tilts on a planar surface, and pig eye experiments. After successful validation on porcine eyes, new masks have been produced and tested on two patients. Results: The build-in eye tracking software of the MEL 70 was always able to capture the masks. It has been shown that the unwanted pigmentation/pattern induced by the laser pulses on the mask surface does not influence the eye-tracking efficiency. The masks could be tracked within the 18 × 14 mm lateral displacement and up to 12° tilt. Two patient cases are demonstrated. No complications were observed during the surgery, although it needs some attention for aligning the mask horizontally before trephination. Stability of eye tracking masks is emphasized by inducing on purpose movements of the patient head. Conclusion: Eye-tracking-guided penetrating keratoplasty was successfully applied in clinical practice, which enables robust tracking criteria within an extended range. It facilitates the automated trephination procedure of excimer laser-assisted penetrating keratoplasty.

  18. Effect of preionization, fluorine concentration, and current density on the discharge uniformity in F2 excimer laser gas mixtures

    NARCIS (Netherlands)

    Mathew, D.; Bastiaens, Hubertus M.J.; Boller, Klaus J.; Peters, P.J.M.

    2007-01-01

    The discharge homogeneity in F2-based excimer laser gas mixtures and its dependence on various key parameters, such as the degree of preionization, preionization delay time, F2 concentration and current density, is investigated in a small x-ray preionized discharge chamber. The spatial and temporal

  19. Evaluation and diffusion of excimer laser treatment of myopia in the United States and in the Netherlands

    NARCIS (Netherlands)

    Vondeling, H.; Rosendal, H.; Banta, D.

    1995-01-01

    Excimer laser photorefractive keratectomy (PRK) is an experimental treatment to correct myopia (short-sightedness) that is diffusing into use without convincing evidence of safety and efficacy. It has been claimed that PRK may render conventional methods of correcting myopia, such as wearing glasses

  20. Efficacy of brimonidine tartrate 0.2% ophthalmic solution in reducing halos after laser in situ keratomileusis.

    Science.gov (United States)

    Lee, Ji Hoon; You, Yong Sung; Choe, Chul Myong; Lee, Eun Suk

    2008-06-01

    To quantitatively evaluate the effect of brimonidine tartrate 0.2% (Alphagan) on halo and pupil size in patients who had symptomatic night-vision difficulties after laser in situ keratomileusis (LASIK). Nune Eye Hospital, Seoul, Korea. This study comprised 28 eyes of 14 patients with symptomatic night-vision difficulties after LASIK. Pupil diameter was measured with a Colvard pupillometer (Oasis Medical, Inc.). Quantitative analysis of halos was performed by measuring the area using a new computerized method. Pupil size and halo size were evaluated under scotopic and normal room light conditions. Alphagan was administered, and the effect was measured after 30 minutes and 1, 6, 12, and 24 hours. There was a statistically significant correlation between pupil size and halo size (r = 0.527; P<.0001; slope = 691.6 pixel/mm). Pupil size and halo size decreased significantly 30 minutes after Alphagan instillation under both luminance conditions (all P< .0001). Under normal room light, the pupil and halo remained decreased until the last measurement at 24 hours. Under scotopic conditions, the pupil returned to its preinstillation size at 24 hours while the halo remained decreased. The maximum effect on halos was observed after 6 hours, when the mean reduction over preinstillation size was 28.2% and 29.1% under normal room light conditions and scotopic conditions, respectively. Alphagan effectively reduced halo size and pupil size in postoperative LASIK patients with night-vision symptoms.

  1. Effects of ablation depth and repair time on the corneal elastic modulus after laser in situ keratomileusis.

    Science.gov (United States)

    Wang, Xiaojun; Li, Xiaona; Chen, Weiyi; He, Rui; Gao, Zhipeng; Feng, Pengfei

    2017-01-17

    The biomechanical properties of the cornea should be taken into account in the refractive procedure in order to perform refractive surgery more accurately. The effects of the ablation depth and repair time on the elastic modulus of the rabbit cornea after laser in situ keratomileusis (LASIK) are still unclear. In this study, LASIK was performed on New Zealand rabbits with different ablation depth (only typical LASIK flaps were created; residual stroma bed was 50 or 30% of the whole cornea thickness respectively). The animals without any treatment were served as normal controls. The corneal thickness was measured by ultrasonic pachymetry before animals were humanly killed after 7 or 28 days post-operatively. The corneal elastic modulus was measured by uniaxial tensile testing. A mathematical procedure considering the actual geometrics of the cornea was created to analyze the corneal elastic modulus. There were no obvious differences among all groups in the elastic modulus on after 7 days post-operatively. However, after 28th days post-operatively, there was a significant increase in the elastic modulus with 50 and 30% residual stroma bed; only the elastic modulus of the cornea with 30% residual stroma bed was significantly higher than that of 7 days. Changes in elastic modulus after LASIK suggest that this biomechanical effect may correlate with the ablation depth and repair time.

  2. Influence of flap thickness on visual and refractive outcomes after laser in situ keratomileusis performed with a mechanical keratome.

    Science.gov (United States)

    Bansal, Alok S; Doherty, Terrence; Randleman, J Bradley; Stulting, R Doyle

    2010-05-01

    To study the effect of flap thickness on visual acuity and refractive outcomes after laser in situ keratomileusis (LASIK) using 2 blade types with a mechanical microkeratome. Emory Vision, Atlanta, Georgia, USA. This retrospective analysis was of LASIK cases performed between January 2005 and June 2006 using an Amadeus I microkeratome and an ML7090 CLB blade (blade A) or a Surepass blade (blade B). Outcomes analyzed included flap thickness, uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest refraction spherical equivalent (MRSE), the enhancement rate, and surgical complications 3 months postoperatively. Two hundred sixty-three eyes of 153 patients were analyzed; blade A was used in 158 eyes and blade B, in 105 eyes. The mean flap thickness was significantly thinner with blade A than with blade B (107 microm +/- 12 [SD] versus 130 +/- 20 microm) (P .10), and there was no difference in the complication rates. Flap thickness did not affect visual or refractive outcomes with a mechanical microkeratome with either blade type. (c) 2010 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  3. Risk for microbial keratitis: Comparative metaanalysis of contact lens wearers and post-laser in situ keratomileusis patients.

    Science.gov (United States)

    Masters, Jordan; Kocak, Mehmet; Waite, Aaron

    2017-01-01

    To compare the risk for microbial keratitis in contact lens wearers stratified by wear schedule with the risk after laser in situ keratomileusis (LASIK). Hamilton Eye Institute and Department of Ophthalmology, University of Tennessee Health Science Center, Memphis, Tennessee, USA. Comparative metaanalysis and literature review. An extensive literature search was performed in the PubMed database between December 2014 and July 2015. This was followed by a metaanalysis using a mixed-effects modeling approach. After 1 year of daily soft contact lens wear, there were fewer microbial keratitis cases than after LASIK, or approximately 2 cases fewer cases per 10 000 (P = .0609). If LASIK were assumed to have essentially a 1-time risk for microbial keratitis, 5 years of extrapolation would yield 11 more cases per 10 000 with daily soft contact lens wear than with LASIK, or approximately 3 times as many cases (P contact lenses led to 12 more cases at 1 year than LASIK, or approximately 3 times as many cases (P contact lens use and LASIK postoperatively. The risk for microbial keratitis was similar between patients using contact lenses for 1 year compared with LASIK. Over time, the risk for microbial keratitis was higher for contact lens use than for LASIK, specifically with extended-wear lenses. Copyright © 2016 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  4. Comparison of biomechanical effects of small-incision lenticule extraction and laser in situ keratomileusis: finite-element analysis.

    Science.gov (United States)

    Sinha Roy, Abhijit; Dupps, William J; Roberts, Cynthia J

    2014-06-01

    To theoretically compare the corneal stress distribution of laser in situ keratomileusis (LASIK) with the stress distribution of small-incision lenticule extraction. Cleveland Clinic Cole Institute, Cleveland, and The Ohio State University, Columbus, Ohio, USA. Computational modeling study. A finite-element anisotropic collagen fiber-dependent model of myopic surgery using patient-specific corneal geometry was constructed for LASIK, small-incision lenticule extraction, and a geometry analog model with unaltered material properties from preoperative but with postoperative geometry including thickness. Surgical parameters, magnitude of myopic correction, LASIK flap thickness, and lenticule depth in small-incision lenticule extraction were varied. Two sets of models, 1 with uniform and 1 with depth-dependent material properties, were constructed. Stress distribution between small-incision lenticule extraction simulations and the geometry analog model were similar. In contrast, LASIK consistently reduced stress in the flap and increased stress in the residual stromal bed (RSB) compared with the geometry analog model. An increase in flap thickness or lenticule depth resulted in a greater increase in RSB stress in the LASIK model than in the small-incision lenticule extraction model. Small-incision lenticule extraction may present less biomechanical risk to the residual bed of susceptible corneas than comparable corrections involving LASIK flaps. Deeper corrections in the stroma may be possible in small-incision lenticule extraction without added risk for ectasia. Proprietary or commercial disclosures are listed after the references. Copyright © 2014 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  5. Laser-assisted in situ keratomileusis for correction of astigmatism and increasing contact lens tolerance after penetrating keratoplasty.

    Science.gov (United States)

    Park, Chang-Hyun; Kim, Su-Young; Kim, Man-Soo

    2014-10-01

    To determine effectiveness of laser-assisted in situ keratomileusis (LASIK) in the treatment of astigmatism following penetrating keratoplasty (PK). We performed a retrospective review of medical records of patients who underwent LASIK following PK and had over 1 year of follow-up data. Twenty-six patients (26 pairs of eyes) underwent LASIK following PK. Mean age of the patients at the time of LASIK was 40.7 years (range, 26 to 72 years). Following LASIK, the mean cylinder was reduced by 2.4 diopters and mean reduction of cylinder after LASIK was 65.4% from the preoperative values at the last follow-up visit. Uncorrected visual acuity became 20 / 50 or better in 69.2% of the eyes after LASIK. Best-corrected visual acuity became 20 / 50 or better in 73.1% of the eyes after LASIK. All of them were intolerable to contact lenses before LASIK. After LASIK, 6 pairs (23.1%) did not need to use contact lenses and 18 pairs (69.2%) were tolerable to using contact lenses or spectacles. There were no significant endothelial cell density changes 12 months after LASIK (p = 0.239). LASIK is effective in the treatment of astigmatism following PK and increases contact lens and spectacle tolerance.

  6. Combination therapy with diquafosol tetrasodium and sodium hyaluronate in patients with dry eye after laser in situ keratomileusis.

    Science.gov (United States)

    Toda, Ikuko; Ide, Takeshi; Fukumoto, Teruki; Ichihashi, Yoshiyuki; Tsubota, Kazuo

    2014-03-01

    To evaluate the possible advantages of combination therapy with diquafosol tetrasodium and sodium hyaluronate for dry eye after laser in situ keratomileusis (LASIK). Prospective randomized comparative trial. A total of 206 eyes of 105 patients who underwent LASIK were enrolled in this study. Patients were randomly assigned to 1 of 4 treatment groups according to the postoperative treatment: artificial tears, sodium hyaluronate, diquafosol tetrasodium, and a combination of hyaluronate and diquafosol. Questionnaire responses reflecting subjective dry eye symptoms, uncorrected and corrected visual acuity, functional visual acuity, manifest refraction, tear break-up time, fluorescein corneal staining, Schirmer test, and corneal sensitivity were examined before and 1 week and 1 month after LASIK. Distance uncorrected visual acuity was significantly better in the combination group than in the hyaluronate group 1 week and 1 month after LASIK. Near uncorrected visual acuity was significantly better in the combination group than in the artificial tear and diquafosol groups 1 week and 1 month after LASIK. Distance functional visual acuity improved significantly only in the combination group 1 month after LASIK. The Schirmer value in the combination group was significantly higher than that in the hyaluronate group at 1 month after LASIK. Subjective dry eye symptoms in the combination group improved significantly compared with those in the other groups 1 week after surgery. Our results suggest that hyaluronate and diquafosol combination therapy is beneficial for early stabilization of visual performance and improvement of subjective dry eye symptoms in patients after LASIK. Copyright © 2014 Elsevier Inc. All rights reserved.

  7. Fabrication of the Long Bragg Grating by Excimer Laser Micro Machining with High-Precision Positioning XXY Platform

    Directory of Open Access Journals (Sweden)

    Jian-Zhong Wu

    2014-03-01

    Full Text Available With the advancement of technology, the application of fiber Bragg grating is widely used as a Bragg grating sensor. Fiber Bragg grating is fabrication using excimer laser machining with the phase masker. The grating length is decided by the width of laser beam. In this paper, we proposed fabrication of the long Bragg grating by excimer Laser micro machining with a high-precision positioning XXY platform. The high-precision positioning XXY platform plays an important role for long FBG. It needs seriously to combine three short FBGs. Therefore, we can obtain a long FBG with 15mm length. This method can provide a solution to fabricate long FBG by using cheap laser with high-precision positioning XXY platform.

  8. Laser-assisted subepithelial keratectomy (LASEK) versus laser-assisted in-situ keratomileusis (LASIK) for correcting myopia.

    Science.gov (United States)

    Kuryan, Jocelyn; Cheema, Anjum; Chuck, Roy S

    2017-02-15

    Near-sightedness, or myopia, is a condition in which light rays entering the eye along the visual axis focus in front of the retina, resulting in blurred vision. Myopia can be treated with spectacles, contact lenses, or refractive surgery. Options for refractive surgery include laser-assisted subepithelial keratectomy (LASEK) and laser-assisted in-situ keratomileusis (LASIK). Both procedures utilize a laser to shape the corneal tissue (front of the eye) to correct refractive error, and both create flaps before laser treatment of corneal stromal tissue. Whereas the flap in LASEK is more superficial and epithelial, in LASIK it is thicker and also includes some anterior stromal tissue. LASEK is considered a surface ablation procedure, much like its predecessor, photorefractive keratectomy (PRK). LASEK was developed as an alternative to PRK to address the issue of pain associated with epithelial debridement used for PRK. Assessing the relative benefits and risks/side effects of LASEK and LASIK warrants a systematic review. To assess the effects of LASEK versus LASIK for correcting myopia. We searched the Cochrane Central Register of Controlled Trials (CENTRAL), which contains the Cochrane Eyes and Vision Trials Register (2016, Issue 10); MEDLINE Ovid (1946 to 24 October 2016); Embase.com (1947 to 24 October 2016); PubMed (1948 to 24 October 2016); LILACS (Latin American and Caribbean Health Sciences Literature Database; 1982 to 24 October 2016); the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), last searched 20 June 2014; ClinicalTrials.gov (www.clinicaltrials.gov); searched 24 October 2016; and the WHO International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en); searched 24 October 2016. We did not use any date or language restrictions in the electronic searches for trials. We considered only randomized controlled trials (RCTs) for the purposes of this review. Eligible RCTs were those in which myopic participants were

  9. Excimer laser cleaning of encrustation on Pentelic marble: procedure and evaluation of the effects

    Science.gov (United States)

    Maravelaki-Kalaitzaki, P.; Zafiropulos, V.; Fotakis, C.

    1999-06-01

    This work focuses on the use and control of excimer lasers (KrF, λ=248 nm and XeCl, λ=308 nm) for the removal of encrustation (black crusts, soil-dust and biological deposits) from Pentelic marble. A number of surface analytical techniques, such as Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) interfaced with microprobe analysis (energy dispersive X-ray analysis: EDX), X-ray diffraction (XRD), laser-induced breakdown spectroscopy (LIBS) and optical microscopy (OM) were used to detect chemical composition and crust morphology, as well as to monitor the effects induced by the laser treatment. SEM and OM providing structural information about the layers of encrustation, LIBS and SEM-EDX providing information on the elemental composition of the ablated material, XRD and FTIR detecting the changes of minerals appear to be particularly effective in assessing the quality of cleaning process. FTIR and XRD showed removal of pollutants from encrustation and partial transformation of calcium sulfate dihydrate (gypsum) to hemihydrate and anhydrite, which have lower specific surface than gypsum. Irradiation conditions creating minimal damaging effects were defined before treatment through surface analysis, ablation rate studies and optimization of laser parameters. On the basis of structural and analytical examinations, both lasers are shown to be appropriate for achieving sufficient removal of unwanted selected layers without modifying the surface morphology and surpassing by far the effectiveness afforded by traditional cleaning techniques.

  10. Fluorescence imaging inside an internal combustion engine using tunable excimer lasers.

    Science.gov (United States)

    Andresen, P; Meijer, G; Schlüter, H; Voges, H; Koch, A; Hentschel, W; Oppermann, W; Rothe, E

    1990-06-01

    Tunable excimer lasers are used to obtain 2-D images of molecular (and some state-specific) density distributions inside a cylinder of a modified four-cylinder in-line engine that has optical access. Natural fluorescence (i.e., without a laser) is used for some OH pictures, normal laser-induced fluorescence (LIF) for those of NO and of the isooctane fuel, and laser-induced predissociative fluorescence (LIPF) for other OH pictures and for those of O(2). Relevant spectroscopy is done to find the laser and fluorescence frequencies needed to measure isolated species. LIPF works well at high pressures, is state specific, and is ideally suited to follow turbulent processes. No similar measurements in engines have been previously reported. Pictures are taken in succeeding engine cycles. Their sequence is either at a particular point of the engine's cycle to show cyclic fluctuations, or at succeeding portions of the cycle to illustrate the progress of the gasdynamics or of the combustion.

  11. Alternatives to excimer laser refractive surgery: UV and mid-infrared laser ablation of intraocular lenses and porcine cornea

    Science.gov (United States)

    Serafetinides, A. A.; Makropoulou, M.; Spyratou, E.; Bacharis, C.

    2007-03-01

    Despite the fact that the laser applications in human ophthalmology are well established, further research is still required, for better and predictable ablation dosimetry on both cornea tissue and intraocular lenses. Further studies for alternative laser sources to the well established excimer lasers, such as UV or mid-infrared solid state lasers, have been proposed for refractive surgery. The precise lens ablation requires the use of laser wavelengths possessing a small optical penetration depth in the cornea and in the synthetic lenses, in order to confine the laser energy deposition to a small volume. In order to eliminate some very well known problems concerning the reshaping of cornea and the modification of the optical properties of the intraocular lenses, ablation experiments of ex vivo porcine cornea, acrylic PMMA and hydrophilic lenses were conducted with an Er:YAG laser (2.94 μm) and the fifth harmonic of a Nd:YAG laser (213 nm). The morphology of cornea was recorded using a cornea topography system before and immediately after the ablation. Histology analysis of the specimens was obtained, in order to examine the microscopic appearance of the ablated craters and the existence of any thermal damage caused by the mid-infrared and UV laser irradiation. The macroscopic morphology of the intraocular lens craters was inspected with an optical transmission microscope. Measurements of the ablation rates of the lenses were performed and simulated by a mathematical model.

  12. Excimer-laser-based multifunctional patterning systems for optoelectronics, MEMS, materials processing, and biotechnology

    Science.gov (United States)

    Jain, Kanti

    2003-07-01

    Over the past few years, there has been an increasing impact of microelectronics fabrication technologies on the realization of structures and spatial patterns necessary for advances in optoelectronics, MEMS, materials processing, and biotechnology. These fabrication technologies accelerate the pace of research by enabling the micro-manipulation and patterning of a variety of organic, inorganic, and biological materials (including new polymers, compound semiconductors, DNA, proteins, and others), developing new synthesis techniques, and producing structures and devices previously not deemed possible. In order to facilitate the exploration of these fields, it is desirable to develop processing techniques and cost-effective, multifunctional systems that can handle a wide variety of substrate materials and geometries, including non-planar surfaces. This paper describes recent advances made in excimer-laser-based patterning, photoablation, and photo-crystallization technologies, focusing on how these technologies address the unique requirements of applications for scientific research and for technology development.

  13. Interaction of 308-nm excimer laser light with temporomandibular joint related structures

    Science.gov (United States)

    Liesenhoff, Tim; Funk, Armin

    1994-02-01

    Arthroscopy of TMJ has become a clinically important and more and more accepted method for diagnosis and treatment of TMJ alteration. This minimal invasive method is clearly limited by the anatomical dimensions of the TMJ. A 308 nm excimer laserlight has already found clinical applications in angioplasty, ophthalmology, and dentistry. The aim of the presented study was to find out if it is possible to ablate TMJ related structures under arthroscopic conditions. It also aims to evaluate the energy-threshold for ablation and the maximal possible rate of ablation. Contrary to other laser systems it offers a unique combination of minimal tissue alteration, precise tissue ablation guidability through optical fibers, and a good transmission through water.

  14. The effect of 193 nm excimer laser radiation on the human corneal endothelial cell density

    Energy Technology Data Exchange (ETDEWEB)

    Isager, P.; Hjortdal, J.Oe.; Ehlers, N. [Aarhus Univ. Hospital, Dept. of Ophthalmology, Aarhus (Denmark)

    1996-06-01

    The effect of 193 nm excimer laser radiation on human corneal endothelial cell density was examined. Fifty-five eyes from 35 patients underwent photorefractive keratectomy for myopia. Photomicrographs of the endothelium were taken a short time before the operation and on an average of 7 months postoperatively with a specular microscope. The average endothelial cell densities were preoperatively 3375 {+-} 266 cells/mm{sup 2} (means {+-} SD) and postoperatively 3348 {+-} 287 cells/mm{sup 2}, corresponding to a fall of 27 cells/mm{sup 2} (N = 55). This fall in endothelial cell density was not statistically significant. A significant correlation between the change in cell density and age of the patient was found, with older patients losing more cells (N = 35, 2p < 0.05). The magnification of the specular microscope was found to change with corneal thickness. The importance of correcting the endothelial cell densities for corneal thickness is discussed. (au) 14 refs.

  15. Pre-operative therapeutic eyelid hygiene in the prevention of complications following excimer laser vision correction

    Directory of Open Access Journals (Sweden)

    V. V. Kurenkov

    2012-01-01

    Full Text Available Purpose: to assess the effectiveness of pre-operative therapeutic eyelid hygiene in the prevention and treatment of dry eye and meibomian glands dysfunction following excimer laser vision surgery.Methods: In enrolled 144 patients (288 eyes, ocular surface and meibomian glands functions were evaluated before and following refractive surgery (LASIK and REIK. In pre- and post-operative period, standard ophthalmological studies were performed, including best-corrected visual acuity determination, biomicroscopy, Schirmer’s test and Norn’s test (tear break-up time. In pre-operative pe- riod, ocular surface microbial profile was assessed. Subjective symptoms of impaired tear production were revealed via questioning. In study group (70 patients, 140 eyes, therapeutic eyelid hygiene using Blefarogel 1 or Blefarogel 2 (Ltd. Heltec-Medica, Moscow, Russia was prescribed one week before surgery. In control group, no therapeutic eyelid hygiene was prescribed. All patients were received antibacterial treatment including Vigamox (Alcon, Fort Worth, tX. In both groups, Natural tears and Systane Ultra (Alcon were used as tear replacement therapy.Results: Complex treatment, including therapeutic eyelid hygiene in study group, significantly improved tear film and ocular sur- face health as well as meibomian glands functions. Inflammatory complications rate was estimated as 5.7% in study group and 10.6% in control group.Conclusion: therapeutic eyelid hygiene is highly effective in the prophylaxis and treatment of post-operative complications duу to ocular surface pathology and meibomian glands dysfunction. the procedure is safe and can be recommended as a part of complex preventive treatment before excimer laser vision correction.

  16. Pre-operative therapeutic eyelid hygiene in the prevention of complications following excimer laser vision correction

    Directory of Open Access Journals (Sweden)

    V. V. Kurenkov

    2014-07-01

    Full Text Available Purpose: to assess the effectiveness of pre-operative therapeutic eyelid hygiene in the prevention and treatment of dry eye and meibomian glands dysfunction following excimer laser vision surgery.Methods: In enrolled 144 patients (288 eyes, ocular surface and meibomian glands functions were evaluated before and following refractive surgery (LASIK and REIK. In pre- and post-operative period, standard ophthalmological studies were performed, including best-corrected visual acuity determination, biomicroscopy, Schirmer’s test and Norn’s test (tear break-up time. In pre-operative pe- riod, ocular surface microbial profile was assessed. Subjective symptoms of impaired tear production were revealed via questioning. In study group (70 patients, 140 eyes, therapeutic eyelid hygiene using Blefarogel 1 or Blefarogel 2 (Ltd. Heltec-Medica, Moscow, Russia was prescribed one week before surgery. In control group, no therapeutic eyelid hygiene was prescribed. All patients were received antibacterial treatment including Vigamox (Alcon, Fort Worth, tX. In both groups, Natural tears and Systane Ultra (Alcon were used as tear replacement therapy.Results: Complex treatment, including therapeutic eyelid hygiene in study group, significantly improved tear film and ocular sur- face health as well as meibomian glands functions. Inflammatory complications rate was estimated as 5.7% in study group and 10.6% in control group.Conclusion: therapeutic eyelid hygiene is highly effective in the prophylaxis and treatment of post-operative complications duу to ocular surface pathology and meibomian glands dysfunction. the procedure is safe and can be recommended as a part of complex preventive treatment before excimer laser vision correction.

  17. THE EXPERIENCE OF TREGALOZA BASED LUBRICANT USAGE FOR PATIENTS WHO UNDERWENT EXCIMER LASER SURGERY

    Directory of Open Access Journals (Sweden)

    E. Eskina

    2016-01-01

    Full Text Available Purpose: to evaluate the tregalose based eye drops effectiveness in patients who underwent PRK or TransPRK surgery. patients and methods: 50 patients with moderate myopia were examined before, 7 days and 1 month after PRK or TransPRK surgery made by SCHWIND Amaris excimer laser by the same surgeon. In addition to conventional diagnostics, Schirmer test and tear break up time were performed as well as ODSI questionare and Oxford index of ocular surface disorders were investigated. Patients were divided in two groups, Study group — “Thealos” group and “Control” group. In both groups patients have started using non preservative eye drops based on tregalosa and hyaluronic acid 4-th day after surgery respectively. results: The tear film breakup time was significantly better in “Thealos” group (7,22±3,61 sec 7 days postop and 9,36±3,68 sec 1 month postop in comparison to «Control” group 5,21±0,25 (р<0,01 sec and 7,21±2,85 sec respectively (р<0,05 as well as ocular surface index score in “Thealos” group post surgery was less (0,26±0,38 и 0,85±0,31 marks 7 days postop (р<0,05 and 0,09±0,19 and 0,21±0,4 (р<0,05 1 month postop respectively. There were no other statistically significant differences found in analysed data. Conclusion: Using of “Thealoz” non-preservative eye drops leads to faster recovery after surface excimer laser ablations in terms of dry eye manifestation, those as tearfilm stability and ocular surface index score, measured using “Oxford” scale. Moistening properties of tregaloze solution could be compared with those of hyaluronic acid solution.

  18. Microstructures induced by excimer laser surface melting of the SiCp/Al metal matrix composite

    Science.gov (United States)

    Qian, D. S.; Zhong, X. L.; Yan, Y. Z.; Hashimoto, T.; Liu, Z.

    2017-08-01

    Laser surface melting (LSM) was carried out on the SiCp/Al metal matrix composite (MMC) using a KrF excimer laser with a fluence of 7 J/cm2. The re-solidification microstructure was characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM) equipped with energy dispersive X-ray detector, and X-ray diffraction (XRD) analysis. It was found that a 2.5 μm thick melted layer was formed in the near-surface region, in which dissolution of the intermetallics and removal of the SiC particles occurred. The thermal and material response upon laser irradiation was simulated using three models, i.e. analytical model, finite element model (FEM) and smoothed-particle hydrodynamics (SPH) model. The effect of SiC particles on the LSM process, the mechanism of the SiC removal and the re-solidification microstructures in the melted layer were discussed. The simulation results were in good agreement with the experimental results and contributed to the generic understanding of the re-solidification microstructures induced by ns-pulsed lasers.

  19. Report on the Study of Radiation Damage in Calcium Fluoride and Magnesium Fluoride Crystals for use in Excimer Laser Applications

    Energy Technology Data Exchange (ETDEWEB)

    None, None

    1999-10-04

    A study was performed to investigate the effects of radiation damage in calcium fluoride and magnesium fluoride crystals caused by gamma rays and UV photons from excimer lasers. The purpose was to study and correlate the damage caused by these two different mechanisms in various types of material used for fabricating optical elements in high power excimer lasers and lens systems of lithography tools. These optical systems are easily damaged by the laser itself, and it is necessary to use only the most radiation resistant materials for certain key elements. It was found that a clear correlation exists between the, radiation induced damage caused by high energy gamma rays and that produced by UV photons from the excimer laser. This correlation allows a simple procedure to be developed to select the most radiation resistant material at the ingot level, which would be later used to fabricate various components of the optical system. This avoids incurring the additional cost of fabricating actual optical elements with material that would later be damaged under prolonged use. The result of this screening procedure can result in a considerable savings in the overall cost of the lens and laser system.

  20. Depth-profile investigations of triterpenoid varnishes by KrF excimer laser ablation and laser-induced breakdown spectroscopy

    Science.gov (United States)

    Theodorakopoulos, C.; Zafiropulos, V.

    2009-07-01

    The ablation properties of aged triterpenoid dammar and mastic films were investigated using a Krypton Fluoride excimer laser (248 nm, 25 ns). Ablation rate variations between surface and bulk layers indicated changes of the ablation mechanisms across the depth profiles of the films. In particular, after removal of the uppermost surface varnish layers there was a reduction of the ablation step in the bulk that was in line with a significant reduction of carbon dimer emission beneath the surface layers as detected by laser-induced breakdown spectroscopy. The results are explicable by the generation of condensation, cross-linking and oxidative gradients across the depth profile of triterpenoid varnish films during the aging degradation process, which were recently quantified and established on the molecular level.

  1. Intraoperative and early postoperative flap-related complications of laser in situ keratomileusis using two types of Moria microkeratomes.

    Science.gov (United States)

    Karabela, Yunus; Muftuoglu, Orkun; Gulkilik, Ibrahim Gokhan; Kocabora, Mehmet Selim; Ozsutcu, Mustafa

    2014-10-01

    The purpose of this study is to describe the incidence, management, and visual outcomes of intraoperative and early postoperative flap-related complications of laser in situ keratomileusis (LASIK) surgery using two types of Moria M2 microkeratomes. This retrospective analysis was performed on 806 primary LASIK cases. The intraoperative and early postoperative flap-related complications were identified and categorized according to type of Moria microkeratome. There were 52 intraoperative and early postoperative complications--one case of partial flap (0.124 %), one case of free flap (0.124 %), one case of small flap (0.124 %), 13 cases of epithelial defect (1.61 %), 12 cases of flap striae (1.49 %), 10 cases of diffuse lamellar keratitis (1.24 %), 10 cases of interface debris (1.24 %), three cases of epithelial ingrowth (0.37 %), and one case of microbial infection (0.124 %). The overall incidence of flap complications was 6.45 %. There were 27 right eye (6.73 %) and 25 left eye (6.17 %) complications. The incidence of complications with the Moria automated metallic head 130 microkeratome was 4.22 % and with the Moria single-use head 90 microkeratome was 2.23 %. We observed one culture-negative interface abscess which was cured with surgical cleaning and intensive medical treatment. The most common complication encountered was epithelial defects, followed by flap striae. Our study showed that LASIK with a microkeratome has a relatively low incidence of intraoperative and early postoperative flap complications. The authors have no financial interest in any of the issues contained in this article and have no proprietary interest in the development of marketing of or materials used in this study.

  2. Quality of vision after laser in situ keratomileusis: influence of dioptric correction and pupil size on visual function.

    Science.gov (United States)

    Lee, Yuan-Chieh; Hu, Fung-Rong; Wang, I-Jong

    2003-04-01

    To determine the influence of pupil size and the amount of ablation on visual performance and on the patient's perception of glare or halo after laser in situ keratomileusis (LASIK). Department of Ophthalmology, National Taiwan University Hospital, Taipei, Taiwan. This study included a random cross-section of 50 eyes of 32 patients with "uniform" topography at least 6 months after LASIK and 51 eyes of 28 patients who had normal corneas. Each LASIK patient completed a survey rating adverse effects such as symptoms of night glare and halo. Pupil diameter and best spectacle-corrected visual acuity (BSCVA) were measured under photopic and scotopic conditions. Contrast sensitivity was measured with an MCT 8000 (Vistech Consultants, Inc.) under daytime and nighttime and with night glare conditions. A Technomed C-scan (Technomed Technology) was performed, and the potential corneal visual acuity (PCVA) was calculated after the settings for the pupil size were changed to the values measured under bright-light or dim-light conditions. No significant difference was found between the post-LASIK and normal cornea groups in photopic or scotopic BSCVA (P>.05). In cases of moderate myopia, the post-LASIK group had decreased PCVA and contrast sensitivity (P.05). Pupil size was not significantly correlated with glare or halo symptoms, BSCVA, or contrast sensitivity under scotopic or photopic conditions (P>.05). In moderate myopia, the amount of attempted correction of the spherical equivalent (SE) was correlated with halo symptoms (PPupil size was not significantly correlated with glare or halo symptoms, BSCVA, or contrast sensitivity in post-LASIK patients with "uniform" topography who had scotopic pupils not larger than 7.0 mm.

  3. Referrals to the Wills Eye Institute Cornea Service after laser in situ keratomileusis: reasons for patient dissatisfaction.

    Science.gov (United States)

    Levinson, Brett A; Rapuano, Christopher J; Cohen, Elisabeth J; Hammersmith, Kristin M; Ayres, Brandon D; Laibson, Peter R

    2008-01-01

    To review the symptoms, findings, and management options in patients referred to the Cornea Service who were unsatisfied with results after laser in situ keratomileusis (LASIK). Cornea Service, Wills Eye Institute, Philadelphia, Pennsylvania, USA. A retrospective chart review was conducted of all patients seen for consultation between January 1, 2004, and December 31, 2006, who had LASIK performed elsewhere. The parameters extracted were demographic data, history, symptoms, postoperative best corrected and uncorrected visual acuities, surgical complications, examination findings, and treatment recommendations. The data were also compared with previously unpublished data collected at Wills Eye from 1998 to 2003. One hundred fifty-seven eyes of 109 patients seen in consultation after LASIK were identified. Twenty-eight percent were referred by the LASIK surgeon and 54%, by another eye doctor; 17% were self-referred. The most common chief complaints were poor distance vision (63%), dry eyes (19%), redness/pain (7%), and glare and halos (5%). Forty-four eyes (28%) had surgical complications or enhancements. The most common diagnoses were dry eye or blepharitis (27.8%), irregular astigmatism (12.1%), and epithelial ingrowth (9.1%). Eleven percent were referred in the first month after LASIK; 23% and 10% were referred between 1 and 6 months and 7 and 12 months, respectively. Medical management (eg, artificial tears, steroids, other dry-eye treatment) was offered in 39% of cases, surgical intervention in 27%, and observation only in 7%. Nonsurgical therapy was offered in 73% of cases. Most patients who came for consultation were referred by a doctor other than their LASIK surgeon. Poor distance vision, dry eye, redness/pain, and glare and halos were the most common chief complaints and dry eye or blepharitis, irregular astigmatism, and epithelial ingrowth, the most common diagnoses.

  4. New algorithm for intraocular lens power calculations after myopic laser in situ keratomileusis based on rotating Scheimpflug camera data.

    Science.gov (United States)

    Potvin, Richard; Hill, Warren

    2015-02-01

    To develop an algorithm to calculate intraocular lens (IOL) power for eyes with previous laser in situ keratomileusis (LASIK) for myopia based on data from a rotating Scheimpflug camera and to compare calculations with those of current formulas. East Valley Ophthalmology, Mesa, Arizona, USA. Observational case series. Relevant IOL calculation and postoperative refractive data were obtained for eyes of patients who had previous myopic LASIK and subsequent cataract surgery. Initial screening and correlation analysis identified Pentacam Scheimpflug keratometry (K) values appropriate for use in calculating a "best K" for IOL power calculations in these eyes. Error analysis identified other eye measures to improve results. Final results were compared with results from 9 other calculation methods available on the American Society of Cataract and Refractive Surgery (ASCRS) web site. The study obtained data from 101 eyes of 77 patients. More than 200 Scheimpflug K-formula combinations were evaluated for each eye. The true net power in the 4.0 mm zone centered on the corneal apex provided the best adjusted K reading for IOL power calculation in the Shammas no-history formula. The final formula had good outcomes, with 34%, 66%, and 91% of eyes being within ±0.25 diopter (D), ±0.50 D, and ±1.00 D of the refractive target, respectively. These results compare favorably to the best formulas on the ASCRS web site. The no-history formula derived using the Scheimpflug device's true net power in the 4.0 mm zone centered on the corneal apex appears to be an accurate method for determining IOL power after LASIK for myopia. Corroboration with additional data sets is suggested. Neither author has a financial or proprietary interest in any material or method mentioned. Copyright © 2015 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  5. Increased preference of surface ablation over laser in situ keratomileusis between 2008–2011 is correlated to risk of ecatasia

    Directory of Open Access Journals (Sweden)

    Moisseiev E

    2013-01-01

    Full Text Available Elad Moisseiev,1,3 Tzahi Sela,2 Liza Minkev,2 David Varssano1,31Department of Ophthalmology, Tel-Aviv Medical Center, Tel-Aviv, Israel; 2Care Vision, Tel Aviv, Israel; 3Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, IsraelPurpose: To evaluate the trends in corneal refractive procedure selection for the correction of myopia, focusing on the relative proportions of laser in situ keratomileusis (LASIK and surface ablation procedures.Methods: Only eyes that underwent LASIK or surface ablation for the correction of myopia between 2008–2011 were included in this retrospective study. Additional recorded parameters included patient age, preoperative manifest refraction, corneal thickness, and calculated residual corneal bed thickness. A risk score was given to each eye, based on these parameters, according to the Ectasia Risk Factor Score System (ERFSS, without the preoperative corneal topography.Results: This study included 16,163 eyes, of which 38.4% underwent LASIK and 61.6% underwent surface ablation. The risk score correlated with procedure selection, with LASIK being preferred in eyes with a score of 0 and surface ablation in eyes with a score of 2 or higher. When controlling for age, preoperative manifest refraction, corneal thickness, and all parameters, the relative proportion of surface ablation compared with LASIK was found to have grown significantly during the study period.Conclusions: Our results indicate that with time, surface ablation tended to be performed more often than LASIK for the correction of myopia in our cohort. Increased awareness of risk factors and preoperative risk assessment tools, such as the ERFSS, have shifted the current practice of refractive surgery from LASIK towards surface ablation despite the former's advantages, especially in cases in which the risk for ectasia is more than minimal (risk score 2 and higher.Keywords: surface ablation, LASIK, PRK, myopia correction, ectasia

  6. Confocal comparison of corneal reinnervation after small incision lenticule extraction (SMILE and femtosecond laser in situ keratomileusis (FS-LASIK.

    Directory of Open Access Journals (Sweden)

    Meiyan Li

    Full Text Available PURPOSE: To evaluate corneal reinnervation, and the corresponding corneal sensitivity and keratocyte density after small incision lenticule extraction (SMILE and femtosecond laser in situ keratomileusis (FS-LASIK. METHODS: In this prospective, non-randomized observational study, 18 patients (32 eyes received SMILE surgery, and 22 patients (42 eyes received FS-LASIK surgery to correct myopia. The corneal subbasal nerve density and microscopic morphological changes in corneal architecture were evaluated by confocal microscopy prior to surgery and at 1 week, 1 month, 3 months, and 6 months after surgery. A correlation analysis was performed between subbasal corneal nerve density and the corresponding keratocyte density and corneal sensitivity. RESULTS: The decrease in subbasal nerve density was less severe in SMILE-treated eyes than in FS-LASIK-treated eyes at 1 week (P = 0.0147, 1 month (P = 0.0243, and 3 months (P = 0.0498, but no difference was detected at the 6-month visit (P = 0.5277. The subbasal nerve density correlated positively with central corneal sensitivity in both groups (r = 0.416, P<0.0001, and r = 0.2567, P = 0.0038 for SMILE group and FS-LASIK group, respectively. The SMILE-treated eyes have a lower risk of developing peripheral empty space with epithelial cells filling in (P = 0.0005. CONCLUSIONS: The decrease in subbasal nerve fiber density was less severe in the SMILE group than the FS-LASIK group in the first 3 months following the surgeries. The subbasal nerve density was correlated with central corneal sensitivity.

  7. Comparison of 5468 retreatments after laser in situ keratomileusis by lifting the flap or performing photorefractive keratectomy on the flap.

    Science.gov (United States)

    Ortega-Usobiaga, J; Llovet-Osuna, F; Katz, T; Djodeyre, M R; Druchkiv, V; Bilbao-Calabuig, R; Baviera, J

    2017-06-23

    To assess visual outcomes of retreatment after laser in situ keratomileusis (LASIK) by lifting the flap or performing photorefractive keratectomy (PRK) on the flap, as well as to establish whether there was an increased risk of epithelial ingrowth (EIG) when LASIK and lifting of the flap are separated by a long time interval and to determine the incidence of corneal haze after PRK. Retrospective study of 4077 patients (5468 eyes) who underwent LASIK and subsequent retreatment were reviewed in order to study their visual results and identify cases of EIG and corneal haze. Enhancements included 5196 eyes from 3876 patients that were retreated by lifting the flap, and 272 eyes from 201 patients that were retreated by PRK on the flap. No statistically significant differences were found between the retreatments in terms of predictability, efficacy, and safety. A total of 704 cases of EIG were found after lifting the flap, for which surgical cleansing was necessary in 70. Surgical cleansing decreased the efficacy index when compared with patients with EIG who did not need cleansing (P=.01). Differences in terms of safety and predictability were not statistically significant. The incidence of corneal haze after ablation of the surface of the previous flap was 14.34%, although none of these cases were clinically relevant. Visual outcomes were similar between patients who were retreated by lifting the flap and those who underwent PRK. The incidence of EIG when the flap was lifted was 13.55%. The incidence of EIG increases with the time elapsed between the primary procedure and retreatment. Copyright © 2017 Sociedad Española de Oftalmología. Publicado por Elsevier España, S.L.U. All rights reserved.

  8. Excimer laser texturing of natural composite polymer surfaces for studying cell-to-substrate specific response

    Energy Technology Data Exchange (ETDEWEB)

    Dinca, V., E-mail: dincavalentina@yahoo.com [NILPRP, National Institute for Lasers, Plasma and Radiation Physics, Magurele, Bucharest (Romania); Alloncle, P.; Delaporte, P. [Aix-Marseille University, CNRS, LP3 Laboratory, Campus de Luminy, 13288 Marseille (France); Ion, V. [NILPRP, National Institute for Lasers, Plasma and Radiation Physics, Magurele, Bucharest (Romania); Faculty of Physics, University of Bucharest, 077125 Magurele (Romania); Rusen, L.; Filipescu, M. [NILPRP, National Institute for Lasers, Plasma and Radiation Physics, Magurele, Bucharest (Romania); Mustaciosu, C. [Horia Hulubei National Institute of Physics and Nuclear Engineering – IFIN HH, Magurele, Bucharest (Romania); Luculescu, C.; Dinescu, M. [NILPRP, National Institute for Lasers, Plasma and Radiation Physics, Magurele, Bucharest (Romania)

    2015-10-15

    Highlights: • Roughness gradients are obtained in one step by applying single laser pulses and sample tilting. • BSA protein and cell dependence behavior onto gradient characteristics was studied. • The degradation of the samples by lysozyme was correlated to its ability to access the textured area. - Abstract: Surface modifications of biocompatible materials are among the main factors used for enhancing and promoting specific cellular activities (e.g. spreading, adhesion, migration, and differentiation) for various types of medical applications such as implants, microfluidic devices, or tissue engineering scaffolds. In this work an excimer laser at 193 nm was used to fabricate chitosan–collagen roughness gradients. The roughness gradients were obtained in one step by applying single laser pulses and sample tilting. Fourier transform infrared spectroscopy measurements, atomic force microscopy (AFM), scanning electron microscopy (SEM), and spectro-ellipsometry (SE) were used for sample characterization. The goal is to determine the optimal morpho-chemical characteristics of these structures for in vitro tailoring of protein adsorption and cell behavior. The response induced by the roughness gradient onto various cell lines (i.e. L 929 fibroblasts, HEP G2 hepatocytes, OLN 93 oligodendrocytes, M63 osteoblasts) and bovine serum albumin (BSA) protein absorption was investigated.

  9. Film forming properties of silicon nanoparticles on SixNy coated substrates during excimer laser annealing

    Science.gov (United States)

    Caninenberg, M.; Kiesler, D.; Benson, N.; Schmechel, R.

    2017-05-01

    In this article we investigate the film forming properties of excimer laser annealed silicon nanoparticles on non-silicon substrates. In contrast to their film forming properties on oxide free silicon substrates, the nanoparticle thin film tends to dewet and form a porous μ-structure on the silicon nitrite covered glass model substrates considered for our investigation. This is quantified using a SEM study in conjunction with image processing software, in order to evaluate the μ-structure size and inter μ-structure distance in dependence of the laser energy density. To generalize our results, the film forming process is described using a COMSOL Multiphysics ® fluid dynamics model, which solves the Navier Stokes equation for incompressible Newtonian fluids. To account for the porous nanoparticle thin film structure in the simulation, an effective medium approach is used by applying a conservative level set one phase method to our mesh. This effort allows us to predict the Si melt film formation ranging from a porous Si μ-structure to a compact 100% density Si thin film in dependence of the substrate / thin film interaction, as well as the laser energy used for the nanoparticle processing.

  10. The effect on the ultrastructure of dental enamel of excimer-dye, argon-ion and CO2 lasers.

    Science.gov (United States)

    Palamara, J; Phakey, P P; Orams, H J; Rachinger, W A

    1992-12-01

    This study aimed to investigate the ultrastructural changes that occur in dental enamel irradiated with pulsed excimer-dye, continuous-wave (CW) argon-ion and CW CO2 lasers. The pulsed excimer-dye laser produced deep craters, rough damaged surfaces with underlying porosity and amorphous vitrified material. The vitrification of the enamel indicated that the temperature in these areas must have been at least in the range 1280 to 1600 degrees C. The CW argon-ion laser irradiation produced a changed non-cratered surface with inter-crystalline porosity and a mixture of small and some large irregularly packed recrystallized enamel crystals. The CW CO2 laser produced shallow craters, surface crazing and lifting off the removal of the surface layer to expose the underlying roughened enamel. The ultrastructure revealed inter- and intra-crystalline porosity, a mixture of small but variable size irregularly packed recrystallized enamel crystals and also well packed large crystals which indicated further grain growth. The porosity in lased enamel was overall very similar to that seen in enamel heated in an electric furnace to a temperature of 600 degrees C. The presence of recrystallized enamel crystals indicated a temperature rise of approximately 1000 degrees C and the grain growth indicated that a temperature > or = 1000 degrees C existed for some time after the laser irradiation. In general the excimer-dye laser produced most surface destruction because of its higher power density and shorter interaction time and the argon-ion laser produced least damage. These results indicated that the lasers used in this study require much more refinement before they can find therapeutic application to dental enamel, and this may well be the case for other lasers being investigated for clinical dental practise.

  11. Krypton Gas for High Quality Single Wall Carbon Nanotubes Synthesis by KrF Excimer Laser Ablation

    Directory of Open Access Journals (Sweden)

    Jasim Al-Zanganawee

    2015-01-01

    Full Text Available We report for the first time the production of single wall carbon nanotubes (SWCNTs by KrF excimer laser ablation method under the krypton gas atmosphere. For the ablation experiment 450 mJ energy and 30 Hz repetition rate KrF excimer laser was used, and the target was prepared with the following composition: 0.6% Ni, 0.6% Co, and 98.8% C (atomic percentage. The ablation product was characterized by confocal Raman microspectroscopy, transmission electron microscopy (TEM, scanning electron microscopy (SEM, and thermogravimetric analysis (TGA. The SWCNTs obtained are a mixture of semiconducting and metallic types with narrow diameters distribution of 1.26 to 1.49 nm, are micrometers long, and contain low amount of graphite and amorphous carbon.

  12. Des lasers à excimères pour cristalliser le silicium des écrans plats : pourquoi ? comment ?

    Science.gov (United States)

    Prat, C.

    2003-06-01

    Les contraintes techniques et économiques de la fabrication d'écrans plats à cristaux liquides à matrice active ont suscité de nombreuses études de procédés de cristallisation de couches minces de silicium par laser à excimères, exploitant principalement trois types de phénomènes physiques, dans le but d'obtenir des cristaux micrométriques les plus uniformes possible.

  13. Wettability characteristics of carbon steel modified with CO2, Nd:YAG, Excimer and high power diode lasers

    OpenAIRE

    Lawrence, Jonathan; Li, Lin

    2000-01-01

    Interaction of CO2, Nd:YAG, excimer and high power diode laser (HPDL) radiation with the surface of a common mild steel (EN8) was found to effect changes in the wettability characteristics of the steel, namely changes in the measured contact angle. These modifications are related to changes in the surface roughness, changes in the surface oxygen content and changes in the surface energy of the mild steel. The wettability characteristics of the selected mild steel could be controll...

  14. Excimer laser doping technique for application in an integrated CdTe imaging device

    CERN Document Server

    Mochizuki, D; Aoki, T; Tomita, Y; Nihashi, T; Hatanaka, Y

    1999-01-01

    CdTe is an attractive semiconductor material for applications in solid-state high-energy X-ray and gamma-ray imaging systems because of its high absorption coefficient, large band gap, good mobility lifetime product of holes and stability at normal atmospheric conditions. We propose a new concept for fabricating an integrated CdTe with monolithic circuit configuration for two-dimensional imaging systems suitable for medical, research or industrial applications and operation at room temperature. A new doping technique has been recently developed that employs excimer laser radiation to diffuse impurity atoms into the semiconductor. Accordingly, heavily doped n- and p-type layers with resistivities less than 1 OMEGA cm can be formed on the high resistive CdTe crystals. We have further extended this technique for doping with spatial pattern. We will present the laser doping technique and various results thus obtained. Spatially patterned doping is demonstrated and we propose the use of these doping techniques for...

  15. Excimer laser assisted very fast exfoliation and reduction of graphite oxide at room temperature under air ambient for Supercapacitors electrode

    Science.gov (United States)

    Malek Hosseini, S. M. B.; Baizaee, S. M.; Naderi, Hamid Reza; Dare Kordi, Ali

    2018-01-01

    Excimer laser was used for reduction and exfoliation of graphite oxide (GO) at room temperature under air ambient. The prepared excimer laser reduced graphite oxide (XLRGO) is characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), nitrogen adsorption/desorption (BET method), X-ray diffraction (XRD), X-ray photoemission spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and UV-vis absorption techniques for surface, structural functional groups and band gap analysis. Electrochemical properties are investigated using cyclic voltammetry, galvanostatic charge-discharge, electrochemical impedance spectroscopy (EIS) and continues cyclic voltammetry (CCV) in 0.5 M Na2SO4 as electrolyte. Electrochemical investigations revealed that XLRGO electrode has enhanced supercapacitive performance including specific capacitance of 299 F/g at a scan rate of 2 mV/s. Furthermore, CCV measurement showed that XLRGO electrode kept 97.8% of its initial capacitance/capacity after 4000 cycles. The obtained results from electrochemical investigations confirm that the reduction of GO by using an excimer laser produces high-quality graphene for supercapacitor applications without the need for additional operations.

  16. Combined Excimer Laser Photoablation and Amniotic Membrane Overlay for Relief of Symptomatic Discomfort in Gelatinous Drop-like Corneal Dystrophy.

    Science.gov (United States)

    Alex, Anne F; Eter, Nicole; Uhlig, Constantin E

    2015-10-01

    To describe the efficacy of combined excimer laser photoablation and amniotic overlay membrane in the relief of symptomatic discomfort in a 17-year-old patient who had gelatinous drop-like corneal dystrophy. The best-corrected visual acuity (BCVA) was measured with Snellen letters. Slit-lamp examination of the ocular surface and anterior chamber was performed at baseline. Results were photodocumented. Excimer laser photoablation was performed and subsequently 2 amniotic membranes were transconjunctivally fixated with 10.0 nylon sutures. Investigations and documentation were performed at baseline, every 2 months in the first year, and then every 6 months. The duration of follow-up was 22 months. At baseline, the BCVA was 20/70 in the right eye and 20/200 in the left eye. The patient reported distinct photophobia. Slit-lamp examination was difficult because of blepharospasm. Although gelatinous drops developed again and the BCVA decreased to 2/200, the patient reported significant relief after both microsurgical treatments and remained comfortable at 20 and 22 months. Excimer laser photocoagulation combined with amniotic membrane overlay does not stop the development of gelatinous drop-like corneal dystrophy but may improve subjective comfort. Such treatment does not hinder subsequent lamellar or penetrating grafts and is helpful in providing the necessary time for preparation of matched keratoplasties.

  17. Comparison of the corneal biomechanical effects after small-incision lenticule extraction and Q value guided femtosecond laser-assisted laser in situ keratomileusis

    Directory of Open Access Journals (Sweden)

    Jun Zhang

    2016-04-01

    Full Text Available AIM:By comparing the changes of biomechanical properties of the cornea after small-incision lenticule extraction(SMILEand those after Q value guided femtosecond laser-assisted laser in situ keratomileusis(FSLASIK, to study the stability of biomechanical properties of the cornea after these two kinds of surgery and provide objective data for clinical operation.METHODS: Prospective comparative cases. One hundred and two cases(200 eyeswith myopia and myopic astigmatism were divided into 2 groups, 51 cases(100 eyesfor SMILE, and 51 cases(100 eyesfor Q value guided FS-LASIK. Corneal hysteresis(CHand the corneal resistance factor(CRFwere quantitatively assessed with the Ocular Response Analyzer(ORApreoperatively and 1d, 2wk, 1 and 3mo postoperatively.RESULTS: The decrease in CH and the CRF were statistically significant in both groups(PP>0.05. There were no statistically significant differences between the biomechanical changes in the two groups at any time(P>0.05.CONCLUSION: Both SMILE and Q value guided FS-LASIK can cause biomechanical decreases in the cornea. After 1d postoperatively, the decreases are nearly stable. There are no significant differences between the effect of SMILE and Q value guided FS-LASIK on the biomechanical properties of the cornea.

  18. Comparison of wavefront aberration changes in the anterior corneal surface after laser-assisted subepithelial keratectomy and laser in situ keratomileusis: preliminary study.

    Science.gov (United States)

    Buzzonetti, Luca; Iarossi, Giancarlo; Valente, Paola; Volpi, Marzia; Petrocelli, Gianni; Scullica, Luigi

    2004-09-01

    To compare changes in anterior corneal wavefront aberrations after myopic laser-assisted subepithelial keratectomy (LASEK) and laser in situ keratomileusis (LASIK). Institute of Ophthalmology, Catholic University, Rome, Italy. This prospective study included 36 eyes of 25 myopic patients: 18 eyes of 12 patients had LASEK and 18 eyes of 13 patients, LASIK. The topography data (CSO EyeMap, version 6.2) were used to calculate corneal aberrations with 3.0 mm and 7.0 mm pupils before and 3 months after surgery. Total corneal aberrations increased similarly after LASEK and LASIK with the 7.0 mm pupil but did not change with the 3.0 mm pupil. Coma-like and spherical-like aberrations changed similarly after both procedures, but spherical-like aberrations increased after LASEK with the 3.0 mm pupil (P.05, independent t test), in individual eyes with an achieved correction less than 7.50 diopters (D), spherical-like aberrations increased more after LASEK than after LASIK. In this preliminary study, myopic LASEK and LASIK changed total and higher-order corneal aberrations. In both procedures, changes in spherical-like aberrations were dependent on the achieved correction. However, in individual eyes, spherical-like aberrations increased more after LASEK than after LASIK for low-moderate achieved correction, suggesting that these procedures may induce the same optical changes in the anterior corneal surface in different ways.

  19. Microstructures induced by excimer laser surface melting of the SiC{sub p}/Al metal matrix composite

    Energy Technology Data Exchange (ETDEWEB)

    Qian, D.S., E-mail: Daishu.qian@postgrad.manchester.ac.uk; Zhong, X.L.; Yan, Y.Z.; Hashimoto, T.; Liu, Z.

    2017-08-01

    Highlights: • Microstructural analysis of the excimer laser-melted SiC{sub p}/AA2124;. • Analytical, FEM, and SPH simulation of the laser-material interaction;. • Mechanism of the formation of the laser-induced microstructure. - Abstract: Laser surface melting (LSM) was carried out on the SiC{sub p}/Al metal matrix composite (MMC) using a KrF excimer laser with a fluence of 7 J/cm{sup 2}. The re-solidification microstructure was characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM) equipped with energy dispersive X-ray detector, and X-ray diffraction (XRD) analysis. It was found that a 2.5 μm thick melted layer was formed in the near-surface region, in which dissolution of the intermetallics and removal of the SiC particles occurred. The thermal and material response upon laser irradiation was simulated using three models, i.e. analytical model, finite element model (FEM) and smoothed-particle hydrodynamics (SPH) model. The effect of SiC particles on the LSM process, the mechanism of the SiC removal and the re-solidification microstructures in the melted layer were discussed. The simulation results were in good agreement with the experimental results and contributed to the generic understanding of the re-solidification microstructures induced by ns-pulsed lasers.

  20. Influence of corneal collagen crosslinking with riboflavin and ultraviolet-a irradiation on excimer laser surgery.

    Science.gov (United States)

    Kampik, Daniel; Ralla, Bernhard; Keller, Sabine; Hirschberg, Markus; Friedl, Peter; Geerling, Gerd

    2010-08-01

    Riboflavin/ultraviolet A (UVA) cross-linking (CXL) of corneal collagen is a novel method of stabilizing corneal mechanical properties and preventing progression of keratectasias. This study was conducted to investigate whether CXL influences ablation rate, flap thickness, and refractive results of excimer laser procedures ex vivo. Corneal epithelium was removed from enucleated porcine eyes, and CXL was performed with riboflavin 0.1% and UVA radiation (365 nm, 3 mW/cm(2)) for 30 minutes. Control eyes received epithelial abrasion only. Diffusion of riboflavin through the cornea was assessed by using infrared-excited, two-photon microscopy of riboflavin autofluorescence, combined with second-harmonic generation of fibrillar collagen. During phototherapeutic keratectomy, corneal thickness was measured by optical coherence pachymetry. During LASIK for myopia, the flap thickness of microkeratome cuts was measured and the induced refractive change assessed by Placido topography. Data were analyzed by Shapiro-Wilk test and Student's t-test. Multiphoton imaging showed a rapid (30-minute) and even distribution of riboflavin throughout the corneal stroma. No difference in ablation rate was measured in treated and untreated corneas (P = 0.90). Mean flap thickness was increased by 44% in cross-linked corneas (P refractive change was reduced in CXL-treated eyes by 20.1% (P refractive change after LASIK for myopia. Although the laser ablation rate is unaffected, CXL results in an increased flap thickness. This study suggests the need for adjustment of microkeratome and laser parameters for LASIK after CXL and indirectly endorses the theory of a direct stiffening effect of CXL.

  1. Development of a Silicon Based Electron Beam Transmission Window for Use in a KrF Excimer Laser System

    CERN Document Server

    Gentile, C A; Hartfield, J W; Hawryluk, R J; Hegeler, F; Heitzenroeder, P J; Jun, C H; Ku, L P; Lamarche, P H; Myers, M C; Parker, J J; Parsells, R F; Payen, M; Raftopoulos, S; Sethian, J D

    2002-01-01

    The Princeton Plasma Physics Laboratory (PPPL), in collaboration with the Naval Research Laboratory (NRL), is currently investigating various novel materials (single crystal silicon, , and ) for use as electron-beam transmission windows in a KrF excimer laser system. The primary function of the window is to isolate the active medium (excimer gas) from the excitation mechanism (field-emission diodes). Chosen window geometry must accommodate electron energy transfer greater than 80% (750 keV), while maintaining structural integrity during mechanical load (1.3 to 2.0 atm base pressure differential, approximate 0.5 atm cyclic pressure amplitude, 5 Hz repetition rate) and thermal load across the entire hibachi area (approximate 0.9 W centre dot cm superscript ''-2''). In addition, the window must be chemically resistant to attack by fluorine free-radicals (hydrofluoric acid, secondary). In accordance with these structural, functional, and operational parameters, a 22.4 mm square silicon prototype window, coated w...

  2. Results of excimer laser photorefractive keratectomy for the correction of myopia at Cedars-Sinai Medical Center: 1993

    Science.gov (United States)

    Maguen, Ezra I.; Salz, James J.; Nesburn, Anthony B.; Warren, Cathy; Macy, Jonathan I.; Papaioannou, Thanassis; Hofbauer, John; Berlin, Michael S.

    1994-06-01

    This report summarizes the authors' 3-year experience with excimer laser photorefractive keratectomy (PRK) on 240 eyes of 161 patients. With constant laser emission parameters, nitrogen (N2) flow across the cornea was used on 79 eyes while 161 eyes had no N2 flow. 74 eyes were operated on without fixation with a suction ring. Postoperative pain management included patching and oral analgesics in 77 eyes and the use of topical Diclofenac or Ketorolac, and a therapeutic soft contact lens in 163 eyes. Follow up ranged from 1 month (206 eyes) to 36 months (10 eyes).

  3. Terraced copper growth deposited onto Teflon AF1600 by the excimer laser irradiation of Cu(hfac)TMVS

    Energy Technology Data Exchange (ETDEWEB)

    Popovici, D.; Piyakis, K.; Sacher, E.; Meunier, M. [Ecole Polytechnique, Montreal, Quebec (Canada)

    1996-12-31

    The authors are studying the feasibility of constructing Cu/fluoropolymer multilayer devices, in an effort to reduce both metal R and insulator C, a necessary condition in VLSI and GSI microelectronic applications. The laser chemical vapor deposition (LCVD) of the organometallic precursor Cu(hfac)TMVS (hexafluoroacetylacetonate)(trimethylvinylsilane) is used to grow copper films on a Teflon AF1600 substrate. Exposure to excimer laser radiation at 248 nm results in a terraced copper growth. A simple model, based on interference effects in the Teflon and copper layers, is presented to account for this structure.

  4. Hydroxyapatite and bioactive glass surfaces for fiber reinforced composite implants via surface ablation by Excimer laser.

    Science.gov (United States)

    Kulkova, Julia; Moritz, Niko; Huhtinen, Hannu; Mattila, Riina; Donati, Ivan; Marsich, Eleonora; Paoletti, Sergio; Vallittu, Pekka K

    2017-11-01

    In skeletal reconstructions, composites, such as bisphenol-A-glycidyldimethacrylate resin reinforced with glass fibers, are potentially useful alternatives to metallic implants. Recently, we reported a novel method to prepare bioactive surfaces for these composites. Surface etching by Excimer laser was used to expose bioactive glass granules embedded in the resin. The purpose of this study was to analyze two types of bioactive surfaces created by this technique. The surfaces contained bioactive glass and hydroxyapatite granules. The selected processing parameters were adequate for the creation of the surfaces. However, the use of porous hydroxyapatite prevented the complete exposure the granules. In cell culture, for bioactive glass coatings, the pattern of proliferation of MG63 cells was comparable to that in the positive control group (Ti6Al4V) while inferior cell proliferation was observed on the surfaces containing hydroxyapatite granules. Scanning electron microscopy revealed osteointegration of implants with both types of surfaces. The technique is suitable for the exposure of solid bioactive glass granules. However, the long-term performance of the surfaces needs further assessment. Copyright © 2017 Elsevier Ltd. All rights reserved.

  5. Excimer laser phototherapeutic keratectomy for the treatment of clinically presumed fungal keratitis.

    Science.gov (United States)

    Li, Liang-Mao; Zhao, Li-Quan; Qu, Ling-Hui; Li, Peng

    2014-01-01

    This retrospective study was to evaluate treatment outcomes of excimer laser phototherapeutic keratectomy (PTK) for clinically presumed fungal keratitis. Forty-seven eyes of 47 consecutive patients underwent manual superficial debridement and PTK. All corneal lesions were located in the anterior stroma and were resistant to medication therapy for at least one week. Data were collected by a retrospective chart review with at least six months of follow-up data available. After PTK, infected corneal lesions were completely removed and the clinical symptoms resolved in 41 cases (87.2%). The mean ablation depth was 114.39 ± 45.51  μ m and diameter of ablation was 4.06 ± 1.07 mm. The mean time for healing of the epithelial defect was 8.8 ± 5.6 days. Thirty-four eyes (82.9%) showed an improvement in best spectacle-corrected visual acuity of two or more lines. PTK complications included mild to moderate corneal haze, hyperopic shift, irregular astigmatism, and thinning cornea. Six eyes (12.8%) still showed progressed infection, and conjunctival flap covering, amniotic membrane transplantation, or penetrating keratoplasty were given. PTK is a valuable therapeutic alternative for superficial infectious keratitis. It can effectively eradicate lesions, hasten reepithelialization, and restore and preserve useful visual function. However, the selection of surgery candidates should be conducted carefully.

  6. Intraoperative videokeratography in penetrating keratoplasty and excimer laser-assisted lamellar keratoplasty for keratoconus.

    Science.gov (United States)

    Spadea, Leopoldo; Fiasca, Arianna; Federici, Simone

    2010-09-01

    To evaluate the usefulness of intraoperative computerized corneal topographic data in excimer laser-assisted lamellar keratoplasty (ELLK) and penetrating keratoplasty (PK). Prospective, comparative, interventional case series. Intra- and postoperative videokeratography (Keratron Scout) evaluation was performed on 30 eyes of 30 consecutive patients affected by keratoconus (16 men and 14 women; mean age 32.63±8.02 years) submitted to ELLK (15 eyes) using 16 interrupted 10-0 nylon stitches or to PK (15 eyes) using a 12-bite 10-0 nylon double-running continuous suture. In the ELLK group, the mean intraoperative keratometric astigmatism was 12.06±4.86 diopters (D), which changed to 5.19±2.51 D after topography-guided intraoperative suture adjustment. In the PK group, intraoperative keratometric astigmatism was 10.18±3.88 D, which changed to 3.49±0.41 D. After 24 months (sutures out), the mean videokeratographic keratometric astigmatism was 3.35±1.96 D in the ELLK group and 3.37±0.92 D in the PK group. The Alpins method of vector analysis showed some significant changes especially in the ELLK group. In keratoplasty surgery, videokeratography is useful for suture adjustment. In the PK group, using a double-running suture technique, the postoperative astigmatism (after all sutures were removed) was similar to the astigmatism measured intraoperatively by videokeratography. Copyright 2010, SLACK Incorporated.

  7. Insight into excimer laser crystallization exploiting ellipsometry: Effect of silicon film precursor

    Energy Technology Data Exchange (ETDEWEB)

    Losurdo, Maria [Institute of Inorganic Methodologies and of Plasmas, IMIP-CNR and INSTM sez. Bari, Via Orabona 4, 70125 Bari (Italy)], E-mail: maria.losurdo@ba.imip.cnr.it; Giangregorio, Maria M.; Sacchetti, Alberto; Capezzuto, Pio; Bruno, Giovanni [Institute of Inorganic Methodologies and of Plasmas, IMIP-CNR and INSTM sez. Bari, Via Orabona 4, 70125 Bari (Italy); Mariucci, Luigi; Fortunato, Guglielmo [IFN-CNR, Via Cineto Romano, 42 - 00156 Rome (Italy)

    2007-07-16

    The optical diagnostic of spectroscopic ellipsometry is shown to be an effective tool to investigate the mechanism of excimer laser crystallization (ELC) of silicon thin films. A detailed spectroscopic ellipsometric investigation of the microstructures of polycrystalline Si films obtained on SiO{sub 2}/Si wafers by ELC of a-Si:H and nc-Si films deposited, respectively, by SiH{sub 4} plasma enhanced chemical vapor deposition (PECVD) and SiF{sub 4}-PECVD is presented. It is shown that ellipsometric spectra of the pseudodielectric function of polysilicon thin films allows to discern the three different ELC regimes of partial melting, super lateral growth and complete melting. Exploiting ellipsometry and atomic force microscopy, it is shown that ELC of nc-Si has very low energy density threshold of 95 mJ/cm{sup 2} for complete melting, and that re-crystallization to large grains of {approx} 2 {mu}m can be achieved by multi-shot irradiation at an energy density as low as 260 mJ/cm{sup 2} when using nc-Si when compared to 340 mJ/cm{sup 2} for the ELC of a-Si films.

  8. Excimer Laser Phototherapeutic Keratectomy for the Treatment of Clinically Presumed Fungal Keratitis

    Directory of Open Access Journals (Sweden)

    Liang-Mao Li

    2014-01-01

    Full Text Available This retrospective study was to evaluate treatment outcomes of excimer laser phototherapeutic keratectomy (PTK for clinically presumed fungal keratitis. Forty-seven eyes of 47 consecutive patients underwent manual superficial debridement and PTK. All corneal lesions were located in the anterior stroma and were resistant to medication therapy for at least one week. Data were collected by a retrospective chart review with at least six months of follow-up data available. After PTK, infected corneal lesions were completely removed and the clinical symptoms resolved in 41 cases (87.2%. The mean ablation depth was 114.39±45.51 μm and diameter of ablation was 4.06±1.07 mm. The mean time for healing of the epithelial defect was 8.8±5.6 days. Thirty-four eyes (82.9% showed an improvement in best spectacle-corrected visual acuity of two or more lines. PTK complications included mild to moderate corneal haze, hyperopic shift, irregular astigmatism, and thinning cornea. Six eyes (12.8% still showed progressed infection, and conjunctival flap covering, amniotic membrane transplantation, or penetrating keratoplasty were given. PTK is a valuable therapeutic alternative for superficial infectious keratitis. It can effectively eradicate lesions, hasten reepithelialization, and restore and preserve useful visual function. However, the selection of surgery candidates should be conducted carefully.

  9. [193 excimer laser trepanation in perforating keratoplasty. Report of 70 patients].

    Science.gov (United States)

    Naumann, G O; Seitz, B; Lang, G K; Langenbucher, A; Kus, M M

    1993-10-01

    In penetrating keratoplasty, trephination with the 193 nm excimer laser may help avoid the differences in the deformation of the donor and recipient wound margins which occur with the conventional procedure. By varying the shape of the "open metal mask", other cut configurations can be achieved besides circular. Thus, "vertical tilt" and "horizontal torsion", both potential reasons for persistent long-term astigmatism after PK, may be minimized. Following experimental studies, the authors present the results obtained in their first 70 consecutive patients. 38 women and 32 men were treated (mean age 60.6 years, range 17 to 89 years). Indications were corneal processes without vascularization: Fuchs' dystrophy (n = 32), other stromal dystrophies (n = 5), secondary corneal endothelial decompensation (n = 6), keratoconus (n = 15), nonvascularized corneal scars (n = 4) and miscellaneous (n = 8 ). We used elliptical metal masks with/without orientation teeth and circular masks with four and eight orientation teeth, respectively. The HeNe aiming beam was manually controlled by a micromanipulator ("joystick"). The technical data of the laser were as follows: spot mode, 1.5 x 1.5 mm; repetition rate 30/sec and 25/sec, respectively; pulse energy 15-25 mJ; mean number of pulses 6407 (recipient) and 9150 (donor). With an elliptical outline, wound closure was usually achieved with single sutures. With a circular outline with orientation teeth, wound closure was most commonly achieved with a double running suture. Patients were prospectively documented using modified Erlangen record sheets. Follow-up ranged from 3 months to 3.4 years (mean 11.4 months). With two exceptions, penetration of the anterior chamber with the 193 nm excimer laser was accomplished without deformation of the cut edges. The elliptical outline facilitated fitting of the graft into the recipient wound bed, and the orientation teeth made fitting even easier. Initial intraoperative complications due to

  10. Comparison of 3D surfaces produced by 248-nm and 193-nm excimer laser radiation

    Science.gov (United States)

    Toenshoff, Hans K.; Graumann, Christoph; Rinke, Marcus; Hesener, Hanno; Kulik, Christian

    1998-10-01

    Currently there is a strong demand for refractive optical elements made from glass in 21/2D and 3D-structures. Due to the characteristics of brittle materials like glass, only a limited number of manufacturing methods can be used to machine these materials with sub-micron resolution. Thus, current microstructures made out of glass are mainly manufactured by photolithography and etching process. Lithography techniques are only for economic purposes for a series production, but is not suitable for manufacturing prototypes or a small series. Micromachining done with Excimer Lasers in combination with high precision CNC- controlled handling systems offers flexible design possibilities for optical components. Due to the limitations of conventional machining techniques for brittle materials, a new laser machining system for material processing at a wavelength of 193 nm has been designed and built. The better absorption of 193 nm compared to 248 nm or larger wavelengths leads to damage free microstructuring of most glasses. Data generation for the volume to be ablated starts with the mathematical description of the surface shape of the optical component. The contour can be derived from a mathematical function or individual xyz-data point information from any CAD-program. A pre-processor calculates the CNC-data for laser triggering, xyz-table and the CNC- mask control. Each laser pulse leads to a material removal, defined by the illuminated surface on the workpiece as well as the energy density. Superposition or overlapping of pulses allows the creation of the desired surface. The surface roughness is determined by the wavelength as well as the chosen ablation strategy. To achieve best results, the process has to be carefully adjusted for a specific material. This technique is a sufficient method for structuring grooves in ceramics or glass as well as producing aspherical transparent optical surfaces or micro lens arrays. This paper shall describe the potential of 193 nm

  11. Effect of time sequences in scanning algorithms on the surface temperature during corneal laser surgery with high-repetition-rate excimer laser.

    Science.gov (United States)

    Mrochen, Michael; Schelling, Urs; Wuellner, Christian; Donitzky, Christof

    2009-04-01

    To investigate the influence of temporal and spatial spot sequences on the ocular surface temperature increase during corneal laser surgery with a high-repetition-rate excimer laser. Institute for Refractive and Ophthalmic Surgery, Zurich, Switzerland, and WaveLight AG, Erlangen, Germany. An argon-fluoride excimer laser system working at a repetition rate of 1050 Hz was used to photoablate bovine corneas with various myopic, hyperopic, and phototherapeutic ablation profiles. The temporal distribution of ablation profiles was modified by 4 spot sequences: line, circumferential, random, and an optimized scan algorithm. The increase in ocular surface temperature was measured using an infrared camera. The maximum and mean ocular surface temperature increases depended primarily on the spatial and temporal distribution of the spots during photoablation and the amount of refractive correction. The highest temperature increases were with the line and circumferential scan sequences. Significant lower temperature increases were found with the optimized and random scan algorithms. High-repetition-rate excimer laser systems require spot sequences with optimized temporal and spatial spot distribution to minimize the increase in ocular surface temperature. An ocular surface temperature increase will always occur depending on the amount of refractive correction, the type of ablation profile, the radiant exposure, and the repetition rate of the laser system.

  12. Excimer laser-assisted recanalisation of femoral arterial stenosis or occlusion caused by the use of Angio-Seal

    Energy Technology Data Exchange (ETDEWEB)

    Steinkamp, H.J.; Werk, M.; Beck, A.; Teichgraeber, U.; Haufe, M.; Felix, R. [Dept. of Radiology, Humboldt Univ. Berlin (Germany)

    2001-08-01

    The aim of this study was to demonstrate the effect of excimer laser and balloon angioplasty of femoral artery stenosis and occlusion after use of a haemostatic puncture closure device. A haemostatic puncture closure device (Angio-Seal) was used in 6000 patients after diagnostic or therapeutic artery catheterisation. In 34 of those patients symptoms of peripheral artery disease occurred. Sixteen of those 34 cases were transferred to our clinic for excimer laser angioplasty. All 16 patients presented with symptoms of acute peripheral artery disease within 1-14 days: superficial femoral artery (SFA) occlusions (4 cases); superficial femoral artery stenosis (3 cases); high-grade stenosis of the common femoral artery (CFA; 3 cases); high-grade stenosis of CFA; SFA and profund femoral artery (PFA; 3 cases); and occlusions of CFA, SFA and PFA (3 cases). Before any procedure was performed, informed consent was given by the patient, which included the use of the Angio-Seal closure device. Every patient who had to undergo recanalisation procedures gave additional informed consent which especially included the usage of the excimer laser for recanalisation. A measurement of the walking distance, ankle-brachial systolic pressure index (ABI) and diagnostic angiography was performed in 13 cases before and immediate after as well as 3 and 6 months after therapeutic percutaneous transluminal laser angioplasty followed by balloon angioplasty (PTLA/PTA). In 3 patients the risks of PTLA/PTA was considered too high; those patients underwent surgical repair. Angiographic and clinical improvement was achieved in 13 of 13 patients. The mean walking distance increased from 81 to >400 m. The average ankle-brachial systolic pressure index (ABI) increased from 0.47 to 0.84. One patient developed a dissection of the SFA, and in 1 case a peripheral embolisation was seen. The PTLA/PTA technique is a successful therapeutic option for patients with femoral artery occlusion or high-grade stenosis

  13. Effects of excimer laser annealing on low-temperature solution based indium-zinc-oxide thin film transistor fabrication

    Directory of Open Access Journals (Sweden)

    Chao-Nan Chen

    2015-04-01

    Full Text Available A Solution Based Indium-Zinc-Oxide thin-film transistor (TFT with a field-effect mobility of 0.58 cm2/Vs, a threshold voltage of 2.84 V by using pulse laser annealing processes. Indium-zinc-oxide (IZO films with a low process temperature were deposited by sol-gel solution based method and KrF excimer laser annealing (wavelength of 248 nm. Solution based indium-zinc-oxide (IZO films usually needs high temperature about 500 °C post annealing in a oven. KrF excimer laser annealing shows advantages of low temperature process, the less process time deceases to only few seconds was used to replace the high temperature process. IZO thin films suffering laser irradiation still keeps the amorphous film quality by transmission electron microscopy (TEM diffraction pattern analysis. It could be expected this technology to large-area flexible display, in the future.

  14. A comparative study of via drilling and scribing on PEN and PET substrates for flexible electronic applications using excimer and Nd:YAG laser sources

    NARCIS (Netherlands)

    Mandamparambil, R.; Fledderus, H.; Brand, J. van den; Saalmink, M.; Kusters, R.; Podprocky, T.; Steenberge, G. van; Baets, J. de; Dietzel, A.H.

    2009-01-01

    A study on via drilling and channel scribing on PEN and PET substrates for flexible electronic application is discussed in this paper. For the experiments, both KIF excimer laser (248 nm) and frequency tripled Nd:YAG (355 nm) laser are used. Different measurement techniques like optical microscopy,

  15. Early changes in ocular surface and tear inflammatory mediators after small-incision lenticule extraction and femtosecond laser-assisted laser in situ keratomileusis.

    Directory of Open Access Journals (Sweden)

    Shaohui Gao

    Full Text Available To characterize the early ocular-surface changes or tear inflammatory-mediators levels following small-incision lenticule extraction (ReLEx smile and femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK.Forty-seven myopic subjects were recruited for this prospective study. Fifteen underwent ReLEx smile and thirty-two underwent FS-LASIK. Corneal fluorescein (FL staining, tear break-up time (TBUT, Schirmer I test (SIT, ocular surface disease index (OSDI and central corneal sensitivity were evaluated in all participants. Tears were collected and analyzed for interleukin-6 (IL-6, tumor necrosis factor-α (TNF-α, nerve growth factor (NGF and intercellular adhesion molecule-1 (ICAM-1 levels using multiplex magnetic beads. All measurements were preformed preoperatively and 1 day, 1 week, 1 month and 3 months postoperatively.FL scores in ReLEx smile group were lower than those of FS-LASIK group 1 week postoperatively (P = 0.010. Compared to the FS-LASIK group, longer TBUT were observed in ReLEx smile group 1 month (P = 0.029 and 3 months (P = 0.045 postoperatively. No significant differences were found in tear secretion for the two groups (P>0.05. OSDI scores were higher in FS-LASIK group 1 month after surgery (P = 0.020. Higher central corneal sensitivity was observed in ReLEx smile group 1 week, 1 month and 3 months (P0.05. Moreover, IL-6 and NGF levels correlated with ocular surface changes after ReLEx smile or FS-LASIK.In the early postoperative period, ReLEx smile results in milder ocular surface changes than FS-LASIK. Furthermore, the tear inflammatory mediators IL-6 and NGF may play a crucial role in the ocular surface healing process following ReLEx smile and FS-LASIK.

  16. Corneal haze induced by excimer laser photoablation in rabbits is reduced by preserved human amniotic membrane graft

    Science.gov (United States)

    Wang, Ming X.; Gray, Trevor; Prabhasawat, Pinnita; Ma, Xiong; Culbertson, William; Forster, Richard; Hanna, Khalil; Tseng, Scheffer C. G.

    1998-06-01

    We conducted a study to determine if preserved human amniotic membrane can reduce corneal haze induced by excimer laser photoablation. Excimer photoablation was performed bilaterally on 40 New Zealand white rabbits with a 6 mm ablation zone and 120 micrometer depth (PTK) using the VISX Star. One eye was randomly covered with a preserved human amniotic membrane and secured using four interrupted 10 - 0 nylon sutures; the other eye served as control. The amniotic membranes were removed at one week, and the corneal haze was graded with a slit-lamp biomicroscopy by three masked corneal specialists (WC, KH and RF) biweekly for the ensuing 12 weeks. Histology and in situ TUNEL staining (for fragmented DNA as an index for apoptosis) was performed at days 1, 3 and 7 and at 12 weeks. One week after excimer photoablation, the amniotic membrane-covered corneas showed more anterior stromal edema, which resolved at the second week. A consistent grading of organized reticular corneal haze was noted among the three masked observers. Such corneal haze peaked at the seventh week in both groups. The amniotic membrane-covered group showed statistically significant less corneal haze (0.50 plus or minus 0.15) than the control groups (1.25 plus or minus 0.35) (p less than 0.001). The amniotic membrane-covered corneas had less inflammatory response at days 1 and 3, showing nearly nil DNA fragmentation on keratocytes on the ablated anterior stromal and less stromal fibroblast activation. There is less altered epithelial cell morphology and less epithelial hyperplasia at 1 week in these amniotic membrane-treated eyes. We concluded from this study that amniotic membrane matrix is effective in reducing corneal haze induced by excimer photoablation in rabbits and may have clinical applications.

  17. Pigmentation above the constitutive level: an indicator of excimer laser radiation-induced erythema in Koreans.

    Science.gov (United States)

    Choi, Jee-Woong; Na, Se-Young; Chung, Mi-Young; Na, Jung-Im; Huh, Chang-Hun; Youn, Sang-Woong; Kang, Hee-Young; Park, Kyoung-Chan

    2012-07-01

    Ultraviolet (UV) irradiation induces skin erythema, but it is not clear which factors have the greatest effects on UV sensitivity. Six healthy Korean adult men were enrolled and their melanin index (MI) and increment of erythema index (ΔEI) were measured. In each individual, 12 different sites were selected and 36 spots were irradiated with a single shot of monochromatic excimer laser with a dose of 350 mJ/cm(2) . The sites were categorized into three groups based on the cumulative sun exposure: UZ, unexposed zones; FEZ, frequently exposed zones; and IEZ, intermittently exposed zones. The sun exposure indexes (SEI) were also calculated based on previously described methods. ΔEI, MI and SEI were measured and calculated. The ΔEI of UZ was significantly higher than that of FEZ, but lower than that of IEZ. In general, there was a significant relationship between ΔEI and MI (R(2) = 0.135). However, IEZ did not show significant results. In contrast, there was a stronger relationship between ΔEI and SEI (R(2) = 0.344). Overall, the values were significantly higher for the SEI (0.541 [UZ], 0.281 [IEZ] and 0.228 [FEZ]) than for MI (0.311 [UZ], 0.011 [IEZ] and 0.073 [FEZ]). There were significant site variations in UV sensitivity along with skin pigmentation. In addition, significant differences were observed according to the exposure frequency. The SEI was found to be strongly correlated with UV sensitivity. These results suggest that the induced level of pigmentation above the constitutive level will be a better indicator for UV sensitivity than baseline MI. © 2012 Japanese Dermatological Association.

  18. Excimer laser micropatterning of freestanding thermo-responsive hydrogel layers for cells-on-chip applications

    Science.gov (United States)

    Santaniello, Tommaso; Martello, Federico; Tocchio, Alessandro; Gassa, Federico; Webb, Patrick; Milani, Paolo; Lenardi, Cristina

    2012-10-01

    We report a novel reliable and repeatable technologic manufacturing protocol for the realization of micro-patterned freestanding hydrogel layers based on thermo-responsive poly-(N-isopropyl)acrylamide (PNIPAAm), which have potential to be employed as temperature-triggered smart surfaces for cells-on-chip applications. PNIPAAm-based films with controlled mechanical properties and different thicknesses (100-300 µm thickness) were prepared by injection compression moulding at room temperature. A 9 × 9 array of 20 µm diameter through-holes is machined by means of the KrF excimer laser on dry PNIPAAm films which are physically attached to flat polyvinyl chloride (PVC) substrates. Machining parameters, such as fluence and number of shots, are optimized in order to achieve highly resolved features. Micro-structured freestanding films are then easily obtained after hydrogels are detached from PVC by gradually promoting the film swelling in ethanol. In the PNIPAAm water-swollen state, the machined holes’ diameter approaches a slight larger value (30 µm) according to the measured hydrogel swelling ratio. Thermo-responsive behaviour and through-hole tapering characterization are carried out by metrology measurements using an optical inverted and confocal microscope setup, respectively. After the temperature of freestanding films is raised above 32 °C, we observe that the shrinkage of the whole through-hole array occurs, thus reducing the holes’ diameter to less than a half its original size (about 15 µm) as a consequence of the film dehydration. Different holes’ diameters (10 and 30 µm) are also obtained on dry hydrogel employing suitable projection masks, showing similar shrinking behaviour when hydrated and undergone thermo-response tests. Thermo-responsive PNIPAAm-based freestanding layers could then be integrated with other suitable micro-fabricated thermoplastic components in order to preliminary test their feasibility in operating as temperature

  19. Uncorrected and Corrected Distance Visual Acuity, Predictability, Efficacy, and Safety after Femtosecond Laser in Situ Keratomileusis (FS-LASIK) and Refractive Lenticule extraction (ReLEx) for Moderate and High Myopia

    DEFF Research Database (Denmark)

    Vestergaard, Anders; Justesen, Birgitte Larsen; Melsen, Charlotte

    Title: Uncorrected and Corrected Distance Visual Acuity, Predictability, Efficacy, and Safety after Femtosecond Laser in Situ Keratomileusis (FS-LASIK) and Refractive Lenticule extraction (ReLEx) for Moderate and High Myopia. Vestergaard A., Justesen B., Melsen C., Lyhne N., Department of Ophthal......Title: Uncorrected and Corrected Distance Visual Acuity, Predictability, Efficacy, and Safety after Femtosecond Laser in Situ Keratomileusis (FS-LASIK) and Refractive Lenticule extraction (ReLEx) for Moderate and High Myopia. Vestergaard A., Justesen B., Melsen C., Lyhne N., Department...... months after surgery. Conclusions: Both FS-LASIK and ReLEx are efficient in treating myopia and myopic astigmatism. ReLEx is a promising new all-in-one femtosecond laser refractive procedure with results, concerning predictability and efficacy, that seemed comparable to or better than FS-LASIK after 3...

  20. Influence of laser beam’s image-plane position on geometry of through-holes in percussion-drilled glass using excimer laser

    Directory of Open Access Journals (Sweden)

    Ales Babnik

    2013-01-01

    Full Text Available We study the influence of a laser beam’s image-plane position relative to the processed surface for the deep-hole, laser-microdrilling of soda-lime glass with an excimer 308-nm laser and mask-projection technique. It is demonstrated that the image-plane position has a significant influence on the hole’s tapering and final depth. Holes with exit diameters up to 10 times smaller than the mask-image diameter are produced in the case of perforation during the appropriate process phase determined by the formation of the plasma plume.

  1. Wettability characteristics of a modified mild steel with CO2, Nd:YAG, excimer and high power diode lasers

    OpenAIRE

    Lawrence, Jonathan; Li, Lin

    1999-01-01

    Interaction of CO2, Nd:YAG, excimer and high-power diode laser radiation with the surface of a common mild steel (EN8) was found to effect changes in the wettability characteristics of the steel, namely changes in the measured contact angle of certain liquids. Such changes were identified as being due to modifications to (i) the surface roughness, (ii) changes in the surface oxygen content and (iii) changes in the surface energy of the mild steel. However, it was found that changes in the wet...

  2. Controllable Change of Photoluminescence Spectra of Silicone Rubber Modified by 193 nm ArF Excimer Laser

    Science.gov (United States)

    Okoshi, Masayuki; Iyono, Minako; Inoue, Narumi

    2009-12-01

    Photoluminescence spectra of silicone rubber ([SiO(CH3)2]n) photochemically modified by a 193 nm ArF excimer laser was found to be controllable. Compared with the modification in air, the photoluminescence spectra could be blueshifted by the modification in vacuum or the additional irradiation of ArF excimer laser in vacuum after the modification in air. To redshift, on the other hand, the additional irradiation of a 157 nm F2 laser in air after the modification in air, the modification in oxygen gas, or the postannealing after the modification in oxygen gas was effective. The blue and redshifts of the photoluminescence were essentially due to the acceleration of reduction and oxidation reactions of silicone rubber, respectively, because the photoluminescence derives its origin from oxygen deficiency centers and peroxy centers of the silica structure in the modified silicone rubber. On the basis of the spectra changes, colorful light-guiding sheets made of silicone rubber under illumination of a 375 nm light-emitting diode were successfully fabricated for cellular phone use.

  3. Corneal lathing using the excimer laser and a computer-controlled positioning system: Part I--Lathing of epikeratoplasty lenticules.

    Science.gov (United States)

    Altmann, J; Grabner, G; Husinsky, W; Mitterer, S; Baumgartner, I; Skorpik, F; Asenbauer, T

    1991-01-01

    Precise lathing of epikeratoplasty lenticules is difficult to achieve with the cryolathe due to unpredictable expansion of the lathing tools and the corneal tissue during the freezing process. In addition, the procedure destroys all viable cells in the transplant thereby possibly contributing to the prolonged period of visual rehabilitation. Non-freezing techniques using the microkeratome or the rotor-trephine, on the other hand, are technically demanding, can cause mechanical damage during cutting or fixation, and, have not given consistently reproducible refractive results. A new system is presented that allows a variable laser ablation of donor corneas into lenticules for aphakic and myopic epikeratoplasty, as well as for lamellar keratoplasty. With the help of a computer-controlled positioning system that uses high-precision micropositioning elements (both translation and rotational stages) the donor cornea is moved, epithelial side down, in a holding device in front of a focused excimer laser beam (ArF, lambda = 193 nm). This photoablation lathing process assures the viability of the stromal cells in the lenticule in close approximation to the treated surface. The user friendly computer software allows the fast and convenient selection of a variety of parameters, such as the diameter of the optical zone, the shape of the wing zone, the refractive power, the central thickness of the lenticule and the overall contour of the transplant. The first laboratory data of lenticules prepared from human corneas with this "Excimer Laser Corneal Shaping System" are presented.

  4. Corneal lathing using the excimer laser and a computer-controlled positioning system: Part II--Variable trephination of corneal buttons.

    Science.gov (United States)

    Husinsky, W; Mitterer, S; Altmann, J; Grabner, G; Baumgartner, I; Skorpik, F; Asenbauer, T

    1991-01-01

    A new system is presented that allows a variable trephination of donor corneas for the preparation of corneal buttons used in penetrating keratoplasty. With the help of a computer-controlled positioning system that uses high-precision micropositioning elements (both translation and rotational stages) the donor cornea is removed, epithelial side up, in a fixation device in front of a focused excimer laser beam (ArF, lambda = 193 nm). User friendly computer software allows the surgeon to select a variety of parameters (diameter, shape, angle of trephination) of the corneal graft. Histological and electron microscopical data of human corneas trephined with this "Excimer Laser Corneal Shaping System" are presented.

  5. Update on excimer laser photorefractive keratectomy (PRK) at Cedars-Sinai Medical Center: two-year experience

    Science.gov (United States)

    Maguen, Ezra I.; Salz, James J.; Warren, Cathy; Papaioannou, Thanassis; Nesburn, Anthony B.; Macy, Jonathan I.; Hofbauer, John; Grundfest, Warren S.

    1993-06-01

    Our two year experience with excimer laser photorefractive keratectomy for the correction of myopia on 160 eyes of 128 patients is described. All eyes were treated with a VISX Twenty- Twenty excimer laser, with the following parameters: radiant exposure 160 mJ/cm2, frequency 5 Hz, ablation zone diameter 5.0 to 5.5 mm, and stromal ablation rate 0.18 to 0.33 (mu) /pulse. A suction fixation ring was used in all cases either with nitrogen flow (79 eyes) or without nitrogen flow (81 eyes) across the cornea. Follow-up ranged from one month (152 eyes) to 24 months (12 eyes). The results are stable between 3 and 24 months with less than 0.25 D change in the mean postoperative spherical equivalents. In eyes with a follow-up of 6 to 24 months, 77% to 100% were 20/40 or better uncorrected, and 84% to 92% were corrected to within +/- 1 D of emmetropia. Further follow-up is needed to assess the long term safety and efficacy of the procedure.

  6. Formation of periodic microswelling structures on silicone rubber surface using ArF excimer laser to realize superhydrophobic property

    Science.gov (United States)

    Nojiri, Hidetoshi; Setyo Pambudi, Wisnu; Okoshi, Masayuki

    2017-07-01

    Periodic microswelling structures were photochemically induced on a silicone rubber surface using a 193 nm ArF excimer laser. Microspheres made of silica glass (SiO2) of 2.5 µm diameter were aligned on the silicone rubber surface during laser irradiation; the laser beam was focused on the silicone surface underneath each microsphere. The height and diameter of the formed microswelling structures were found to be controllable by changing the Ar gas flow rate, single-pulse laser fluence, and laser irradiation time. The chemical bonding of the laser-irradiated sample did not change and thus remained to be a silicone, as analyzed by X-ray photoelectron spectroscopy. As a result, microswelling structures of approximately 1.3 µm height and 1.3 µm diameter were successfully obtained. The contact angles of water on the microstructured silicone were measured to be 150° and larger, clearly indicating superhydrophobicity. The mechanism by which the microswellings form their shape was discussed on the basis of the changes in the focal point and spot size during laser irradiation through the SiO2 microsphere.

  7. Early changes in ocular surface and tear inflammatory mediators after small-incision lenticule extraction and femtosecond laser-assisted laser in situ keratomileusis.

    Science.gov (United States)

    Gao, Shaohui; Li, Saiqun; Liu, Liangping; Wang, Yong; Ding, Hui; Li, Lili; Zhong, Xingwu

    2014-01-01

    To characterize the early ocular-surface changes or tear inflammatory-mediators levels following small-incision lenticule extraction (ReLEx smile) and femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK). Forty-seven myopic subjects were recruited for this prospective study. Fifteen underwent ReLEx smile and thirty-two underwent FS-LASIK. Corneal fluorescein (FL) staining, tear break-up time (TBUT), Schirmer I test (SIT), ocular surface disease index (OSDI) and central corneal sensitivity were evaluated in all participants. Tears were collected and analyzed for interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), nerve growth factor (NGF) and intercellular adhesion molecule-1 (ICAM-1) levels using multiplex magnetic beads. All measurements were preformed preoperatively and 1 day, 1 week, 1 month and 3 months postoperatively. FL scores in ReLEx smile group were lower than those of FS-LASIK group 1 week postoperatively (P = 0.010). Compared to the FS-LASIK group, longer TBUT were observed in ReLEx smile group 1 month (P = 0.029) and 3 months (P = 0.045) postoperatively. No significant differences were found in tear secretion for the two groups (P>0.05). OSDI scores were higher in FS-LASIK group 1 month after surgery (P = 0.020). Higher central corneal sensitivity was observed in ReLEx smile group 1 week, 1 month and 3 months (Ptears was observed in ReLEx smile group postoperatively (PTears TNF-α and ICAM-1 concentrations were not significantly different between the two groups at any follow-up time (P>0.05). Moreover, IL-6 and NGF levels correlated with ocular surface changes after ReLEx smile or FS-LASIK. In the early postoperative period, ReLEx smile results in milder ocular surface changes than FS-LASIK. Furthermore, the tear inflammatory mediators IL-6 and NGF may play a crucial role in the ocular surface healing process following ReLEx smile and FS-LASIK.

  8. [Comparison of the effects of different side-cut angles on corneal biomechanical properties after femtosecond laser assisted-laser in situ keratomileusis].

    Science.gov (United States)

    Li, H; Wang, Y; Dou, R; Wang, L; Xu, L L; Li, X J; Zhang, J M

    2017-01-11

    Objective: To evaluate the effects of side-cut angles on corneal biomechanical properties after femtosecond laser assisted-laser in situ keratomileusis (FS-LASIK). Methods: In this clinical control study, 97 right eyes of 97 patients with myopia and myopic astigmatism undergoing FS-LASIK surgery were included randomly. Two types of side-cut angles were designed for the flap, 90° in 48 eyes and 130° in 49 eyes. The values of corneal resistance factor (CRF), cornea hysteresis (CH) and 37 biomechanical waveform parameters were measured using the ocular response analyzer preoperatively and at 1 and 3 months postoperatively. The comparison between the two groups at different follow-up time points was made with one-way analysis of variance, and the comparison among different follow-up time points in each group was performed with the repeated measures analysis of variance. Results: The mean CRF, CH, p area, h, dive1, dive2, w11 and w21 in both groups showed significant reduction at 1 month postoperatively (group 90°: CRF 10.49 vs. 6.85, CH 10.02 vs. 7.55, p1 area 3 537.54 vs. 1 918.07, h1 404.74 vs. 283.25, dive1 350.63 vs. 243.33, w11 10.50 vs. 7.58. group 130°: CRF 10.14 vs. 6.38, CH 9.93 vs. 7.13, p1 area 3 498.93 vs. 2 038.74, h1 411.93 vs. 304.49, dive1 352.51 vs. 265.12, w11 10.55 vs. 7.78. PCorneal biomechanical properties significantly decrease after FS-LASIK, and different side-cut angles have some effect on corneal biomechanical properties after FS-LASIK. The corneal deformation is more stable after flap creation with an obtuse side-cut angle making the cornea under stress. Combined with waveform parameters of the ocular response analyzer, more subtle changes of corneal biomechanical properties can be found. (Chin J Ophthalmol, 2017, 53:23-32).

  9. Determination of the melting threshold of TiO{sub 2} thin films processed by excimer laser irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Van Overschelde, O. [Chimie des Interactions Plasma-Surface, Universite de Mons, 23, Place du Parc, 7000 Mons (Belgium); Delsate, T. [Service de Physique Theorique et Mathematique, Universite de Mons, 6 Avenue du champ de Mars, 7000 Mons (Belgium); Snyders, R. [Chimie des Interactions Plasma-Surface, Universite de Mons, 23, Place du Parc, 7000 Mons (Belgium); Materia Nova Research Center, 1 Avenue Copernic, 7000 Mons (Belgium)

    2012-06-15

    Processing surfaces by laser needs an understanding of the mechanisms generated by irradiation. In this work, to gain understanding of the mechanisms occurring during irradiation of TiO{sub 2} thin films by means of KrF excimer laser, we have performed infrared time resolved reflectivity measurements. This experimental investigation revealed modifications of the heating/cooling cycle as a function of the fluence (F). These modifications start appearing for a fluence value of about {approx}0.25 J/cm{sup 2} which is associated with the melting threshold of the film. Additionally, we have solved numerically the heat equation of the system with specific boundary conditions. From these calculations, we have established the thermal history of the film during the 25 ns irradiation pulse. The data reveal that a part of the medium liquefies around a fluence of 0.23 J/cm{sup 2} in good agreement with the experimental data.

  10. Improving the ablation efficiency of excimer laser systems with higher repetition rates through enhanced debris removal and optimized spot pattern.

    Science.gov (United States)

    Arba-Mosquera, Samuel; Klinner, Thomas

    2014-03-01

    To evaluate the reasons for the required increased radiant exposure for higher-repetition-rate excimer lasers and determine experimentally possible compensations to achieve equivalent ablation profiles maintaining the same single-pulse energies and radiant exposures for laser repetition rates ranging from 430 to 1000 Hz. Schwind eye-tech-solutions GmbH and Co. KG, Kleinostheim, Germany. Experimental study. Poly(methyl methacrylate) (PMMA) plates were photoablated. The pulse laser energy was maintained during all experiments; the effects of the flow of the debris removal, the shot pattern for the correction, and precooling the PMMA plates were evaluated in terms of achieved ablation versus repetition rate. The mean ablation performance ranged from 88% to 100%; the variability between the profile measurements ranged from 1.4% to 6.2%. Increasing the laser repetition rate from 430 Hz to 1000 Hz reduced the mean ablation performance from 98% to 91% and worsened the variability from 1.9% to 4.3%. Increasing the flow of the debris removal, precooling the PMMA plates to -18°C, and adapting the shot pattern for the thermal response of PMMA to excimer ablation helped stabilize the variability. Only adapting the shot pattern for the thermal response of PMMA to excimer ablation helped stabilize the mean ablation performance. The ablation performance of higher-repetition-rate excimer lasers on PMMA improved with improvements in the debris removal systems and shot pattern. More powerful debris removal systems and smart shot patterns in terms of thermal response improved the performance of these excimer lasers. Copyright © 2014 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  11. Species-resolved laser-probing investigations of the hydrodynamics of KrF excimer and copper vapor laser ablation processing of materials

    Science.gov (United States)

    Ventzek, Peter L. G.; Gilgenbach, Ronald M.; Ching, Chi H.; Lindley, R. A.

    1993-06-01

    Hydrodynamic phenomena from KrF excimer laser ablation (10-3-20 J/cm2) of polyimide, polyethyleneterephthalate, and aluminum are diagnosed by laser beam deflection, schlieren photography, shadowgraphy, laser-induced-fluorescence and dye-laser- resonance absorption photography (DLRAP). Experiments were performed in vacuum and gaseous environments (10-5 to 760 Torr). In vacuum, the DLRAP diagnostic shows species-resolved plume expansion which is consistent with that of a reflected rarefaction wave. Increasing the background gas pressure reveals the formation of sound/shock compared to CN in the laser-ablated polyimide (Vespel) plume/shock in inert (e.g. argon) and reactive (e.g. air) gases. At low pressures (less than 10 Torr) Al and CN species are in close contact with the shock front. As the pressure increases, the species front tends to recede, until at high pressures (over 200 Torr) the species are restrained to only a few mm above the target surface. After sufficient expansion, Al and CN are no longer detectable; only the shadowgraph of the hot gas plume remains. Since CN is observable in both inert and reactive environments, it can be concluded that CN is not a reaction product between the background gas and the ablated species. By way of comparison to excimer laser ablation processing of materials, copper vapor laser machined polyimide and polymethylmethacrylate (transparent to green and yellow copper vapor laser light) are also investigated. The two polymers are observed to have markedly different machined surfaces. Hydrodynamic effects for the copper vapor laser machined materials are investigated using HeNe laser beam deflection.

  12. Excimer laser phototherapeutic keratectomy : Indications, results and its role in the Indian scenario

    Directory of Open Access Journals (Sweden)

    Rao Srinivas

    1999-01-01

    Full Text Available PURPOSE: To report indications, technique, and results of excimer phototherapeutic keratectomy (PTK, and describe possible reasons for the small numbers of such procedures performed in a referral institute in India. METHODS: Retrospective review of case records of 10 patients (11 eyes who underwent excimer PTK at our institute between February 1994 and September 1997. RESULTS: Corneal scars were the most common indication for treatment. Best-corrected visual acuity (BCVA improved in 6 eyes (mean: 2 lines of Snellen acuity. All eyes had BCVA > or = 6/12 after treatment. None of the patients experienced loss of BCVA after treatment. Unaided visual acuity improved in 3 eyes and decreased in 2 eyes. Change in spherical equivalent refraction > or = 1 diopter occurred in 77.8% of eyes after treatment. Treating central corneal scars resulted in a significant hyperopic shift in refraction. CONCLUSIONS: Excimer PTK is a safe and effective procedure for the treatment of superficial corneal opacities. Post-treatment ametropia may require further correction with optical aids. Inappropriate referrals, deep corneal scars, and cost of the procedure could have contributed to the small numbers of PTK performed at our institute. Improved understanding of procedural strengths and limitations could lead to increased use of this procedure, with satisfying results in selected patients.

  13. Effects of 308 nanometer excimer laser energy on 316 L stainless-steel stents: implications for laser atherectomy of in-stent restenosis.

    Science.gov (United States)

    Burris, N; Lippincott, R A; Elfe, A; Tcheng, J E; O'Shea, J C; Reiser, C

    2000-11-01

    To determine the effects of the incidental exposure of stents to pulsed 308 nanometer ultraviolet excimer laser energy. Five types of 316 L stainless-steel coronary stents were subjected to two types of study. First, for endurance testing, sixty stents were deployed in 3.0Eth 4.0 mm polymer tubes in three geometries. Up to 1,000 laser pulses were delivered while advancing a 2.0 mm eccentric catheter through the lumen of the stent. These stents were next subjected to 400 million simulated heartbeats and then analyzed for metal etching and fatigue. Second, six additional stents were irradiated with 1,000 pulses underwater and then analyzed for particulates, anions and cations liberated from the stent. Photomicroscopy revealed surface etching on a number of stents. Two stent models exhibited multiple strut fractures at the strut joints in both test samples and controls. In no case was a break observed at the site of laser-stent interaction. Breakage frequency was not significantly different between lazed stents and controls. Lazed stents produced a mean of 14 micrograms of sodium and 4 micrograms of iron more than controls. No excess particulates were detected. Under model conditions typical of clinical use, excimer laser treatment does not alter stainless-steel stent endurance or liberate clinically significant material from the stent.

  14. AFM study of excimer laser patterning of block-copolymer: Creation of ordered hierarchical, hybrid, or recessed structures

    Energy Technology Data Exchange (ETDEWEB)

    Švanda, Jan; Siegel, Jakub; Švorčík, Vaclav; Lyutakov, Oleksiy, E-mail: lyutakoo@vscht.cz

    2016-05-15

    Highlights: • Combination of bottom-up (BCP separation) and top-down (laser patterning) technologies allows obtaining hierarchical structures. • Surface morphologies were determined by the order of patterning steps (laser modification, annealing, surface reconstruction). • Tuning the order of steps enables the reorientation of BCP domain at large scale, fabrication of hierarchical, hybrid or recessed structures. • The obtained structures can find potential applications in nanotechnology, plasmonics, information storage, sensors and smart surfaces. - Abstract: We report fabrication of the varied range of hierarchical structures by combining bottom-up self-assembly of block copolymer poly(styrene-block-vinylpyridine) (PS-b-P4VP) with top-down excimer laser patterning method. Different procedures were tested, where laser treatment was applied before phase separation and after phase separation or phase separation and surface reconstruction. Laser treatment was performed using either polarized laser light with the aim to create periodical pattern on polymer surface or non-polarized light for preferential removing of polystyrene (PS) part from PS-b-P4VP. Additionally, dye was introduced into one part of block copolymer (P4VP) with the aim to modify its response to laser light. Resulting structures were analyzed by XPS, UV–vis and AFM techniques. Application of polarized laser light leads to creation of structures with hierarchical, recessed or hybrid geometries. Non-polarized laser beam allows pronouncing the block copolymer phase separated structure. Tuning the order of steps or individual step conditions enables the efficient reorientation of block-copolymer domain at large scale, fabrication of hierarchical, hybrid or recessed structures. The obtained structures can find potential applications in nanotechnology, photonics, plasmonics, information storage, optical devices, sensors and smart surfaces.

  15. Electronic and crystalline structure of Si/SiO 2 interface modified by ArF excimer laser

    Science.gov (United States)

    Cháb, V.; Lukeš, I.; Ondřejček, M.; Jiříček, P.

    The native oxide layers on Si(100) surface were irradiated under UHV conditions by an ArF excimer laser pulses with energy density varied between melting and evaporating thresholds. The resulting changes were studied by LEED, AES and UPS. The increase of the energy density up to evaporation threshold results in the recrystallisation of native oxide layer. The pulses with energy densities just above the evaporation threshold ablate the top layer leaving an ordered and atomicaly clean surface. The observed (1x1) surface reconstruction is probably stabilised by strains introduced during rapid melting and quenching of the topmost layers. The surface electronic structure is dominated by random satisfaction of dangling bonds swearing a well defined surface states observed on (2x1)Si(100) surface.

  16. Synthesis and properties of Ag/ZnO core/shell nanostructures prepared by excimer laser ablation in liquid

    Directory of Open Access Journals (Sweden)

    Yan Zhao

    2015-08-01

    Full Text Available Ag/ZnO core/shell nanostructure was synthesised by a 248-nm KrF excimer pulsed laser ablation in a liquid solution for the first time. It was found that the surface plasma resonance absorption of the Ag/ZnO core/shell nanostructures can be tuned by the thickness of the ZnO shell, which is in agreement with the finite difference in the time domain simulation. Furthermore, the ultraviolet emission spectrum of the Ag/ZnO core/shell nanostructures was stronger and blue-shifted compared with that of pure ZnO nanoparticles. This interesting photoluminescent phenomenon is analysed in detail and a possible explanation is proposed.

  17. The Correlation Analysis between Corneal Biomechanical Properties and the Surgically Induced Corneal High-Order Aberrations after Small Incision Lenticule Extraction and Femtosecond Laser In Situ Keratomileusis.

    Science.gov (United States)

    Wu, Wenjing; Wang, Yan

    2015-01-01

    Background. To investigate the correlation between corneal biomechanics and the surgically induced corneal high-order aberrations (HOAs) after small incision lenticule extraction (SMILE) and femtosecond laser in situ keratomileusis (FS-LASIK). Methods. A total of 150 right myopic eyes that underwent SMILE or FS-LASIK surgery were included in this retrospective study, 75 eyes in each group. The corneal hysteresis (CH) and the corneal resistance factor (CRF) with the corneal HOAs of the anterior, posterior, and total cornea were assessed preoperatively and three months postoperatively. Multivariate linear regression was applied to determine the correlations. Results. The preoperative CRF was significantly correlated with the induced 3rd-6th-order HOAs and spherical aberration of the anterior surface and the total cornea after SMILE and FS-LASIK surgeries (P cornea after SMILE surgery (P biomechanics affect the surgically induced corneal HOAs after SMILE and FS-LASIK surgery, which may be meaningful for screening the patients preoperatively and optimizing the visual qualities postoperatively.

  18. Long-Term Outcomes of Radial Keratotomy, Laser In Situ Keratomileusis, and Astigmatic Keratotomy Performed Consecutively over a Period of 21 Years

    Directory of Open Access Journals (Sweden)

    Priyanka Chhadva

    2015-01-01

    Full Text Available Purpose. To describe a case of 3 refractive procedures performed in one eye over 2 decades. Methods. Case report. Results. A 41-year-old patient presented for refractive surgery evaluation. His ocular history includes bilateral radial keratotomy performed 21 years ago for moderate myopia: spherical equivalence of −4.25 D bilaterally. Postoperative uncorrected visual acuity (UCVA was 20/30; however, over time he developed a hyperopic shift and UCVA decreased to 20/40 in the right eye. Thus, laser-assisted in situ keratomileusis (LASIK was performed at an outside institution 6.5 years later, and the patient had initial improvement of UCVA to 20/25. Due to a change in refractive error, the patient underwent uneventful astigmatic keratotomy 13 years after LASIK in the right eye, and 1.5 years after surgery best-corrected visual acuity was 20/25 with manifest refraction of −1.00+5.50×134°.  Conclusion. We report the outcomes and natural refractive progression in a patient who underwent three corneal refractive procedures over two decades. This case underlines the difficulties of long-term management of post-RK hyperopia and astigmatism.

  19. The Correlation Analysis between Corneal Biomechanical Properties and the Surgically Induced Corneal High-Order Aberrations after Small Incision Lenticule Extraction and Femtosecond Laser In Situ Keratomileusis

    Directory of Open Access Journals (Sweden)

    Wenjing Wu

    2015-01-01

    Full Text Available Background. To investigate the correlation between corneal biomechanics and the surgically induced corneal high-order aberrations (HOAs after small incision lenticule extraction (SMILE and femtosecond laser in situ keratomileusis (FS-LASIK. Methods. A total of 150 right myopic eyes that underwent SMILE or FS-LASIK surgery were included in this retrospective study, 75 eyes in each group. The corneal hysteresis (CH and the corneal resistance factor (CRF with the corneal HOAs of the anterior, posterior, and total cornea were assessed preoperatively and three months postoperatively. Multivariate linear regression was applied to determine the correlations. Results. The preoperative CRF was significantly correlated with the induced 3rd–6th-order HOAs and spherical aberration of the anterior surface and the total cornea after SMILE and FS-LASIK surgeries (P<0.05, postoperatively. The CRF was significantly correlated with the induced vertical coma of the anterior and posterior surfaces and the total cornea after SMILE surgery (P<0.05. There was a significant correlation between the CRF and the induced posterior corneal horizontal coma after FS-LASIK surgery (P=0.013. Conclusions. The corneal biomechanics affect the surgically induced corneal HOAs after SMILE and FS-LASIK surgery, which may be meaningful for screening the patients preoperatively and optimizing the visual qualities postoperatively.

  20. The Correlation Analysis between Corneal Biomechanical Properties and the Surgically Induced Corneal High-Order Aberrations after Small Incision Lenticule Extraction and Femtosecond Laser In Situ Keratomileusis

    Science.gov (United States)

    2015-01-01

    Background. To investigate the correlation between corneal biomechanics and the surgically induced corneal high-order aberrations (HOAs) after small incision lenticule extraction (SMILE) and femtosecond laser in situ keratomileusis (FS-LASIK). Methods. A total of 150 right myopic eyes that underwent SMILE or FS-LASIK surgery were included in this retrospective study, 75 eyes in each group. The corneal hysteresis (CH) and the corneal resistance factor (CRF) with the corneal HOAs of the anterior, posterior, and total cornea were assessed preoperatively and three months postoperatively. Multivariate linear regression was applied to determine the correlations. Results. The preoperative CRF was significantly correlated with the induced 3rd–6th-order HOAs and spherical aberration of the anterior surface and the total cornea after SMILE and FS-LASIK surgeries (P corneal horizontal coma after FS-LASIK surgery (P = 0.013). Conclusions. The corneal biomechanics affect the surgically induced corneal HOAs after SMILE and FS-LASIK surgery, which may be meaningful for screening the patients preoperatively and optimizing the visual qualities postoperatively. PMID:26483975

  1. Efficacy and safety of ab interno excimer laser trabeculotomy in primary open-angle glaucoma: two years of follow-up.

    Science.gov (United States)

    Babighian, Silvia; Rapizzi, Emilio; Galan, Alessandro

    2006-01-01

    Ab interno trabeculotomy was performed using the recently developed XeCl excimer laser in 21 eyes of 21 patients with primary open-angle glaucoma refractory to medical therapy. The patients were followed at the Eye Department of S. Antonio Hospital in Padova, for an average of 25.3 +/- 1.3 months. Intraocular pressure (IOP), visual acuity and ocular complications were evaluated. The laser procedure was quick and relatively easy, with minimal manipulation of tissues; complications were clinically insignificant. At the last follow-up, a marked IOP-lowering effect compared to baseline was observed (from 24.8 +/- 2.0 to 16.9 +/- 2.1 mm Hg; -31.8%, p interno excimer laser trabeculotomy seems effective to decrease IOP, serves to reduce the number of antiglaucoma medications and is relatively safe, proving to be a promising therapeutic option in glaucoma surgery. Copyright 2006 S. Karger AG, Basel.

  2. ArF excimer laser-induced deposition of Ag/C nanocomposite thin films in the presence of n-Hexane

    Energy Technology Data Exchange (ETDEWEB)

    Gondal, Mohammed Ashraf, E-mail: magondal@kfupm.edu.sa [Laser Research Group, Physics Department and Center of Excellence in Nanotechnology, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Fajgar, Radek [Institute of Chemical Process Fundamentals, 16502 Prague (Czech Republic); Chang, Xiaofeng [Laser Research Group, Physics Department and Center of Excellence in Nanotechnology, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Institute of Chemical Process Fundamentals, 16502 Prague (Czech Republic); College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 211100 (China); Shen, Kai [College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 211100 (China); Xu, Qingyu [Department of Physics, Southeast University, Nanjing 211189 (China)

    2014-08-30

    Highlights: • A new excimer laser ablation process was proposed to fabricate Ag/C thin film. • The size of Ag nanoparticles is ranging from 5 to 20 nm. • The ratios of Ag to C can be controlled by adjusting the pressure of n-Hexane. • The graphite-like structure of carbonaceous products was confirmed. - Abstract: Ag/C nanocomposite thin films with different Ag/C molar ratios have been prepared using ArF excimer laser-induced ablation process and silver target under n-Hexane atmosphere. The morphology, crystal structure and composition of as-deposited Ag/C nanocomposite thin films were investigated with high resolution electronic microscopic techniques (including scanning electron microscopy and transmission electron microscopy) and energy-dispersive X-ray spectroscopy, respectively. Laser Raman spectroscopy and Fourier transform infrared spectroscopy techniques were also applied to characterize the final carbonaceous products generated from n-Hexane under laser ablation process. The optical emission of the plume caused by the interaction between excimer laser and silver target in the presence of n-Hexane was studied to understand the possible reaction process. The UV–vis absorption of as-deposited Ag/C thin films, which is attributed to the surface plasmonic excitation, was also investigated in the present work.

  3. Surface studies on benzophenone doped PDMS microstructures fabricated using KrF excimer laser direct write lithography

    Energy Technology Data Exchange (ETDEWEB)

    Kant, Madhushree Bute; Shinde, Shashikant D. [Department of Physics, University of Pune, Pune 411007 (India); Bodas, Dhananjay [Centre for Nanobioscience, Agharkar Research Institute, Agharkar road, Pune 411004 (India); Patil, K.R. [Center for Materials Characterization, National Chemical Laboratories, Pune 411008 (India); Sathe, V.G. [UGC DAE Inter University Consortium, Indore 452017 (India); Adhi, K.P. [Department of Physics, University of Pune, Pune 411007 (India); Gosavi, S.W., E-mail: swg@physics.unipune.ac.in [Department of Physics, University of Pune, Pune 411007 (India)

    2014-09-30

    Graphical abstract: - Highlights: • Use of KrF Laser micromachining for Lab-On-Chip applications at lower fluence. • Addition of Benzophenone in PDMS enhances its self development sensitivity. • Benzophenone helps efficient energy transfer for equal density of bond scissioning. • Correlation of chemical composition with laser dose and microstructure. • Microstructures with well defined clean sidewalls. - Abstract: This paper discusses microfabrication process for benzophenone doped polydimethylsiloxane (PDMS) using laser lithography. KrF excimer laser of 248 nm with 20 ns pulse width at repetition rate of 1 Hz was used for microfabrication of undoped and benzophenone doped PDMS. The doped-PDMS shows sensitivity below 365 nm, permitting processing under ambient light. The analysis of etch depth revealed that doped PDMS shows self developable sensitivity at lower fluence of ∼250 mJ/cm{sup 2}. The unexposed and exposed surface was studied using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and Scanning electron microscopy (SEM). Spectrocopic analysis indicated increase in C-O, C=O, Si-O{sub 3} and Si-O{sub 4} bonding at the expense of Si-C and Si-O{sub 2} bonds of PDMS. In case of laser exposed doped-PDMS, removal of benzophenone from probe depth of spectroscopy was observed. Whereas the surface morphology of exposed and unexposed doped-PDMS was observed to be same, indicating clean development of PDMS micropatterns. The present study indicates that addition of 3.0 wt.% benzophenone in PDMS enhance self development sensitivity of PDMS. The self developable results on doped-PDMS are quite encouraging for its potential use in point of care Lab-On-Chip applications, for fabricating micropatterns using direct write laser lithography technology.

  4. Early outcome of high energy Laser (Excimer) facilitated coronary angioplasty ON hARD and complex calcified and balloOn-resistant coronary lesions: LEONARDO Study

    Energy Technology Data Exchange (ETDEWEB)

    Ambrosini, Vittorio; Sorropago, Giovanni; Laurenzano, Eugenio [Montevergine Clinic, Mercogliano (Italy); Golino, Luca, E-mail: lucagolino.jazz@alice.it [Montevergine Clinic, Mercogliano (Italy); Moriggia-Pelascini Hospital, Gravedona, Como (Italy); Casafina, Alfredo; Schiano, Vittorio [Montevergine Clinic, Mercogliano (Italy); Gabrielli, Gabriele [University Hospital Ospedali Riuniti, Ancona (Italy); Ettori, Federica; Chizzola, Giuliano [Spedali Civili University Hospital, Brescia (Italy); Bernardi, Guglielmo; Spedicato, Leonardo [University Hospital S. Maria Misericordia, Udine (Italy); Armigliato, Pietro [Istituto Italiano Ricerche Mediche, Verona (Italy); Spampanato, Carmine [Telethon Institute of Genetics and Medicine (TIGEM), Naples (Italy); Furegato, Martina [Istituto Italiano Ricerche Mediche, Verona (Italy)

    2015-04-15

    Aim: An innovative xenon–chlorine (excimer) pulsed laser catheter (ELCA X80) has been recently used for the treatment of complex coronary lesions, as calcified stenosis, chronic total occlusions and non-compliant plaques. Such complex lesions are difficult to adequately treat with balloon angioplasty and/or intracoronary stenting. The aim of this study was to examine the acute outcome of this approach on a cohort of patients with coronary lesions. Methods and Results: Eighty patients with 100 lesions were enrolled through four centers, and excimer laser coronary angioplasty was performed on 96 lesions (96%). Safety and effectiveness data were compared between patients treated with standard laser therapy and those treated with increased laser therapy. Laser success was obtained in 90 lesions (93.7%), procedural success was reached in 88 lesions (91.7%), and clinical success in was obtained in 87 lesions (90.6%). There was no perforation, major side branch occlusion, spasm, no-reflow phenomenon, dissection nor acute vessel closure. Increased laser parameters were used successfully for 49 resistant lesions without complications. Conclusions: This study suggests that laser-facilitated coronary angioplasty is a simple, safe and effective device for the management of complex coronary lesions. Furthermore, higher laser energy levels delivered by this catheter improved the device performance without increasing complications. - Highlights: • We planned this multicenter study to examine the acute outcome of an innovative xenon–chlorine (excimer) pulsed laser catheter (ELCA X80) for treatment of complex coronary lesions. • We enrolled 80 patients with 100 lesions and performed excimer laser coronary angioplasty in 96 lesions (96%). • Laser success was obtained in 90 lesions (93.7%), procedural success was reached in 88 lesions (91.7%), and clinical success was obtained in 87 lesions (90.6%). • Increased laser parameters were used successfully for 49 resistant

  5. Combined hydrogel inlay and laser in situ keratomileusis to compensate for presbyopia in hyperopic patients: one-year safety and efficacy.

    Science.gov (United States)

    Chayet, Arturo; Barragan Garza, Enrique

    2013-11-01

    To perform a feasibility study of the safety and efficacy of a corneal-contouring inlay with concurrent laser in situ keratomileusis (LASIK) to treat hyperopic presbyopia. Private clinic, Tijuana, Mexico. Prospective interventional case series. Hyperopic patients received LASIK in both eyes and a corneal inlay under the femtosecond laser flap in the nondominant eye. The inlay is designed to reshape the anterior corneal curvature, creating a near-center multifocal refractive effect. Main safety outcomes were retention of preoperative corrected distance and near visual acuities and reports of adverse events. Efficacy was determined through measurements of near, intermediate, and distance visual acuities and patient questionnaires on visual task ability and satisfaction. The study enrolled 16 patients. All eyes with an inlay achieved an uncorrected near visual acuity (UNVA) of 20/32 or better by the 1-week postoperative examination and at every visit thereafter. The mean monocular and binocular UNVA was 20/27 or better at all visits. The mean binocular uncorrected distance visual acuity improved significantly from 20/53 preoperatively to 20/19 postoperatively (P<10(-5)). One inlay was explanted during the study. At 1 year, all 14 patients analyzed were satisfied or very satisfied with their near, distance, and overall vision. The hydrogel corneal inlay with concurrent LASIK improved uncorrected near, intermediate, and distance visual acuity in hyperopic presbyopic patients with high patient satisfaction and visual task ability. This represents a new indication for this recently developed technology. Copyright © 2013 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  6. Measurement of radiation and temperature of cathod spots in excimer laser discharge; Ekishima reza reiki hodennai ni fukumareru inkyoku kiten no kogakuteki kansoku to ondo no sokutei

    Energy Technology Data Exchange (ETDEWEB)

    Minamitani, Y.; Nakatani, H. [Mitsubishi Electric Corp., Tokyo (Japan)

    1996-08-20

    Excimer laser is used in various fields such as luminous source for steppers, annealing treatment, ablation process, nuclear fusion and so on. In this paper, the radiation timing and gas temperature of cathode spots, streamer discharges and glow discharges in KrF excimer are measured by observing the radiating spectra thereof. The following conclusions are obtained from the results of the present study. Cathode spots begin to radiate at about 20ns after the discharge initiation, then the first and second radiation peaks are observed respectively when the discharge current reversing after passing zero point and the reserved discharged current approaching zero point. Streamer discharge makes flashover between electrodes at the second radiation peak of cathode spots, while the glow discharges almost disappear when streamer discharges occurring. The temperatures of cathode spots and glow discharge as 5500K and 2600K respectively are almost constant and independent upon the discharging voltage of laser. 14 refs., 12 figs.

  7. Chaînes laser intenses à contraste élevé par amplification directe dans un milieu gazeux à excimères*

    Science.gov (United States)

    Uteza, O.; Tcheremiskine, V.; Clady, R.; Coustillier, G.; Gastaud, M.; Sentis, M.; Mikheev, L. D.; Chambaret, J. P.

    2006-12-01

    Cet article présente l'intérêt du concept de laser hybride (solide/gaz) et de l'amplification directe de puissance dans un milieu à excimères pour les chaînes laser de puissance ultrabrèves à contraste élevé. L'architecture d'une chaîne laser multiterawatt basée sur l'emploi du milieu amplificateur XeF(C-A) pompé par voie photolytique est ensuite détaillée, ainsi que les perspectives de dimensionnement de cette approche au niveau PWetEW.

  8. Morphological and structural modifications induced in a-Si{sub 1-x} C{sub x}:H films by excimer laser annealing

    Energy Technology Data Exchange (ETDEWEB)

    Coscia, U. [CNISM Unita' di Napoli, Complesso Universitario MSA, Napoli (Italy); Universita di Napoli ' Federico II' , Dipartimento di Scienze Fisiche, Napoli (Italy); Ambrosone, G. [Universita di Napoli ' Federico II' , Dipartimento di Scienze Fisiche, Napoli (Italy); CNR-SPIN, Napoli (Italy); Basa, D.K. [Utkal University, Department of Physics, Bhubaneswar (India); Tresso, E. [Politecnico di Torino, Dipartimento di Scienza dei Materiali ed Ingegneria Chimica, Turin (Italy); Chiodoni, A. [IIT rate at POLITO - Center for Space Human Robotics, Turin (Italy); Pinto, N.; Murri, R. [Universita' di Camerino, Dipartimento di Fisica, Camerino (Italy)

    2010-09-15

    Hydrogenated amorphous silicon carbon films of different carbon content deposited by plasma enhanced chemical vapour deposition on Corning glass and crystalline silicon substrates have been irradiated by an excimer (KrF) laser. The properties of these samples were investigated by X-ray diffraction, field emission scanning electron microscopy and Fourier transform infrared spectroscopy before and after laser treatment, in order to understand the role of the carbon content as well as the substrate in the structural modifications. It has been demonstrated that the changes induced in the films by the laser treatment are independent of the substrate but depend on the carbon content which facilitates the crystallization process. (orig.)

  9. Complicações per e pós-operatórias em 1000 olhos submetidos a LASIK An analysis of intraoperative and postoperative complications in 1000 laser in situ keratomileusis cases

    Directory of Open Access Journals (Sweden)

    Telma Pereira

    2001-11-01

    Full Text Available Objetivo: Analisar a incidência, tipo, tratamento e evolução das complicações em LASIK. Métodos: Estudo retrospectivo de 1000 olhos submetidos a LASIK usando os microceratótomos Hansatome® ou Automated Corneal Shaper® e os aparelhos de Excimer Laser VISX 20/20B ou Chiron Technolas 217C. Complicações peroperatórias e pós-operatórias precoces e tardias foram analisadas. Resultados: A média do equivalente esférico pré-operatório foi de -4,29 ± 3,20D. A média do seguimento foi de 6,05 ± 6,69 meses. No período peroperatório foram encontradas cinco (0,5% complicações do disco relacionadas ao microceratótomo (3 discos finos, 1 disco com perfuração central e 1 disco pequeno. As complicações mais freqüentes no período pós-operatório precoce foram as dobras de disco (6,4%, seguidas de debris na interface (4,1%, ceratite não específica da interface (1,1%, "haze" (0,4%, crescimento epitelial da interface (0,4% e deslocamento de disco (0,3%. A maioria destes eventos foi prontamente tratada, alcançando-se bons resultados. Para as complicações tardias, relacionadas à refração, foram analisados 655 olhos que apresentavam seguimento mínimo de 3 meses. No último exame, a média do equivalente esférico neste grupo foi de -0,26±0,76D. Oito por cento dos olhos encontravam-se com hipocorreção superior a 1,00D; e 1,67% com hipercorreção > 1,00D. Retratamento foi necessário em 28 olhos (4,27%. Cinco casos (0,76% perderam de 2 ou mais linhas da melhor acuidade visual corrigida. Não foram observadas outras complicações visualmente importantes. Conclusão: LASIK é um procedimento refrativo seguro e com poucas complicações.Purpose: To analyze the incidence, type, management and evolution of complications in laser in situ keratomileusis (LASIK. Methods: Retrospective non-comparative case series. LASIK was performed in 1000 eyes using the Hansatome® or the Automated Corneal Shaper® microkeratomes, and the VISX 20/20B

  10. INDEPENDENT EVALUATION OF THE GAM EX5ALN MINIATURE LINE-NARROWED KRF EXCIMER LASER

    Science.gov (United States)

    2017-06-01

    Bookmark not defined. 2: Ex5ALN KrF laser wavelength study. The laser output was recorded at 248.7 nm relative to the Hg atomic emission at 253.7 nm...Error! Bookmark not defined. 3: Ex5ALN KrF laser pulse width versus accumulated pulses for 14 kV discharge at 100 Hz...Error! Bookmark not defined. 4: Ex5ALN KrF laser timing jitter of laser

  11. Numerical study of threshold intensity dependence on gas pressure in the breakdown of molecular hydrogen induced by excimer laser

    Science.gov (United States)

    Gamal, Yosr E. E.-D.; Nassef, O. Aied

    2017-10-01

    In the present work, a numerical analysis is performed to investigate the threshold intensity dependence on gas pressure in laser spark ignition of the H2 plasma. The analysis considered the experimental measurements that were carried out by Yagi and Huo [Appl. Opt. 35, 3183 (1996)]. In their experiment, H2 in a pressure range of 150-3000 Torr is irradiated by a focused excimer laser source using a 96 cm lens at a wavelength of 248 nm and a pulse duration of 20 ns. The study, based on a modified electron cascade model [K. A. Hamam et al., J. Mod. Phys. 4, 311 (2013)], solves numerically a time-dependent energy equation for the distribution of the electron energy as well as a set of rate equations that describe the change in the formed excited molecule population. This model enabled the determination of the threshold intensity as a function of gas pressure. The validity of the model was tested by comparing the calculated thresholds with the experimentally measured ones. Moreover, the calculation of the electron energy distribution function and its parameters justified the role of the electron gain and loss processes in controlling the value of threshold intensity in relation to the gas pressure. The effect of loss processes on the threshold intensity is also presented.

  12. NC-controlled production of smooth 3D surfaces in brittle materials with 193-nm excimer laser

    Science.gov (United States)

    Toenshoff, Hans K.; Graumann, Christoph; Hesener, Hanno; Rinke, Marcus

    1998-08-01

    Micromachining performed by Excimer Lasers in conjunction with NC-controlled machines offer flexible production possibilities for 3-D-surfaces. Due to the limitations of conventional micromachining technology for brittle transparent materials in the micro range, a new laser machining beam guiding and data handling system was designed and built. The data handling starts with the mathematical description of the surface shape to be machined. The contour can be derived from a mathematical function or individual xyz-data point information from any CAD-program. A pre-processor calculates the nc-data for laser triggering, xyz-motion and the nc-mask control. Each laser pulse leads to a material removal, defined by the illuminated surface on the work piece as well as the energy density. The principal of superposition of pulses allows the creation of the desired contour. The chosen ablation strategy determines the surface roughness and the process speed. To achieve best results, it has to be carefully adjusted for a specific material. This technique does not require prefabricated tools such as semiconductor masks. This is a sufficient method for structuring grooves in ceramics, diamonds or glass as well as aspherical transparent optical surfaces or micro lens arrays. The excellent absorption of 193 nm compared to 248 nm or larger wavelengths leads to damage free structuring of most brittle materials. The optimized surface ablation process requires spot sizes and energy densities on the work piece which can not be realized with a mirror based beam guidance system. To eliminate these restrictions, a new mirror free machining concept with a gas flushed beam guiding system mounted on a granite vibration reduction table with air bearing positioning system was build. This paper describes the potential of 193 nm treatment of 3-D micro surfaces with a process optimized machine and data handling system.

  13. Comparison of a hydrogel corneal inlay and monovision laser in situ keratomileusis in presbyopic patients: focus on visual performance and optical quality

    Directory of Open Access Journals (Sweden)

    Verdoorn C

    2017-09-01

    Full Text Available Cornelis Verdoorn Lasik Centrum Eye Clinic, Boxtel, the Netherlands Purpose: To compare the visual performance and optical quality after Raindrop Near Vision Inlay implantation or monovision LASIK for the correction of presbyopia. Materials and methods: In this retrospective case-series study, patients previously treated in the nondominant eye with monovision LASIK were compared with patients previously implanted with Raindrop Near Vision Inlay. The study enrolled 16 inlay and 15 monovision LASIK patients. Uncorrected near visual acuity, uncorrected distance visual acuity, binocular stereopsis, patient satisfaction, and patient task performance were assessed. Results: Postoperatively, the mean spherical equivalent was -0.66 D (0.78 SD for the inlay group and -1.03 D (0.56 SD for the monovision LASIK group. Monocularly, at uncorrected near distances, 60% of inlay patients and 47% of monovision LASIK patients achieved ≥20/20. Monocularly, at uncorrected far distances, 75% of inlay patients and 40% of monovision LASIK patients achieved ≥20/32 vision. Binocularly, at near distances, 79% of inlay patients and 53% of monovision LASIK patients obtained ≥20/20 vision. All patients achieved ≥20/20 binocularly for distance. On average, inlay patients obtained 98 seconds of arc and monovision LASIK patients obtained 286 seconds of arc for stereopsis. Most (79% of the inlay patients and 66% of monovision LASIK patients were satisfied with their near vision, while 86% of inlay patients and 67% of monovision LASIK patients were satisfied with their distance vision. Conclusion: Patients receiving corneal inlays demonstrated better near and distance visual acuities, binocular stereopsis, task performance, and satisfaction, when compared to patients treated with monovision LASIK. Keywords: presbyopia, corneal inlays, monovision, laser in situ keratomileusis, LASIK, Raindrop Near Vision Inlay

  14. Alterations of extracellular matrix components and proteinases in human corneal buttons with INTACS for post-laser in situ keratomileusis keratectasia and keratoconus.

    Science.gov (United States)

    Maguen, Ezra; Rabinowitz, Yaron S; Regev, Lee; Saghizadeh, Mehrnoosh; Sasaki, Takako; Ljubimov, Alexander V

    2008-06-01

    To perform an immunohistochemical evaluation of corneas with INTACS for post-laser in situ keratomileusis (LASIK) keratectasia and keratoconus, obtained after corneal transplantation. Corneas from 1 patient with INTACS for post-LASIK keratectasia and 2 patients with INTACS for keratoconus were obtained within 3 hours after penetrating keratoplasty, and cryostat sections were analyzed by immunostaining for 35 extracellular matrix (ECM) components and proteinases. In the stroma of all corneas next to an INTACS implant, ECM components typically associated with fibrosis were observed. These included tenascin-C, fibrillin-1, and types III, IV (alpha1/alpha2 chains), and XIV collagen. Also, significant deposition of perlecan, nidogen-2, and cellular fibronectin was revealed in the same locations. The keratoconus cases displayed typical Bowman layer breaks and subepithelial fibrosis with deposition of various ECM components. In all cases, some keratocytes around INTACS were positive for specific proteinases associated with stromal remodeling, including cathepsins F and H, matrix metalloproteinase (MMP)-1, MMP-3, and MMP-10. Staining for MMP-7 was variable; MMP-2 and MMP-9 were mostly negative. Patterns of type IV collagen alpha 3, alpha 4, and alpha 6 chains; types VI and VIII collagen; laminin-332, alpha 4, alpha 5, beta1, beta2, and gamma 1 laminin chains; vitronectin; thrombospondin-1; urokinase; EMMPRIN; and cathepsins B and L were unchanged around INTACS in all 3 cases compared with normal. Abnormal accumulation of fibrotic ECM components and proteinases near INTACS suggests ongoing lysis and remodeling of corneal stroma. Specific changes observed in each case may be related to underlying pathology.

  15. Effect of femtosecond and microkeratome flaps creation on the cornea biomechanics during laser in situ keratomileusis: one year follow-up

    Science.gov (United States)

    Sun, Qian; Deng, Zheng-Zheng; Zhou, Yue-Hua; Zhang, Jing; Peng, Xiao-Yan

    2016-01-01

    AIM To compare the corneal biomechanical outcomes at one year after laser in situ keratomileusis (LASIK) with the flaps created by Ziemer and Moria M2 microkeratome with 110 head and -20 blade. METHODS Totally 100 eyes of 50 consecutive patients were enrolled in this prospective study and divided into two groups for corneal flaps created by ZiemerFemto LDV and Moria M2 microkeratome with 110 head and -20 blade. Corneal biomechanical properties including cornea resistance factor (CRF) and cornea hysteresis (CH) were measured before and 1, 3, 6, 12mo after surgery by ocular response analyzer. Central cornea thickness and corneal flap thickness were measured by optical coherence tomography. RESULTS The ablation depth (P=0.693), residual corneal thickness (P=0.453), and postoperative corneal curvature (P=0.264) were not significant different between Ziemer group and Moria 110-20 group after surgery. The residual stromal bed thickness, corneal flap thickness, CH and CRF at 12mo after surgery were significant different between Ziemer group and Moria 110-20 group (Pbiomechanical results. The CRF and CH increased gradually from 1 to 12mo after surgery in Ziemer group, increased from 1 to 6mo but decreased from 6 to 12mo in Moria 110-20 group. Both CRF and CH at one year after surgery increased with the increasing of residual cornea thickness; pre-LASIK CRF, CRF also increased with residual stromal bed thickness, while CH decreased with the increasing of pre-LASIK intraocular pressure and cornea flap thickness (Pcornea flaps with stable cornea biomechanics than mechanical microkeratome. PMID:27803856

  16. One-year results of simultaneous laser in situ keratomileusis and small-aperture corneal inlay implantation for hyperopic presbyopia: comparison by age.

    Science.gov (United States)

    Tomita, Minoru; Waring, George O

    2015-01-01

    To compare by age the safety, efficacy, and patient satisfaction after simultaneous laser in situ keratomileusis (LASIK) and small-aperture corneal inlay implantation (Kamra) for hyperopic presbyopia. Shinagawa LASIK Center, Tokyo, Japan. Retrospective comparative cohort study. Simultaneous LASIK and small-aperture corneal inlay implantation were performed in the nondominant eye of hyperopic presbyopic patients with astigmatism. Patients were divided into groups by age as follows: Group 1 (40 to 49 years), Group 2 (50 to 59 years), and Group 3 (60 to 65 years). The uncorrected (UDVA) and corrected (CDVA) distance visual acuities, uncorrected near visual acuity (UNVA), and patient questionnaire results were compared. The study evaluated 277 eyes of 277 patients. All groups achieved a mean UDVA of 20/20, with Group 1, Group 2, and Group 3 gaining 1 line, 2 lines, and 3 lines, respectively. The mean UNVA was J2 with 4 lines gained in Group 1 and J3 with 5 lines gained in Group 2 and Group 3. The mean CDVA and corrected near visual acuity remained the same as at baseline. Simultaneous LASIK and small-aperture corneal inlay implantation for hyperopic presbyopia was a safe and effective treatment option. Although the outcomes were comparable between groups, Group 3 had the largest gain in UDVA and UNVA and the highest patient satisfaction, despite having the lowest reduction in dependence on reading glasses. Taking age into account might help achieve optimum postoperative outcomes and improved patient satisfaction. Dr. Tomita is a consultant to Ziemer Ophthalmic Systems AG, Acufocus, Inc., and Schwind eye-tech-solutions GmbH and Co. KG. Dr. Waring is a consultant to Acufocus, Inc. Copyright © 2015 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  17. Changes in biomechanical properties of the cornea and intraocular pressure after myopic laser in situ keratomileusis using a femtosecond laser for flap creation determined using ocular response analyzer and Goldmann applanation tonometry.

    Science.gov (United States)

    Shin, Jonghoon; Kim, Tae Won; Park, Soo Jeong; Yoon, Min; Lee, Ji Woong

    2015-03-01

    To compare intraocular pressure (IOP) measurements before and after laser in situ keratomileusis (LASIK) using a femtosecond laser for flap creation, and to identify factors that may influence the preoperative and postoperative IOP, and the change in IOP after LASIK. Forty eyes from 20 patients who underwent treatment for myopia using a femtosecond laser for flap creation were enrolled in this study. The IOP and corneal biomechanical markers were prospectively measured preoperatively and 1 month after LASIK with Goldmann applanation tonometry (GAT) and the ocular response analyzer (ORA). Manifest refraction spherical equivalent, central corneal thickness, ablation depth, and mean corneal curvature (K reading) were also recorded. After LASIK, there was a significant reduction in the IOP measurement with respect to the corneal-compensated intraocular pressure (IOPcc) (Δ=-0.67±2.07 mm Hg), Goldmann-correlated pressure (IOPg) (Δ=-3.92±2.19 mm Hg), and GAT (Δ=-2.6±2.51). Multiple regression analysis revealed that the corneal hysteresis (CH) and corneal resistance factor (CRF) are statistically significant predictors of IOPcc, IOPg, and GAT (Pcorneal thickness significantly predicted ΔGAT (adjusted R²=0.464). ORA provides a more complete measurement of IOP after LASIK with a femtosecond laser than GAT because ORA provides greater knowledge of the corneal biomechanics in terms of CH and CRF.

  18. Absorption of 308-nm excimer laser radiation by balanced salt solution, sodium hyaluronate, and human cadaver eyes

    Energy Technology Data Exchange (ETDEWEB)

    Keates, R.H.; Bloom, R.T.; Schneider, R.T.; Ren, Q.; Sohl, J.; Viscardi, J.J. (Univ. of California, Irvine (USA))

    1990-11-01

    Absorption of the excimer laser radiations of 193-nm argon fluorine and 308-nm xenon chloride in balanced salt solution, sodium hyaluronate, and human cadaver eyes was measured. The absorption of these materials as considerably different for the two wavelengths; we found that 308-nm light experienced much less absorption than the 193-nm light. The extinction coefficient (k) for 308 nm was k = 0.19/cm for balanced salt solution and k = 0.22/cm for sodium hyaluronate. In contrast to this, the extinction coefficient for 193 nm was k = 140/cm for balanced salt solution and k = 540/cm for sodium hyaluronate. Two 1-day-old human phakic cadaver eyes showed complete absorption with both wavelengths. Using aphakic eyes, incomplete absorption was noted at the posterior pole with 308 nm and complete absorption was noted with 193 nm. The extinction in the anterior part of aphakic eyes (the first 6 mm) was 4.2/cm for 308 nm, meaning that the intensity of the light is reduced by a factor of 10 after traveling the first 5.5 mm. However, we observed that the material in the eye fluoresces, meaning the 308 nm is transformed into other (longer) wavelengths that travel through the total eye with minimal absorption. Conclusions drawn from this experiment are that the use of the 308-nm wavelength may have undesirable side effects, while the use of the 193-nm wavelength should be consistent with ophthalmic use on both the cornea and the lens.

  19. A retrospective analysis of the postoperative use of loteprednol etabonate gel 0.5% following laser-assisted in situ keratomileusis or photorefractive keratectomy surgery

    Directory of Open Access Journals (Sweden)

    Salinger CL

    2015-11-01

    Full Text Available Clifford L Salinger,1 Michael Gordon,2 Mitchell A Jackson,3 Theodore Perl,4 Eric Donnenfeld5 1VIP Laser Eye Center, Palm Beach Gardens, FL, 2Gordon Weiss Schanzlin Vision Institute, San Diego, CA, 3Jacksoneye, Lake Villa, IL, 4Corneal Associates of New Jersey, Fairfield, NJ, 5Ophthalmic Consultants of Long Island, Garden City, NY, USA Background: While loteprednol etabonate ophthalmic gel 0.5% (LE gel is approved for treatment of postoperative ocular inflammation and pain, there have been no reported studies in patients undergoing laser-assisted in situ keratomileusis (LASIK or photorefractive keratectomy (PRK.Methods: This was a retrospective chart review conducted at five refractive surgical centers in the USA. Data were collected from primary LASIK or PRK surgery cases in which LE gel was used postoperatively as the clinician’s routine standard of care and in which patients were followed-up for up to 6 months. Data extracted from charts included patient demographics, surgical details, LE gel dosing regimen, pre- and postsurgical refractive characteristics, intraocular pressure (IOP measurements, and visual acuity. Primary outcomes included postoperative IOP elevations, adverse events, and early discontinuations.Results: Data were collected on 189 LASIK eyes (96 patients and 209 PRK eyes (108 patients. Mean (standard deviation [SD] years of age at surgery was 36.0 (11.7 and 33.9 (11.3 in LASIK and PRK patients. LE gel was prescribed most often four times daily during the first postoperative week, regardless of procedure; the most common treatment duration was 7–14 days in LASIK and ≥30 days in PRK patients. No unusual corneal findings or healing abnormalities were reported. Mean postoperative uncorrected distance visual acuity was 20/24 in LASIK and 20/30 in PRK eyes. Mild/trace corneal haze was reported in 20% of PRK patients; two PRK patients with moderate/severe corneal haze were switched to another corticosteroid. Mean postoperative

  20. Small incision lenticule extraction (SMILE) versus laser in-situ keratomileusis (LASIK): study protocol for a randomized, non-inferiority trial.

    Science.gov (United States)

    Ang, Marcus; Tan, Donald; Mehta, Jodhbir S

    2012-05-31

    Small incision lenticule extraction or SMILE is a novel form of 'flapless' corneal refractive surgery that was adapted from refractive lenticule extraction (ReLEx). SMILE uses only one femtosecond laser to complete the refractive surgery, potentially reducing surgical time, side effects, and cost. If successful, SMILE could potentially replace the current, widely practiced laser in-situ keratomileusis or LASIK. The aim of this study is to evaluate whether SMILE is non-inferior to LASIK in terms of refractive outcomes at 3 months post-operatively. Single tertiary center, parallel group, single-masked, paired-eye design, non-inferiority, randomized controlled trial. Participants who are eligible for LASIK will be enrolled for study after informed consent. Each participant will be randomized to receive SMILE and LASIK in each eye. Our primary hypothesis (stated as null) in this non-inferiority trial would be that SMILE differs from LASIK in adults (>21 years old) with myopia (> -3.00 diopter (D)) at a tertiary eye center in terms of refractive predictability at 3 months post-operatively. Our secondary hypothesis (stated as null) in this non-inferiority trial would be that SMILE differs from LASIK in adults (>21 years old) with myopia (> -3.00 D) at a tertiary eye center in terms of other refractive outcomes (efficacy, safety, higher-order aberrations) at 3 months post-operatively. Our primary outcome is refractive predictability, which is one of several standard refractive outcomes, defined as the proportion of eyes achieving a postoperative spherical equivalent (SE) within ±0.50 D of the intended target. Randomization will be performed using random allocation sequence generated by a computer with no blocks or restrictions, and implemented by concealing the number-coded surgery within sealed envelopes until just before the procedure. In this single-masked trial, subjects and their caregivers will be masked to the assigned treatment in each eye. This novel

  1. Evaluation of Biomechanical Changes in Myopia Patients with Unsatisfactory Corneas After Femto Second-Laser In Situ Keratomileusis (FS-LASIK) Concurrent with Accelerated Corneal Collagen Cross-Linking Using Corvis-ST: Two-Year Follow-Up Results.

    Science.gov (United States)

    Xu, Weiwei; Tao, Ye; Wang, Liqiang; Huang, Yifei

    2017-07-27

    BACKGROUND Some myopia patients with unsatisfactory corneas consider corneal refractive surgery for different reasons. Accelerated corneal collagen crosslinking (ACXL) is an effective method to enhance the resistance of the cornea. The present investigation was designed to evaluate the changes of biomechanical properties in patients with myopia and thin corneas after femtosecond-laser in situ keratomileusis (FS-LASIK) concurrent with ACXL. MATERIAL AND METHODS A prospective study was designed. A total of 22 eyes of 11 myopia astigmatism patients with unsatisfactory corneas were enrolled. The patients were assigned to femtosecond-laser in situ keratomileusis concurrent with accelerated corneal collagen crosslinking (FS-LASIK-ACXL). The follow-up duration was 24 months. Manifest refraction, uncorrected (UDVA), and corrected distance visual acuity (CDVA), ultra-high-speed camera (Corvis-ST), corneal topography, anterior segment OCT (AS-OCT), Pentacam, and endothelial cell density (ECD) were examined before and after the operation. The corneal biomechanical and refractive data was analyzed using SAS9.3. Data were analyzed through normal distribution test and variance of analysis. The difference was considered as statistically significant when pcorneas, and it does not increase the risk of iatrogenic keratectasia.

  2. LASEK for the correction of hyperopia with mitomycin C using SCHWIND AMARIS excimer laser: one-year follow-up

    Directory of Open Access Journals (Sweden)

    Khosrow Jadidi

    2015-11-01

    Full Text Available AIM: To evaluate the efficacy, safety and predictability of laser-assisted sub-epithelial keratectomy(LASEKfor the correction of hyperopia using the SCHWIND AMARIS platform.METHODS: This retrospective single-surgeon study includes 66 eyes of 33 patients with hyperopia who underwent LASEK with mitomycin C(MMC. The median age of patients was 35.42±1.12y(ranging 18 to 56y. In each patient LASEK was performed using SCHWIND AMARIS excimer laser. Postoperatively clinical outcomes were evaluated in terms of predictability, safety, efficacy, subjective and objective refractions, uncorrected visual acuity(UCVA, best spectacle-corrected visual acuity(BSCVAand adverse events. RESULTS: The mean baseline refraction was 3.2±1.6 diopters(D(ranging 0 to 7 D. The mean pre-operative and postoperative spherical equivalent(SEwere 2.34±1.76(ranging -1.25 to 7 Dand 0.30±0.84(ranging -0.2 to 0.8 Drespectively(P=0.001. The mean hyperopia was 0.63±0.84 D(ranging -1.75 to 2.76 D6 to 12mo postoperatively. Likewise, the mean astigmatism was 0.68±0.43 D(range 0 to 2 Dwith 51(77.3%and 15(22.7%eyes within ±1 and ±0.50 D respectively. The safety index and efficacy index were 1.08 and 1.6 respectively.CONCLUSION:LASEK using SCHWIND AMARIS with MMC yields good visual and refractive results for hyperopia. Moreover, there were no serious complications.

  3. Chitosan- and polypropylene-oriented surface modification using excimer laser and their biocompatibility study.

    Science.gov (United States)

    Khaledian, Mohammad; Jiroudhashemi, Faeze; Biazar, Esmaeil

    2017-02-01

    Surface modification of medical polymers is carried out to improve biocompatibility. In this study, conventional polymers (chitosan and polypropylene) were modified to laser at different features (oriented and non-oriented) to create a vast range of physicochemical characteristics on the surface of polymers and investigate their effects on biocompatibility of treated surfaces. Atomic force microscope (AFM) was applied to study the morphology of treated samples in comparison with those of the untreated PS. Contact angle analyses were used to evaluate the wettability and surface energy of the treated films. AFM studies showed that after laser treatment, some distinctive nanostructures are created on the surface of polymers. The data from contact angle measurements demonstrated that laser irradiation created surfaces with a vast range of properties in the wettability point of view. The cellular results revealed that after surface modification by laser irradiation, biocompatibility of polymeric films, especially oriented films was enhanced.

  4. A prospective comparison of phakic collamer lenses and wavefront-optimized laser-assisted in situ keratomileusis for correction of myopia

    Directory of Open Access Journals (Sweden)

    Parkhurst GD

    2016-06-01

    Full Text Available Gregory D Parkhurst1,2 1Refractive Surgery Center, Carl R Darnall Army Medical Center, Fort Hood, 2Parkhurst NuVision, San Antonio, TX, USA Purpose: The aim of this study was to evaluate and compare night vision and low-luminance contrast sensitivity (CS in patients undergoing implantation of phakic collamer lenses or wavefront-optimized laser-assisted in situ keratomileusis (LASIK.Patients and methods: This is a nonrandomized, prospective study, in which 48 military personnel were recruited. Rabin Super Vision Test was used to compare the visual acuity and CS of Visian implantable collamer lens (ICL and LASIK groups under normal and low light conditions, using a filter for simulated vision through night vision goggles.Results: Preoperative mean spherical equivalent was –6.10 D in the ICL group and –6.04 D in the LASIK group (P=0.863. Three months postoperatively, super vision acuity (SVa, super vision acuity with (low-luminance goggles (SVaG, super vision contrast (SVc, and super vision contrast with (low luminance goggles (SVcG significantly improved in the ICL and LASIK groups (P<0.001. Mean improvement in SVaG at 3 months postoperatively was statistically significantly greater in the ICL group than in the LASIK group (mean change [logarithm of the minimum angle of resolution, LogMAR]: ICL =-0.134, LASIK =-0.085; P=0.032. Mean improvements in SVc and SVcG were also statistically significantly greater in the ICL group than in the LASIK group (SVc mean change [logarithm of the CS, LogCS]: ICL =0.356, LASIK =0.209; P=0.018 and SVcG mean change [LogCS]: ICL =0.390, LASIK =0.259; P=0.024. Mean improvement in SVa at 3 months was comparable in both groups (P=0.154.Conclusion: Simulated night vision improved with both ICL implantation and wavefront-optimized LASIK, but improvements were significantly greater with ICLs. These differences may be important in a military setting and may also affect satisfaction with civilian vision correction

  5. Influence of pupil diameter on the relation between ocular higher-order aberration and contrast sensitivity after laser in situ keratomileusis.

    Science.gov (United States)

    Oshika, Tetsuro; Tokunaga, Tadatoshi; Samejima, Tomokazu; Miyata, Kazunori; Kawana, Keisuke; Kaji, Yuichi

    2006-04-01

    To investigate the influence of pupil diameter on the relation between induced changes in ocular higher-order wavefront aberrations and changes in contrast sensitivity by conventional laser in situ keratomileusis (LASIK) for myopia. In 215 eyes of 117 patients (age, 33.2 +/- 8.3 years) undergoing LASIK for myopia of -1.25 to -13.5 D (-5.28 +/- 2.55 D), ocular wavefront aberrations and contrast sensitivity function were determined before and 1 month after surgery. Preoperative photopic pupil diameter was measured with a digital camera. Ocular higher-order aberrations were measured for a 4-mm pupil with a Hartmann-Shack wavefront analyzer. The root-mean-square (RMS) of the third- and fourth-order Zernike coefficients was used to represent coma- and spherical-like aberration, respectively. From the contrast-sensitivity data, the area under the log contrast sensitivity function (AULCSF) was calculated. One hundred five eyes had a photopic pupil diameter of 4 mm or larger, and the remaining 110 had a photopic pupil diameter smaller than 4 mm. There were no statistically significant differences in the background clinical data between these two groups. In the eyes with a photopic pupil diameter of 4 mm or larger, the changes in third-order comalike aberrations did not correlate with the changes in AULCSF (Pearson correlation coefficient, r = -0.037, P = 0.723) and 10% low-contrast visual acuity (r = 0.125, P = 0.224), but fourth-order spherical-like aberrations correlated significantly with the changes in AULCSF (r = -0.229, P = 0.024) and 10% low-contrast visual acuity (r = 0.221, P = 0.038). In the eyes with photopic pupil size smaller than 4 mm, there were significant correlations between the changes in comalike aberrations and the changes in AULCSF (r = -0.487, P pupil diameter, increases in spherical-like aberration dominantly affect contrast sensitivity, whereas in eyes with smaller pupil size, changes in coma-like aberration exert greater influence on visual

  6. Small Incision Lenticule Extraction (SMILE versus Femtosecond Laser-Assisted In Situ Keratomileusis (FS-LASIK for Myopia: A Systematic Review and Meta-Analysis.

    Directory of Open Access Journals (Sweden)

    Zeren Shen

    Full Text Available The goal of this study was to compare small incision lenticule extraction (SMILE with femtosecond laser-assisted in situ keratomileusis (FS-LASIK for treating myopia.The CENTRAL, EMBASE, PubMed databases and a Chinese database (SinoMed were searched in May of 2016. Twelve studies with 1,076 eyes, which included three randomized controlled trials (RCTs and nine cohorts, met our inclusion criteria. The overall quality of evidence was evaluated using the Grading of Recommendations Assessment, Development and Evaluation (GRADE working group framework. Data were extracted and analysed at three to six months postoperatively. Primary outcome measures included a loss of one or more lines of best spectacle corrected visual acuity (BSCVA, uncorrected visual acuity (UCVA of 20/20 or better, mean logMAR UCVA, postoperative mean spherical equivalent (SE and postoperative refraction within ±1.0 D of the target refraction. Secondary outcome measures included ocular surface disease index (OSDI, tear breakup time (TBUT and Schirmer's 1 test (S1T as dry eye parameters, along with corneal sensitivity.The overall quality of evidence was considered to be low to very low. Pooled results revealed no significant differences between the two groups with regard to a loss of one or more lines in the BSCVA (OR 1.71; 95% CI: 0.81, 3.63; P = 0.16, UCVA of 20/20 or better (OR 0.71; 95% CI: 0.44, 1.15; P = 0.16, logMAR UCVA (MD 0.00; 95% CI: -0.03, 0.04; P = 0.87, postoperative refractive SE (MD -0.00; 95% CI: -0.05, 0.05; P = 0.97 or postoperative refraction within ±1.0 D of the target refraction (OR 0.78; 95% CI: 0.22, 2.77; P = 0.70 within six months postoperatively. The pooled analysis also indicated that the FS-LASIK group suffered more severely from dry eye symptoms (OSDI; MD -6.68; 95% CI: -11.76, -2.00; P = 0.006 and lower corneal sensitivity (MD 12.40; 95% CI: 10.23, 14.56; P < 0.00001 at six months postoperatively.In conclusion, both FS-LASIK and SMILE are safe

  7. H and Au diffusion in high mobility a-InGaZnO thin-film transistors via low temperature KrF excimer laser annealing

    Science.gov (United States)

    Bermundo, Juan Paolo S.; Ishikawa, Yasuaki; Fujii, Mami N.; Ikenoue, Hiroshi; Uraoka, Yukiharu

    2017-03-01

    We report the fabrication of high mobility amorphous InGaZnO (a-IGZO) thin-film transistors (TFTs) irradiated by a single shot of a 248 nm KrF excimer laser. Very high mobilities (μ) of up to 43.5 cm2/V s were obtained after the low temperature excimer laser annealing (ELA) process. ELA induces high temperatures primarily in the upper layers and maintains very low temperatures of less than 50 °C in the substrate region. Scanning Transmission Electron micrographs show no laser induced damage and clear interfaces after the laser irradiation. In addition, several characterization studies were performed to determine the μ improvement mechanism. The analysis of Secondary Ion Mass Spectrometry and X-ray Photoelectron Spectroscopy suggests incorporation of H mainly from the hybrid passivation layer into the channel. Moreover, Energy-dispersive X-ray Spectroscopy results show that Au diffused into the channel after ELA. Both KrF ELA-induced H and Au diffusion contributed to the higher μ. These results demonstrate that ELA can greatly enhance the electrical properties of a-IGZO TFTs for promising applications in large area, transparent, and flexible electronics.

  8. Láser in situ keratomileusis en la corrección de miopía y astigmatismo residual posqueratotomía radial en casos seleccionados Laser in situ keratomileusis to correct myopia and residual astigmatism after radial keratotomy in selected cases

    Directory of Open Access Journals (Sweden)

    Eneida Pérez Candelaria

    2010-01-01

    Full Text Available OBJETIVO: Evaluar la seguridad y la eficacia del tratamiento con láser in situ keratomileusis en pacientes con defectos residuales posqueratotomía radial. MÉTODOS: Se realizó un estudio descriptivo de tipo prospectivo longitudinal a 55 ojos de 31 pacientes con miopía y/o astigmatismo residuales posqueratotomía radial reoperados con láser in situ keratomileusis en el Servicio de Cirugía Refractiva del Instituto Cubano de Oftalmología "Ramón Pando Ferrer" desde enero a junio del 2007. En la selección de los pacientes, se utilizaron estrictos criterios de inclusión y exclusión utilizándose las variables: error refractivo residual en equivalente esférico medio, la agudeza visual sin corrección y la mejor agudeza visual corregida preLASIK y posLASIK, así como las complicaciones transoperatorias y postoperatorias. El seguimiento promedio de los pacientes fue de 12 ± 3 meses. RESULTADOS: El equivalente esférico posLASIK disminuyó notablemente en el primer día del posoperatorio y se mantuvo estable en la última consulta. La agudeza visual sin corrección posLASIK fue 1,0 (20/20 en 22 ojos (40 % y > 0,5 (20/40 en 44 ojos (80 %. En 11 ojos (20 %, la mejor agudeza visual corregida mejoró 1 línea en la cartilla de Snellen. Se presentócomo complicación intraoperatoria un ojo con perforación central del flap corneal y dentro de las complicaciones postoperatorias se reportaron detritus y restos hemáticos en la interfase en 2 ojos, pliegues finos del colgajo en un solo ojo y epitelización de la interfase fuera del eje visual igualmente, en un solo ojo. CONCLUSIONES: El Láser in situ keratomileusis puede ser usado exitosamente en la corrección de la miopía y el astigmatismo posqueratotomía radial en casos debidamente seleccionados.OBJECTIVE: To evaluate the safety and the efficacy of the Laser in Situ Keratomileusis treatment in patients with residual defects after radial keratotomy. METHODS: A prospective, longitudinal and

  9. Mitomycin-C in corneal surface excimer laser ablation techniques: a report by the American Academy of Ophthalmology.

    Science.gov (United States)

    Majmudar, Parag A; Schallhorn, Steven C; Cason, John B; Donaldson, Kendall E; Kymionis, George D; Shtein, Roni M; Verity, Steven M; Farjo, Ayad A

    2015-06-01

    To review the published literature assessing the efficacy and safety of mitomycin-C (MMC) as an adjunctive treatment in corneal surface excimer laser ablation procedures. Literature searches of the PubMed and Cochrane Library databases were last conducted on August 19, 2014, without language or date limitations. The searches retrieved a total of 239 references. Of these, members of the Ophthalmic Technology Assessment Committee Refractive Management/Intervention Panel selected 26 articles that were considered to be of high or medium clinical relevance, and the panel methodologist rated each article according to the strength of evidence. Ten studies were rated as level I evidence, 5 studies were rated as level II evidence, and the remaining 11 studies were rated as level III evidence. The majority of the articles surveyed in this report support the role of MMC as an adjunctive treatment in surface ablation procedures. When MMC is applied in the appropriate concentration and confined to the central cornea, the incidence of post-surface ablation haze is decreased. Although a minority of studies that evaluated endothelial cell density (ECD) reported an MMC-related decrease in ECD, no clinical adverse outcomes were reported. Over the past 15 years, the use of MMC during surgery in surface ablation has become widespread. There is good evidence of the effectiveness of MMC when used intraoperatively as prophylaxis against haze in higher myopic ablations. Although there are reports of decreased endothelial counts after the administration of MMC during surgery, the clinical significance of this finding remains uncertain, because no adverse outcomes were reported with as much as 5 years of follow-up. Optimal dosage, effectiveness as prophylaxis in lower myopic and hyperopic ablations, and long-term safety, particularly in eyes with reduced corneal endothelial cell counts from prior intraocular surgery, have yet to be established. Copyright © 2015 American Academy of

  10. Photosensitivity and stress changes of Ge-free Bi-Al doped silica optical fibers under ArF excimer laser irradiation.

    Science.gov (United States)

    Ban, Christian; Limberger, Hans G; Mashinsky, Valery; Dianov, Evgeny

    2011-12-19

    The photosensitivity of germanium free Bi-Al-doped silica fibers with different bismuth concentrations was investigated using ArF excimer laser radiation at 193 nm and fiber grating formation. For the fiber with the highest bismuth concentration maximum refractive index changes of 2.2 × 10(-3) and 2.0 × 10(-4) were obtained for hydrogen loaded and unloaded fibers, respectively. Irradiation induced tensile stress changes were observed in the fiber core of H(2)-loaded and unloaded fibers. The results indicate a contribution of compaction to the total refractive index change in both cases.

  11. Surface modification of an Al2O3/SiO2 based ceramic treated with CO2, Nd:YAG, excimer and high power diode lasers for altered wettability characteristics

    OpenAIRE

    Lawrence, Jonathan; Li, Lin; Spencer, Julian T.

    1998-01-01

    Interaction of CO2, Nd:YAG, excimer and high power diode laser (HPDL) radiation with the surface of an Al2O3/SiO2 based ceramic was found to affect significant changes in the wettability characteristics of the material. It was observed that interaction with CO2, Nd:YAG and HPDL radiation reduced the enamel contact angle from 1180 to 310, 340 and 330 respectively. In contrast, interaction with excimer laser radiation resulted an increase in the contact angle to 1210. Such changes were identifi...

  12. Comparison of boron diffusion in silicon during shallow p{sup +}/n junction formation by non-melt excimer and green laser annealing

    Energy Technology Data Exchange (ETDEWEB)

    Aid, Siti Rahmah; Matsumoto, Satoru [Department of Electronics and Electrical Engineering, Keio University, 3-14-1 Hiyoshi, Kouhoku-ku, Yokohama, Kanagawa 223-8522 (Japan); Fuse, Genshu [SEN Corporation, SBS Tower 9F, 4-10-1 Yoga, Setagaya-ku, Tokyo 158-0097 (Japan); Sakuragi, Susumu [Sumitomo Heavy Industries Ltd., 19 Natsushima-cho, Yokosuka, Kanagawa 237-8555 (Japan)

    2011-12-15

    The combination of Ge pre-amorphization implantation, low-energy boron implantation, and non-melt laser annealing is a promising method for forming ultrashallow p{sup +}/n junctions in silicon. In this study, shallow p{sup +}/n junctions were formed by non-melt annealing implanted samples using a green laser (visible laser). The dopant diffusion, activation, and recrystallization of an amorphous silicon layer were compared with those obtained in our previous study in which non-melt annealing was performed using a KrF excimer laser (UV laser). The experimental results reveal that only slight diffusion of boron in the tail region occurred in green-laser-annealed samples. In contrast, remarkable boron diffusion occurred in KrF-laser-annealed samples for very short annealing times. Recrystallization of the amorphous silicon layer was slower in green-laser-annealed samples than in KrF-laser-annealed samples. We consider the penetration depth and the pulse duration are important factors that may affect boron diffusion. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  13. Femtosecond laser-assisted in situ keratomileusis multifocal ablation profile using a mini-monovision approach for presbyopic patients with hyperopia

    Directory of Open Access Journals (Sweden)

    Vastardis I

    2016-07-01

    Full Text Available Iraklis Vastardis,1 Brigitte Pajic-Eggspühler,1 Jörg Müller,1,2 Zeljka Cvejic,2 Bojan Pajic,1–4 1Swiss Eye Research Foundation, Orasis Eye Clinic, Aargau, Reinach, Switzerland; 2Faculty of Physics, University of Novi Sad, Novi Sad, Serbia; 3Department of Ophthalmology, Geneva University Hospitals, Geneva, Switzerland; 4Medical Faculty, Military Medical Academy, University of Defence, Belgrade, Serbia Purpose: To report the visual outcomes of the femtosecond laser-assisted multifocal aspheric corneal ablation profile using a mini-monovision approach and to evaluate if corneal multifocality was effective, and to report the relative benefits of this approach.Patients and methods: Bilateral femtosecond laser-assisted in situ keratomileusis using a multifocal aspheric corneal ablation profile was performed on 19 hyperopic patients (38 eyes. They were divided into two groups based on eye dominance: dominant eye (DE group targeting emmetropia and the nondominant eye (NDE group targeting -0.5 D slight myopia. The uncorrected distance visual acuity (UDVA, uncorrected intermediate visual acuity (UIVA, uncorrected near visual acuity (UNVA, and retreatment rates were reported from baseline to 6 months.Results: The UNVA, UIVA, and UDVA improved significantly in both groups (Kruskal–Wallis test, DE and NDE: P<0.00001, P<0.000005, and P=0.00001, respectively. Corrected distance visual acuity (CDVA baseline was better in both groups in comparison to UDVA at 6 months (Wilcoxon test, DE: P<0.001, 95% confidence interval (CI of the median 0.0–0.0 LogMAR and 0.1000–0.1218 LogMAR and NDE: P=0.010, 95% CI of the median 0.0–0.0 LogMAR and 0.00–0.10 LogMAR. There was a significant loss of lines between CDVA baseline and UDVA at 6 months in both groups (DE group: 68% of eyes lost one line or more; NDE group: 58% of eyes lost one line or more. The corrected near visual acuity baseline compared to UNVA at 6 months was not statistically important

  14. Some optical and electron microscope comparative studies of excimer laser-assisted and nonassisted molecular-beam epitaxically grown thin GaAs films on Si

    Science.gov (United States)

    Lao, Pudong; Tang, Wade C.; Rajkumar, K. C.; Guha, S.; Madhukar, A.; Liu, J. K.; Grunthaner, F. J.

    1990-01-01

    The quality of GaAs thin films grown via MBE under pulsed excimer laser irradiation on Si substrates is examined in both laser-irradiated and nonirradiated areas using Raman scattering, Rayleigh scattering, and by photoluminescence (PL), as a function of temperature, and by TEM. The temperature dependence of the PL and Raman peak positions indicates the presence of compressive stress in the thin GaAs films in both laser-irradiated and nonirradiated areas. This indicates incomplete homogeneous strain relaxation by dislocations at the growth temperature. The residual compressive strain at the growth temperature is large enough such that even with the introduction of tensile strain arising from the difference in thermal expansion coefficients of GaAs and Si, a compressive strain is still present at room temperature for these thin GaAs/Si films.

  15. Fabrication of functional fibronectin patterns by nanosecond excimer laser direct write for tissue engineering applications.

    Science.gov (United States)

    Grigorescu, S; Hindié, M; Axente, E; Carreiras, F; Anselme, K; Werckmann, J; Mihailescu, I N; Gallet, O

    2013-07-01

    Laser direct write techniques represent a prospective alternative for engineering a new generation of hybrid biomaterials via the creation of patterns consisting of biological proteins onto practically any type of substrate. In this paper we report on the characterization of fibronectin features obtained onto titanium substrates by UV nanosecond laser transfer. Fourier-transform infrared spectroscopy measurements evidenced no modification in the secondary structure of the post-transferred protein. The molecular weight of the transferred protein was identical to the initial fibronectin, no fragment bands being found in the transferred protein's Western blot migration profile. The presence of the cell-binding domain sequence and the mannose groups within the transferred molecules was revealed by anti-fibronectin monoclonal antibody immunolabelling and FITC-Concanavalin-A staining, respectively. The in vitro tests performed with MC3T3-E1 osteoblast-like cells and Swiss-3T3 fibroblasts showed that the cells' morphology and spreading were strongly influenced by the presence of the fibronectin spots.

  16. High-efficient discharge-pumped ArF (193 nm) excimer laser with a TPI thyratron as a high-voltage switch

    Science.gov (United States)

    Razhev, Alexander M.; Zhupikov, Andrey A.; Churkin, Dmitry S.

    2007-06-01

    The results of using the thyratron of the TPI series (pseudo spark gap) as a high-voltage switch in the excitation system of ArF (193 nm) excimer laser are presented. The excitation system of the LC-inverter type based on TPI 10k/20 thyratron in absence of any non-linear elements was developed. An experimental investigation of the energy and temporal parameters of the pumping and lasing for ArF laser on the He:Ar:F II mixture with excitation system developed was carried out. The comparative analysis of the ArF laser pumping and radiation parameters in dependence of the high-voltage switch type such as a standard spark gap RU-65, and thyratron TPI 10k/20 was performed. The output radiation energy for a laser with thyratron TPI 10k/20 was obtained to be of 1.4 times higher than that with standard spark gap RU-65 at the same pumping conditions. Such increase the output energy was shown to be achieving owing to higher level of the pumping intensity due to higher voltage on the discharge gap that occurs due to lower energy losses into TPI thyratron in comparison with the RU- 65 spark gap and leads to more efficient energy transfer from storage to discharge circuit. As a result for ArF laser with TPI thyratron in He:Ar:F II mixture the output radiation energy of 1.0 J with the total efficiency of 1.7% has been achieved. The advantages of using the TPI thyratron in the excitation system of the ArF excimer laser over spark gap are described.

  17. FEM for modelling 193 nm excimer laser treatment of SiO{sub 2}/Si/Si{sub (1-x)}Ge{sub x} heterostructures on SOI substrates

    Energy Technology Data Exchange (ETDEWEB)

    Conde, J.C.; Chiussi, S.; Gontad, F.; Gonzalez, P. [Dpto. Fisica Aplicada, E.T.S.I.I. University of Vigo, Campus Universitario, Rua Maxwell s/n, 36310 Vigo (Spain); Martin, E. [Dpto. de Mecanica, Maquinas, Motores Termicos y Fluidos, E.T.S.I.I. University of Vigo, Campus Universitario, Rua Maxwell s/n, 36310 Vigo (Spain)

    2011-03-15

    Research on epitaxial crystalline silicon (c-Si) and silicon-germanium (Si{sub 1-x}Ge{sub x}) alloys growth and annealing for microelectronic purposes, such as Micro- or Nano-Electro-Mechanical Systems (MEMS or NEMS) and Silicon-On-Nothing (SON) devices is continuously in progress. Laser assisted annealing techniques using commercial ArF Excimer Laser sources are based on ultra-rapid heating and cooling cycles induced by the 193 nm pulses of 20 ns, which are absorbed in the near surface region of the heterostructures. During and after the absorption of these laser pulses, complex physical processes appear that strongly depend on sample structure and applied laser pulse energy densities. The control of the experimental parameters is therefore a key task for obtaining high quality alloys. The Finite ElementsMethod (FEM) is a powerful tool for the optimization of such treatments, because it provides the spatial and temporal temperature fields that are produced by the laser pulses. In this work, we have used a FEM commercial software, to predict the temperatures gradients induced by ArF excimer laser over a wide energy densities range, 0.1<{phi}<0.4 J/cm{sup 2}, on different SiO{sub 2}/Si/Si{sub (1-x)}Ge{sub (x)} thin films deposited on SOI substrate. These numerical results allow us to predict the threshold energies needed to reach the melting point (MP) of the Si and SiGe alloy without oxidation of the thin films system. Therefore, it is possible to optimize the conditions to achieve high quality epitaxy films. (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  18. XeCl excimer laser-induced autofluorescence spectroscopy for human cerebral tumor diagnosis: preliminary study

    Science.gov (United States)

    Avrillier, Sigrid; Hor, Frederic; Desgeorges, Michel; Ettori, Dominique; Sitbon, Jean R.

    1993-09-01

    Three-hundred-eight nm laser-induced autofluorescence spectra of the normal human brain, astrocytoma grade IV and glioblastoma grade IV specimens, have been recorded in vitro two hours after surgical resection. Typical fluorescence spectra for normal (N) and malignant (M) tissue show 4 maxima at about 352, 362, 383, and 460 nm. These spectra are analyzed in detail. Subtle differences in normalized spectra of N and M tissues appear to be large enough for diagnosis. Several criteria such as maxima and minima absolute intensity and intensity ratios at typical wavelengths are computed and used to classify the tissue. This preliminary study shows that fluorescence spectroscopy with 308 nm UV excitation could be a valid technique for discriminating tumor types. However, it should be noted that these measurements are made in vitro. Living tissues may have different spectral characteristics, therefore future in vivo investigations must be performed.

  19. Low temperature high-mobility InZnO thin-film transistors fabricated by excimer laser annealing

    NARCIS (Netherlands)

    Fujii, M.; Ishikawa, Y.; Ishihara, R.; Van der Cingel, J.; Mofrad, M.R.T.; Horita, M.; Uraoka, Y.

    In this study, we successfully achieved a relatively high field-effect mobility of 37.7?cm2/Vs in an InZnO thin-film transistor (TFT) fabricated by excimer layer annealing (ELA). The ELA process allowed us to fabricate such a high-performance InZnO TFT at the substrate temperature less than 50?°C

  20. Low temperature high-mobility InZnO thin-film transistors fabricated by excimer laser annealing

    NARCIS (Netherlands)

    Fujii, M.; Ishikawa, Y.; Ishihara, R.; Van der Cingel, J.; Mofrad, M.R.T.; Horita, M.; Uraoka, Y.

    2013-01-01

    In this study, we successfully achieved a relatively high field-effect mobility of 37.7?cm2/Vs in an InZnO thin-film transistor (TFT) fabricated by excimer layer annealing (ELA). The ELA process allowed us to fabricate such a high-performance InZnO TFT at the substrate temperature less than 50?°C

  1. Effects of closed immersion filtered water flow velocity on the ablation threshold of bisphenol A polycarbonate during excimer laser machining

    Energy Technology Data Exchange (ETDEWEB)

    Dowding, Colin, E-mail: c.f.dowding@lboro.ac.uk [Wolfson School of Mechanical and Manufacturing Engineering, Loughborough University, Loughborough, Leicestershire, LE11 3TU (United Kingdom); Lawrence, Jonathan [Wolfson School of Mechanical and Manufacturing Engineering, Loughborough University, Loughborough, Leicestershire, LE11 3TU (United Kingdom)

    2010-04-01

    A closed flowing thick film filtered water immersion technique ensures a controlled geometry for both the optical interfaces of the flowing liquid film and allows repeatable control of flow-rate during machining. This has the action of preventing splashing, ensures repeatable machining conditions and allows control of liquid flow velocity. To investigate the impact of this technique on ablation threshold, bisphenol A polycarbonate samples have been machined using KrF excimer laser radiation passing through a medium of filtered water flowing at a number of flow velocities, that are controllable by modifying the liquid flow-rates. An average decrease in ablation threshold of 7.5% when using turbulent flow velocity regime closed thick film filtered water immersed ablation, compared to ablation using a similar beam in ambient air; however, the use of laminar flow velocities resulted in negligible differences between closed flowing thick film filtered water immersion and ambient air. Plotting the recorded threshold fluence achieved with varying flow velocity showed that an optimum flow velocity of 3.00 m/s existed which yielded a minimum ablation threshold of 112 mJ/cm{sup 2}. This is attributed to the distortion of the ablation plume effected by the flowing immersion fluid changing the ablation mechanism: at laminar flow velocities Bremsstrahlung attenuation decreases etch rate, at excessive flow velocities the plume is completely destroyed, removing the effect of plume etching. Laminar flow velocity regime ablation is limited by slow removal of debris causing a non-linear etch rate over 'n' pulses which is a result of debris produced by one pulse remaining suspended over the feature for the next pulse. The impact of closed thick film filtered water immersed ablation is dependant upon beam fluence: high fluence beams achieved greater etch efficiency at high flow velocities as the effect of Bremsstrahlung attenuation is removed by the action of the fluid on

  2. Agreement between clinical history method, Orbscan IIz, and Pentacam in estimating corneal power after myopic excimer laser surgery.

    Directory of Open Access Journals (Sweden)

    Kaevalin Lekhanont

    Full Text Available The purpose of this study was to investigate the agreement between the clinical history method (CHM, Orbscan IIz, and Pentacam in estimating corneal power after myopic excimer laser surgery. Fifty five patients who had myopic LASIK/PRK were recruited into this study. One eye of each patient was randomly selected by a computer-generated process. At 6 months after surgery, postoperative corneal power was calculated from the CHM, Orbscan IIz total optical power at the 3.0 and 4.0 mm zones, and Pentacam equivalent keratometric readings (EKRs at 3.0, 4.0, and 4.5 mm. Statistical analyses included multilevel models, Pearson's correlation test, and Bland-Altman plots. The Orbscan IIz 3.0-mm and 4.0 mm total optical power, and Pentacam 3.0-mm, 4.0-mm, and 4.5-mm EKR values had strong linear positive correlations with the CHM values (r = 0.90-0.94, P = <0.001, for all comparisons, Pearson's correlation. However, only Pentacam 3.0-mm EKR was not statistically different from CHM (P = 0.17, multilevel models. The mean 3.0- and 4.0-mm total optical powers of the Orbscan IIz were significantly flatter than the values derived from CHM, while the average EKRs of the Pentacam at 4.0 and 4.5 mm were significantly steeper. The mean Orbscan IIz 3.0-mm total optical power was the lowest keratometric reading compared to the other 5 values. Large 95% LoA was observed between each of these values, particularly EKRs, and those obtained with the CHM. The width of the 95% LoA was narrowest for Orbscan IIz 3.0-mm total optical power. In conclusion, the keratometric values extracted from these 3 methods were disparate, either because of a statistically significant difference in the mean values or moderate agreement between them. Therefore, they are not considered equivalent and cannot be used interchangeably.

  3. Formation of densely populated SiOx microtree-like structures on the Si (100) surface using excimer laser irradiation in air

    Science.gov (United States)

    Yang, De-Quan; Sacher, Edward; Meunier, Michel

    2004-10-01

    SiOx microforest-like structures have been produced on Si (100) surfaces by pulsed excimer laser irradiation in air. Scanning electron microscopic observations have indicated these structures, which are composed of aggregated nanoparticles, to be 1-5 μm in diameter and 10-20 μm high, and to have the appearance of trees. XPS analysis has shown them to be composed of a-SiOx (1laser irradiation, our microforest-like trees have many sharp nanoscale branches, which may require lower emission voltages in application such as field-emission sources in plasma displays.

  4. Fabrication of an integrated optical Mach-Zehnder interferometer based on refractive index modification of polymethylmethacrylate by krypton fluoride excimer laser radiation

    Science.gov (United States)

    Koerdt, Michael; Vollertsen, Frank

    2011-04-01

    It is known that deep ultraviolet (UV) radiation induces a refractive index increase in the surface layer of polymethylmethacrylate (PMMA) samples. This effect can be used for the fabrication of integrated optical waveguides. PMMA is of considerable interest for bio and chemical sensing applications because it is biocompatible and can be micromachined by several methods, e.g. structuring by photolithography, ablation and hot embossing. In the presented work direct UV irradiation of a common PMMA substrate by a krypton fluoride excimer laser beam through a contact mask has been used to write integrated optical Mach-Zehnder interferometers (MZI). MZI are used as sensitive bio and chemical sensors. The aim was to determine contact mask design and laser irradiation parameters for fabricating single-mode MZI for the infrared region from 1.30 μm to 1.62 μm. Straight and curved waveguides have been generated and characterized to determine the optical losses. The generation of channel waveguide structures has been optimized by a two step irradiation process to minimize the lithographic writing time and optical loss. By flood exposure to UV laser radiation in the first step the optical absorption of PMMA can be increased in the irradiated region. The required refractive index profile is then achieved with a second lithographic irradiation. The spectral behaviour of an unbalanced, integrated optical MZI fabricated by this excimer laser based contact mask method is shown for the first time. Further the optical intensity at the output port of a MZI has been measured while the optical path length difference was tuned by creating a temperature difference between the two arms of the MZI.

  5. Fabrication of an integrated optical Mach-Zehnder interferometer based on refractive index modification of polymethylmethacrylate by krypton fluoride excimer laser radiation

    Energy Technology Data Exchange (ETDEWEB)

    Koerdt, Michael, E-mail: koerdt@bias.de [BIAS - Bremer Institut fuer angewandte Strahltechnik GmbH, Klagenfurter Strasse 2, D-28359 Bremen (Germany); Vollertsen, Frank [BIAS - Bremer Institut fuer angewandte Strahltechnik GmbH, Klagenfurter Strasse 2, D-28359 Bremen (Germany)

    2011-04-01

    It is known that deep ultraviolet (UV) radiation induces a refractive index increase in the surface layer of polymethylmethacrylate (PMMA) samples. This effect can be used for the fabrication of integrated optical waveguides. PMMA is of considerable interest for bio and chemical sensing applications because it is biocompatible and can be micromachined by several methods, e.g. structuring by photolithography, ablation and hot embossing. In the presented work direct UV irradiation of a common PMMA substrate by a krypton fluoride excimer laser beam through a contact mask has been used to write integrated optical Mach-Zehnder interferometers (MZI). MZI are used as sensitive bio and chemical sensors. The aim was to determine contact mask design and laser irradiation parameters for fabricating single-mode MZI for the infrared region from 1.30 {mu}m to 1.62 {mu}m. Straight and curved waveguides have been generated and characterized to determine the optical losses. The generation of channel waveguide structures has been optimized by a two step irradiation process to minimize the lithographic writing time and optical loss. By flood exposure to UV laser radiation in the first step the optical absorption of PMMA can be increased in the irradiated region. The required refractive index profile is then achieved with a second lithographic irradiation. The spectral behaviour of an unbalanced, integrated optical MZI fabricated by this excimer laser based contact mask method is shown for the first time. Further the optical intensity at the output port of a MZI has been measured while the optical path length difference was tuned by creating a temperature difference between the two arms of the MZI.

  6. Excimer Laser Research

    Science.gov (United States)

    1976-10-01

    ORGANIZATION N ATTETSTTF»UUHLJJ* Avco Everett Research Laboratory, Inc. 2385 Revere Beach Parkway Everett, Massachusetts 02149 REPORT...apparently enhanced by a large reactive c -oss section for producing excited species by chemica ’ reactions of the type Xe« I F,-XeF* • F. (1

  7. The applicability of the Sedov - Taylor scaling during material removal of metals and oxide layers with pulsed ? and excimer laser radiation

    Science.gov (United States)

    Aden, M.; Kreutz, E. W.; Schlüter, H.; Wissenbach, K.

    1997-03-01

    For the removal of material with pulsed laser radiation the distance travelled by the shock or blast wave and the amount of energy released in the plasma state due to the absorption of laser radiation are determined experimentally and theoretically. The distance travelled by the blast wave is detected by schlieren photography, the released energy by monitoring the transmitted laser radiation during the removal process. The theoretical evaluation is performed by numerical simulation using a model incorporating the laser-induced vaporization process and the dynamics of the plasma state. The results obtained from the experiments and the model are compared with that of the Sedov - Taylor scaling. The removal of the oxide layer from austenitic steel is investigated with 0022-3727/30/6/011/img8 laser radiation produced by a TEA and a high-power 0022-3727/30/6/011/img8 laser device. For the TEA laser with fluences of 5 and 10 J 0022-3727/30/6/011/img10 50 - 80% of the pulse energy is released into the plasma state and the Sedov - Taylor scaling describes the distance travelled by the blast wave in agreement with data from the experiments and the simulation. For the high-power 0022-3727/30/6/011/img8 laser with a fluence of 50 J 0022-3727/30/6/011/img10, 6% of the pulse energy is released into the plasma state and the Sedov - Taylor scaling does not describe the data of the simulation. The process of removal of copper and aluminium material is simulated for excimer laser radiation with fluences of 15 and 30 J 0022-3727/30/6/011/img10. For copper 15 - 30% of the pulse energy is released into the plasma state and the Sedov - Taylor scaling is applicable. For aluminium, less than 2% of the pulse energy is released into the plasma state and the Sedov - Taylor scaling is only applicable for the higher fluence.

  8. Assessment of expressions of heat shock protein (HSP 72) and apoptosis after ArF excimer laser ablation of the cornea.

    Science.gov (United States)

    Ishihara, Miya; Sato, Masato; Sato, Shunichi; Arai, Tsunenori; Obara, Minoru; Kikuchi, Makoto

    2004-01-01

    We immunohistochemically studied expressions of inducible heat shock protein 70 (HSP 72) and apoptosis of corneas ablated with an ArF excimer laser. The temperature of corneal surfaces and laser-induced optical emission spectra were measured in real time as direct physical parameters related to the ablation mechanism. To the best of the authors' knowledge, there have been no experimental studies regarding the influence of physical parameters directly related to the ablation mechanism on corneal reactions at the cell level after laser ablation. The expression of HSP 72 was mainly localized in the regenerative epithelium, which was confirmed to be caused by laser ablation. The HSP 72 positive cell ratios had a correlation with thermal dose, which was derived from the measured time courses of temperature. Expressions of both HSP 72 and apoptosis depended on the thermal dose and elapsed time after ablation. HSP 72 and apoptosis could be seen up to a few hundred micrometers into the stroma, only at a fluence with an optical breakdown emission. This could have been caused by shock waves induced by the optical breakdown. (c) 2004 Society of Photo-Optical Instrumentation Engineers.

  9. EFFECT OF OPTICAL FIBER HYDROGEN LOADING ON THE INSCRIPTION EFFICIENCY OF CHIRPED BRAGG GRATINGS BY MEANS OF KrF EXCIMER LASER RADIATION

    Directory of Open Access Journals (Sweden)

    Sergey V. Varzhel

    2016-11-01

    Full Text Available Subject of Research.We present comparative results of the chirped Bragg gratings inscription efficiency in optical fiber of domestic production with and without low-temperature hydrogen loading. Method. Chirped fiber Bragg gratings inscription was made by the Talbot interferometer with chirped phase mask having a chirp rate of 2.3 nm/cm used for the laser beam amplitude separation. The excimer laser system Coherent COMPexPro 150T, working with the gas mixture KrF (248 nm, was used as the radiation source. In order to increase the UV photosensitivity, the optical fiber was placed in a chamber with hydrogen under a pressure of 10 MPa and kept there for 14 days at 40 °C. Main Results. The usage of the chirped phase mask in a Talbot interferometer scheme has made it possible to get a full width at half-maximum of the fiber Bragg grating reflection spectrum of 3.5 nm with induced diffraction structure length of 5 mm. By preliminary hydrogen loading of optical fiber the broad reflection spectrum fiber Bragg gratings with a reflectivity close to 100% has been inscribed. Practical Relevance. The resulting chirped fiber Bragg gratings can be used as dispersion compensators in optical fiber communications, as well as the reflective elements of distributed fiber-optic phase interferometric sensors.

  10. Experience in using the excimer laser-assisted nonocclusive anastomosis nonocclusive bypass technique for high-flow revascularization: Mannheim-Helsinki series of 64 patients.

    Science.gov (United States)

    Vajkoczy, Peter; Korja, Miikka; Czabanka, Marcus; Schneider, Ulf C; Reinert, Michael; Lehecka, Martin; Schmiedek, Peter; Hernesniemi, Juha; Kivipelto, Leena

    2012-01-01

    The excimer laser-assisted nonocclusive anastomosis (ELANA) technique enables large-caliber bypass revascularization without temporary occlusion of the parent artery. To present the surgical experience of 2 bypass centers using ELANA in the treatment of complex intracranial lesions. Between July 2002 and December 2007, 64 consecutive patients (37 in Germany and 27 in Finland) were selected for high-flow bypass surgery with ELANA. Modified Rankin Scale, a bypass success rate, and the success rate of the laser arteriotomy were assessed. In 66 surgeries for 64 intent-to-treat patients, 58 ELANA procedures were completed successfully. A favorable outcome (postoperative modified Rankin Scale score less than or equal to preoperative modified Rankin Scale) at 3 months was achieved in 43 of 56 patients (77%) with anterior circulation lesions (37 of the 43 patients had aneurysms, 4 had ischemia, and 2 received a bypass before tumor removal) and only in 2 of 8 patients (25%) with posterior circulation aneurysms. Perioperative (< 7 days) mortality for anterior and posterior circulation aneurysms was 6% and 50%, respectively. At the 3-month follow-up, 12% and 63% of patients with anterior and posterior circulation aneurysms, respectively, were dead. The success rate of the laser arteriotomy was 70%. Another 14% were retrieved manually after a nearly complete laser arteriotomy. The ELANA procedure requires a meticulous and careful operative technique. Morbidity and especially mortality rates, usually unrelated to ELANA, are comparable to those of contemporary series of conventional high-flow revascularization operations. This underscores the overall complexity of treating neurovascular pathologies by high-flow bypasses.

  11. Surface 3D Micro Free Forms: Multifunctional Microstructured Mesoporous α-Alumina by in Situ Slip Casting Using Excimer Laser Ablated Polycarbonate Molds.

    Science.gov (United States)

    Rowthu, Sriharitha; Böhlen, Karl; Bowen, Paul; Hoffmann, Patrik

    2015-11-11

    Ceramic surface microstructuring is a rapidly growing field with a variety of applications in tribology, wetting, biology, and so on. However, there are limitations to large-area microstructuring and fabrication of three-dimensional (3D) micro free forms. Here, we present a route to obtain intricate surface structures through in situ slip casting using polydimethylsiloxane (PDMS) negative molds which are replicated from excimer laser ablated polycarbonate (PC) master molds. PC sheets are ablated with a nanosecond KrF (λ = 248 nm) excimer laser mask projection system to obtain micron-scale 3D surface features over a large area of up to 3 m(2). Complex surface structures that include 3D free forms such as 3D topography of Switzerland, shallow structures such as diffractive optical elements (60 nm step) and conical micropillars have been obtained. The samples are defect-free produced with thicknesses of up to 10 mm and 120 mm diameter. The drying process of the slip cast alumina slurry takes place as a one-dimensional process, through surface evaporation and water permeation through the PDMS membrane. This allows homogeneous one-dimensional shrinkage during the drying process, independent of the sample's lateral dimensions. A linear mass diffusion model has been proposed to predict and explain the drying process of these ceramic colloidal suspensions. The calculated drying time is linearly proportional to the height of the slurry and the thickness of the negatively structured PDMS and is validated by the experimental results. An experimentally observed optimum Sylgard PDMS thickness range of ∼400 μm to 1 mm has achieved the best quality microstructured green compacts. Further, the model predicts that the drying time is independent of the microstructured areas and was validated using experimental observations carried out with microstructured areas of 300 mm(2), 1200 mm(2), and 120 cm(2). Therefore, in principle, the structures can be further replicated in areas up

  12. High-performance p-channel thin-film transistors with lightly doped n-type excimer-laser-crystallized germanium films

    Science.gov (United States)

    Liao, Chan-Yu; Huang, Ching-Yu; Huang, Ming-Hui; Huang, Wen-Hsien; Shen, Chang-Hong; Shieh, Jia-Min; Cheng, Huang-Chung

    2017-06-01

    High-performance polycrystalline-germanium (poly-Ge) thin-film transistors (TFTs) fabricated with lightly doped Ge thin films by excimer laser crystallization (ELC) and counter doping (CD) have been demonstrated. High-quality n-type Ge thin films with a grain size as large as 1 µm were fabricated by ELC in the super lateral-growth regime and CD at a dose of 1 × 1013 cm-2 or higher. Consequently, a superior field-effect mobility of 271 cm2 V-1 s-1 and a high on/off current ratio of 2.7 × 103 have been obtained for p-channel Ge TFTs with the channel width and length of both 0.5 µm fabricated by ELC at 300 mJ/cm2 and CD at a dose of 1 × 1013 cm-2. The effects of ELC conditions and CD dose on the electrical characteristics of p-channel Ge TFTs were also investigated.

  13. [Subjective visual perception after laser treatment of myopia on two types of lasers].

    Science.gov (United States)

    Kyprianou, G; Machácková, M; Feuermannová, A; Rozsíval, P; Langrová, H

    2010-11-01

    Comparison of subjective evaluation of patients with low and moderate myopia undergoing photorefractive keratectomy (PRK) and Laser in Situ Keratomileusis (LASIK) on two types of excimer lasers: Schwind Esiris and Schwind Amaris. Patients were divided into two groups according to the type of laser that was used. Group A comprised of 23 patients (14 females, 9 males) of average age 33.1 years (range 21-51 years), with an average spherical equivalent before operation of -3.5D. Using the excimer laser Esiris (Schwind, Germany), 10 patients had undergone PRK and 13 LASIK. Group B comprised of 32 patients (21 females, 11 males), of average age 31.9 years (range 22-48 years). Median spherical equivalent before operation was -3.05D. With the excimer laser Amaris (Schwind, Germany) 17 patients had undergone PRK and 15 LASIK. For the subjective evaluation we set up a questioner consisting of 21 questions that were aimed on the quality of vision under various illumination types and intensities, vision under various distances, activities and also questions concerning superficial sensitivity of the anterior segment of the eye. We detected a 100% satisfaction one year after refractive laser treatment with both laser types. Statistical improvement was evident by one month after treatment in both patient groups and upto 12 months it progressively increased. Statistically significant differences were noted one month after treatment, where patients in group B were more satisfied in questions concerning quality of vision, distance vision, while watching TV and driving during daytime and during the night. During further follow-up, results were comparable between both groups. Temporary patient satisfaction treated with laser Amaris is apparently due to the result of a more sparing treatment and thus fewer changes in the corneal stroma.

  14. Surface analysis of the selective excimer laser patterning of a thin PEDOT:PSS film on flexible polymer films

    Science.gov (United States)

    Schaubroeck, David; De Smet, Jelle; Willems, Wouter; Cools, Pieter; De Geyter, Nathalie; Morent, Rino; De Smet, Herbert; Van Steenbeerge, Geert

    2016-07-01

    Fast patterning of highly conductive polymers like PEDOT:PSS (poly (3,4-ethylene dioxythiophene): polystyrene sulfonate) with lasers can contribute to the development of industrial production of liquid crystal displays on polymer foils. In this article, the selective UV laser patterning of a PEDOT:PSS film on flexible polymer films is investigated. Based on their optical properties, three polymer films are investigated: polyethylene terephthalate (PET), polymethyl methacrylate (PMMA) and cellulose triacetate (TAC). Ablation parameters for a 110 nm PEDOT:PSS film on these polymer films are optimized. A detailed study of the crater depth, topography and surface composition are provided using optical profilometry, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), respectively. The electrical insulation of the lines is measured and correlated to the crater analyses for different laser settings. Finally, potential ablation parameters for each of the polymer films are derived.

  15. Review of the biocompatibility and blood compatibility properties of polyethersulfone film modified by the excimer and CO2 lasers

    Science.gov (United States)

    Pazokian, H.; Jelvani, S.; Mollabashi, M.; Barzin, J.

    2014-06-01

    In this paper the biocompatibility and blood compatibility changes of polyethersulfone (PES) films following laser irradiation at four different wavelengths of ArF (193 nm), KrF (248 nm), XeCl (308 nm) and CO2 (9.58 µm) lasers are studied. The surface behaviors in contact with platelets and fibroblasts cells are examined and the best irradiation parameters to improve the surface biocompatibility and blood compatibility were found. The biological modifications on the surface were explained by alteration of the surface morphology and chemistry following the irradiation. The results show that a KrF laser is the best choice for treatment of PES film in the biological applications.

  16. FEM numerical analysis of excimer laser induced modification in alternating multi-layers of amorphous and nano-crystalline silicon films

    Energy Technology Data Exchange (ETDEWEB)

    Conde, J.C., E-mail: jconde@uvigo.es [Dpto. Fisica Aplicada, Universidade de Vigo, Rua Maxwell s/n, Campus Universitario Lagoas Marcosende, Vigo (Spain); Martin, E. [Dpto. Mecanica, Maquinas, Motores Termicos y Fluidos, Universidade de Vigo, Rua Maxwell s/n, Campus Universitario Lagoas Marcosende, Vigo (Spain); Stefanov, S. [Dpto. Fisica Aplicada, Universidade de Vigo, Rua Maxwell s/n, Campus Universitario Lagoas Marcosende, Vigo (Spain); Alpuim, P. [Departamento de Fisica, Universidade do Minho, 4800-058 Guimaraes (Portugal); Chiussi, S. [Dpto. Fisica Aplicada, Universidade de Vigo, Rua Maxwell s/n, Campus Universitario Lagoas Marcosende, Vigo (Spain)

    2012-09-15

    Highlights: Black-Right-Pointing-Pointer nc-Si:H is a material with growing importance for a large-area of nano-electronic, photovoltaic or biomedical devices. Black-Right-Pointing-Pointer UV-ELA technique causes a rapid heating that provokes the H{sub 2} desorption from the Si surface and bulk material. Black-Right-Pointing-Pointer Next, diffusion of P doped nc-Si films and eventually, for high energy densities would be possible to reach the melting point. Black-Right-Pointing-Pointer These multilayer structures consisting of thin alternating a-Si:H(10 nm) and n-doped nc-Si:H(60 nm) films deposited on SiO{sub 2}. Black-Right-Pointing-Pointer To optimize parameters involved in this processing, FEM numerical analysis of multilayer structures have been performed. Black-Right-Pointing-Pointer The numerical results are compared with exhaustive characterization of the experimental results. - Abstract: UV excimer laser annealing (UV-ELA) is an alternative annealing process that, during the last few years, has gained enormous importance for the CMOS nano-electronic technologies, with the ability to provide films and alloys with electrical and optical properties to fit the desired device performance. The UV-ELA of amorphous (a-) and/or doped nano-crystalline (nc-) silicon films is based on the rapid (nanoseconds) formation of temperature profiles caused by laser radiation that is absorbed in the material and lead to crystallisation, diffusion in solid or even in liquid phase. To achieve the desired temperature profiles and to optimize the parameters involved in the processing of hydrogenated nanocrystalline silicon (nc-Si:H) films with the UV-ELA, a numerical analysis by finite element method (FEM) of a multilayer structure has been performed. The multilayer structures, consisting of thin alternating a-Si:H(10 nm) and n-doped nc-Si:H(60 nm) layers, deposited on a glass substrate, has also been experimentally analyzed. Temperature profiles caused by 193 nm radiation with 25

  17. Surface analysis of the selective excimer laser patterning of a thin PEDOT:PSS film on flexible polymer films

    Energy Technology Data Exchange (ETDEWEB)

    Schaubroeck, David, E-mail: David.Schaubroeck@elis.ugent.be [Center for Microsystems Technology (CMST), imec and Ghent University, Technologiepark 15, B-9052 Ghent (Belgium); De Smet, Jelle; Willems, Wouter [Center for Microsystems Technology (CMST), imec and Ghent University, Technologiepark 15, B-9052 Ghent (Belgium); Cools, Pieter; De Geyter, Nathalie; Morent, Rino [Research Unit Plasma Technology (RUPT), Department of Applied Physics, Faculty of Engineering, Ghent University, Sint-Pietersnieuwstraat 41, B-9000 Ghent (Belgium); De Smet, Herbert; Van Steenbeerge, Geert [Center for Microsystems Technology (CMST), imec and Ghent University, Technologiepark 15, B-9052 Ghent (Belgium)

    2016-07-15

    Highlights: • Laser patterning of thin film PEDOT:PSS on polymer foils is characterized in great detail. • PEDOT:PSS does not need to be fully removed to create electrically insulating patterns. • The underlying polymer foil influences the ablation behavior. - Abstract: Fast patterning of highly conductive polymers like PEDOT:PSS (poly (3,4-ethylene dioxythiophene): polystyrene sulfonate) with lasers can contribute to the development of industrial production of liquid crystal displays on polymer foils. In this article, the selective UV laser patterning of a PEDOT:PSS film on flexible polymer films is investigated. Based on their optical properties, three polymer films are investigated: polyethylene terephthalate (PET), polymethyl methacrylate (PMMA) and cellulose triacetate (TAC). Ablation parameters for a 110 nm PEDOT:PSS film on these polymer films are optimized. A detailed study of the crater depth, topography and surface composition are provided using optical profilometry, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), respectively. The electrical insulation of the lines is measured and correlated to the crater analyses for different laser settings. Finally, potential ablation parameters for each of the polymer films are derived.

  18. Monovisión con láser de excímeros en pacientes présbitas Monovision with Excimer laser surgery in presbyopic patients

    Directory of Open Access Journals (Sweden)

    Patricia Andújar Coba

    2010-01-01

    previstos que caracterizan a la cirugía con láser de excímeros.OBJECTIVES: To describe the refractive results achieved with Excimer laser surgery in presbyopic patients, both hyperopic and myopic, with monovision. METHODS: A prospective, longitudinal and descriptive study was performed on 60 presbyopic patients, 18 myopic and 42 hyperopic, who underwent Excimer laser surgery to correct presbyopia based on the monovision method at the Corneal and Refractive Surgery Service of «Ramón Pando Ferrer» Cuban Institute of Ophthalmology from February 2009 to February 2010. The variables used were pre- and post-operative visual acuity with correction, visual acuity without binocular correction, both near and distant, and spheral equivalents. For presenting this information, the mean and standard deviation were used for all variables. RESULTS: In the preoperative phase, it was observed that average visual acuity improved from 0,1 and 0,3 for myopic and hyperopic patients without correction, to 0,94 and 0,97 binocular visual acuity without correction for the same groups in the postoperative phase, thus correcting their average spherical equivalent of 4,63 D and +2,21 D respectively. Average near visual acuity for both groups was Jeager (J 1 - 2 and average spheral equivalents reached for distant vision were 0,02 ± 0, 27 D for myopic and +0.09 ± 0,34 D for hyperopic patients. For near vision, i.e. in the non- dominant eye, the spheral equivalent values were 1.7 ± 0,22 D for myopic and 1.4 ± 0,38 D for hyperopic patients. CONCLUSIONS: After surgery both myopic and hyperopic patients experienced improvement in their visual acuity without correction for distant as well as for near vision. Spheral equivalents were widely modified in both groups for the dominant and non-dominant eyes, in order to facilitate the final visual result in both distances with the foreseen precision in the visual results that characterizes the Excimer laser surgery.

  19. Preparation of periodic surface structures on doped poly(methyl metacrylate) films by irradiation with KrF excimer laser

    Science.gov (United States)

    Kalachyova, Yevgeniya; Lyutakov, Oleksiy; Slepicka, Petr; Elashnikov, Roman; Svorcik, Vaclav

    2014-10-01

    In this work, we describe laser modification of poly(methyl methacrylate) films doped with Fast Red ITR, followed by dopant exclusion from the bulk polymer. By this procedure, the polymer can be modified under extremely mild conditions. Creation of surface ordered structure was observed already after application of 15 pulses and 12 mJ cm-2 fluence. Formation of grating begins in the hottest places and tends to form concentric semi-circles around them. The mechanism of surface ordered structure formation is attributed to polymer ablation, which is more pronounced in the place of higher light intensity. The smoothness of the underlying substrate plays a key role in the quality of surface ordered structure. Most regular grating structures were obtained on polymer films deposited on atomically `flat' Si substrates. After laser patterning, the dopant was removed from the polymer by soaking the film in methanol.

  20. Low temperature sputter-deposited ZnO films with enhanced Hall mobility using excimer laser post-processing

    Science.gov (United States)

    Tsakonas, C.; Kuznetsov, V. L.; Cranton, W. M.; Kalfagiannis, N.; Abusabee, K. M.; Koutsogeorgis, D. C.; Abeywickrama, N.; Edwards, P. P.

    2017-12-01

    We report the low temperature (T  ZnO thin films (~140 nm) with Hall mobility of up to 17.3 cm2 V‑1 s‑1 making them suitable for thin film transistor (TFT) applications. The films were deposited by rf magnetron sputtering at T  V‑1 s‑1 at a carrier density of 2.3  ×  1018 cm‑3 was measured from a 1 GΩ as deposited and aged film after the laser treatment. We suggest that the aging of non-processed films reduces structural defects mainly at grain boundaries by air species chemisorption, with concomitant increase in thermal conductivity so that laser processing can have an enhancing effect. Such a processing combination can act synergistically and produce suitable active layers for TFT applications with low temperature processing requirements.

  1. Evaluating the interaction of 308-nm xenon chloride excimer laser with human dentin and enamel hard tissues

    Directory of Open Access Journals (Sweden)

    Mahshid Yaghmaeian-Mahabadi

    2017-11-01

    Full Text Available Background: The pulsed output of the 308 nm XeCl laser and its photoablation action rather than photothermal action offers the ability to remove dental hard tissues with minimal generation of heat in the tissue. Materials and Methods: A total of 20 human molar teeth (ten teeth used as enamel samples and ten teeth used as dentin samples after removing the enamel tissue from their crowns were irradiated by the laser. The crown of each sample was regarded as a cube which its lateral sides were exposed in 2Hz frequency without water cooling. Also, 18 holes for all enamel samples and 18 holes for all dentin samples were obtained. Three different amounts of energy were selected as a variable factor with 6 different numbers of pulses in each energy. The images of these holes were prepared by optic and computer combining, and the amounts of the ablation depth and effective ablation area were calculated using the MATLAB software. Results: The amounts of ablation depth were increased with increasing the number of pulses for both enamel and dentin tissues. The amounts of ablation depth were also increased with increasing the amounts of energy for both enamel and dentin tissues. The greater amounts of ablation depth and effective ablation area were observed in the dentin tissue rather than the enamel tissue. The borders of created holes were reported sharp and clear. Conclusion: The application of the XeCl laser for hard tissue removal and cavity preparation can be possible after some certain modifications.

  2. Suppressed intermixing in InAlGaAs/AlGaAs/GaAs and AlGaAs/GaAs quantum well heterostructures irradiated with a KrF excimer laser

    Energy Technology Data Exchange (ETDEWEB)

    Genest, J.; Dubowski, J.J.; Aimez, V. [Universite de Sherbrooke, Centre de recherche en Nanofabrication et Nanocaracteriasation (CRN2), Departement de Genie Electrique et Genie Informatique, Sherbrooke, Quebec (Canada)

    2007-11-15

    The influence of gallium arsenide surface modification induced by irradiation with a KrF excimer laser on the magnitude of the quantum well (QW) intermixing effect has been investigated in InAlGaAs/AlGaAs/GaAs QW heterostructures. The irradiation in an air environment with laser pulses of fluences between 60 and 100 mJ/cm{sup 2} has resulted in the formation of a gallium oxide-rich film at the surface. Following the annealing at 900 C, up to 35 nm suppression of the band gap blue shift was observed in all the laser irradiated samples when compared to the non-irradiated samples. The origin of suppression has been discussed in terms of stress controlled diffusion. (orig.)

  3. Controlling the parameters of YBa2Cu3O(7-delta) high-temperature superconductors through excimer laser irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Dovgii, IA.O.; Kityk, I.V.; Lutsiv, R.V.; Malinich, S.Z.; Nosan, A.V.

    1991-02-01

    Single crystals (2x3 sq mm) of YBa2Cu3O(7{minus}{delta}) high-temperature superconductors were irradiated by an XeCl laser pumped by a gas discharge with a voltage of 35 kW and a frequency of 5 Hz. The formation of the superconducting phase was observed at oxygen pressures of 4-8 kbar. With an increase in oxygen pressure to 20 kbar, the transition temperature increased to 90 K. A possible mechanism of the observed phenomenon is examined.

  4. Controlling the parameters of YBa2Cu3O(7-delta) high-temperature superconductors through excimer laser irradiation

    Science.gov (United States)

    Dovgii, Ia. O.; Kityk, I. V.; Lutsiv, R. V.; Malinich, S. Z.; Nosan, A. V.

    1991-02-01

    Single crystals (2x3 sq mm) of YBa2Cu3O(7-delta) high-temperature superconductors were irradiated by an XeCl laser pumped by a gas discharge with a voltage of 35 kW and a frequency of 5 Hz. The formation of the superconducting phase was observed at oxygen pressures of 4-8 kbar. With an increase in oxygen pressure to 20 kbar, the transition temperature increased to 90 K. A possible mechanism of the observed phenomenon is examined.

  5. Four-year to seven-year outcomes of advanced surface ablation with excimer laser for high myopia

    DEFF Research Database (Denmark)

    Hansen, Rasmus Søgaard; Lyhne, Niels; Grauslund, Jakob

    2015-01-01

    Purpose: To evaluate and compare long-term outcomes ofafter photorefractive keratectomy with cooling (cPRK) and laser-assisted subepithelial keratectomy (LASEK) for high myopia. Methods: Retrospective single-masked follow-up study of patients treated for myopia between 2007 and 2009 with c...... ±1.0 D of intended refraction. Finally, 100% of cPRK patients and 92% of LASEK patients (P=0.87) were satisfied or very satisfied with the surgery at final follow-up. Conclusion: cPRK and LASEK seemed safe and with high patient satisfaction 4 to 7 years after surgery for high myopia. However, c...

  6. The correlation between the laser energy density and the properties of diamond-like carbon films with Nd:YAG (355 nm) excimer laser

    CERN Document Server

    Jung, H S; Pang, S S; Lee, S Y

    1998-01-01

    Diamond-like carbon (DLC) films were deposited using pulsed laser ablation of graphite target. The deposition process was performed with the change of laser energy density from 8 to 17 J/cm sup 2. collected from analytical results, laser energy density is seen to play an important role in the formation of sp sup 3 carbon bondings in films. Also, the optimal deposition condition for DLC films was proposed and correlated with the laser energy density.

  7. Development and numerical solution of a mechanistic model for corneal tissue ablation with the 193 nm argon fluoride excimer laser

    Science.gov (United States)

    Fisher, Brian T.; Hahn, David W.

    2007-02-01

    We detail the development and implementation of a global ablation model that incorporates a dynamically changing tissue absorption coefficient. Detailed spectroscopic measurements rule out plasma-shielding effects during the laser-tissue interaction and thereby support a photochemical mechanism. The model predicts ablation rate behavior that agrees well with a variety of experimental ablation rate data and that substantially deviates from a static Beer-Lambert model. The dynamic model predicts an enhancement in the tissue absorption coefficient of about 25%-50% as compared with the initial, static value. In addition, the model predicts an increase in the tissue ablation rate as corneal hydration increases, which may provide additional insight into variations in refractive surgery outcome.

  8. LASER PHYSICS: Formation of XeCl excimer molecules as a result of mixing of gas streams excited by a continuous discharge

    Science.gov (United States)

    Mikhkel'soo, V. T.; Treshchalov, A. B.; Peét, V. É.; Yalviste, É. Kh; Belokon', A. A.; Braĭnin, B. I.; Khritov, K. M.

    1987-07-01

    A longitudinal continuous discharge in two independent supersonic gas streams, which were subsequently mixed, was used for nonequilibrium electronic excitation of components undergoing reactions and emitting chemiluminescence. Formation of XeCl excimer molecules as a result of mixing of excited He:Xe = 95:5 and He:HCl(Cl2) = 99:1 streams was deduced from the XeCl* fluorescence spectra (B→X and C→A bands). The steady-state concentration of the XeCl molecules in B and C states determined in the mixing region was ~1010 cm-3 when the pump power was 50 W, so that the efficiency of conversion of the input electrical energy into the excimer fluorescence was ~1%.

  9. Seven year follow-up after advanced surface ablation with excimer laser for treatment of myopia: Long-term outcomes of cooling PRK and LASEK

    DEFF Research Database (Denmark)

    Hansen, Rasmus Søgaard; Lyhne, Niels; Grauslund, Jakob

    , Odense University Hospital. Inclusion criteria: Age 20-50 years at time of surgery, pre-operative CDVA ≤ 0.10 (logMAR) and no other ocular conditions than myopia with or without astigmatism of maximum 3 D. Exclusion criteria: Pregnancy and eyes having undergone re-treatment. A MEL80 flying-spot excimer......, corneal densitometry and patient satisfaction, although the long-term predictability of cPRK seemed better. Financial Disclosures: None...

  10. ArF excimer laser modulation of TNF-alpha and gelatinase B in NIH 3T3 cells; Modulation de l`expression du TNF-alpha et de la gelatinase B, apres irradiation de fibroblastes NIH 3T3 par un laser a excimeres a 193 NM

    Energy Technology Data Exchange (ETDEWEB)

    Naudy-Vives, C.; Courant, D.; Perot, J.C.; Garcia, J.; Fretier, P.; Court, L.; Dormont, D.

    1995-12-31

    The effects on TNF-alpha and gelatinase B activity in mammalian cells induced by 193 nm argon fluoride excimer laser have been investigated. The data show that a secretion of 92 kDa type IV collagenase and TNF-alpha were increased in cell culture supernatants. Moreover, the 193 nm laser radiation produces a decrease of cell proliferation and an increase of cell activation 8 hours after irradiation. The total protein amount increases with the delivered dose. Same, but less effects were obtained after exposure to a conventional UV lamp at 254 nm. (author). 8 refs.

  11. A prospective, randomized, fellow eye comparison of WaveLight® Allegretto Wave® Eye-Q versus VISX CustomVue™ STAR S4 IR™ in laser in situ keratomileusis (LASIK: analysis of visual outcomes and higher order aberrations

    Directory of Open Access Journals (Sweden)

    Moshirfar M

    2011-09-01

    Full Text Available Majid Moshirfar1, Brent S Betts2, Daniel S Churgin3, Maylon Hsu1, Marcus Neuffer1, Shameema Sikder4, Dane Church5, Mark D Mifflin11John A Moran Eye Center, Department of Ophthalmology and Visual Sciences, University of Utah, Salt Lake City, UT, USA; 2Temple University School of Medicine, Philadelphia, PA, USA; 3University of Arizona College of Medicine – Phoenix, Phoenix, AZ, USA; 4Wilmer Eye Institute, Johns Hopkins University, Baltimore, MD, USA; 5Virginia Commonwealth University School of Medicine, Richmond, VA, USAPurpose: To compare outcomes in visual acuity, refractive error, higher-order aberrations (HOAs, contrast sensitivity, and dry eye in patients undergoing laser in situ keratomileusis (LASIK using wavefront (WF guided VISX CustomVue and WF optimized WaveLight Allegretto platforms.Methods: In this randomized, prospective, single-masked, fellow eye study, LASIK was performed on 44 eyes (22 patients, with one eye randomized to WaveLight Allegretto, and the fellow eye receiving VISX CustomVue. Postoperative outcome measures at 3 months included uncorrected distance visual acuity (UDVA, corrected distance visual acuity (CDVA, refractive error, root-mean-square (RMS value of total and grouped HOAs, contrast sensitivity, and Schirmers testing.Results: Mean values for UDVA (logMAR were -0.067 ± 0.087 and -0.073 ± 0.092 in the WF optimized and WF guided groups, respectively (P = 0.909. UDVA of 20/20 or better was achieved in 91% of eyes undergoing LASIK with both lasers while UDVA of 20/15 or better was achieved in 64% of eyes using the Allegretto platform, and 59% of eyes using VISX CustomVue (P = 1.000. In the WF optimized group, total HOA increased 4% (P = 0.012, coma increased 11% (P = 0.065, and spherical aberration increased 19% (P = 0.214, while trefoil decreased 5% (P = 0.490. In the WF guided group, total HOA RMS decreased 9% (P = 0.126, coma decreased 18% (P = 0.144, spherical aberration decreased 27% (P = 0.713 and trefoil

  12. Controlled reshaping of the front surface of the cornea through its full-area ablation outside of the optical zone with a Gaussian ArF excimer laser beam

    Science.gov (United States)

    Semchishen, A. V.; Semchishen, V. A.

    2014-01-01

    We studied in vitro the response of the topography of the cornea to its full-area laser ablation (the laser beam spot diameter is commensurable with the size of the interface) outside of the central zone with an excimer laser having a Gaussian fluence distribution across the beam. Subject to investigation were the topographically controlled surface changes of the anterior cornea in 60 porcine eyes with a 5 ± 1.25-diopter artificially induced astigmatism, the changes being caused by laser ablation of the stromal collagen in two 3.5-mm-dia. circular areas along the weaker astigmatism axis. Experimental relationships are presented between the actual astigmatism correction and the expected correction for the intact optical zones 1, 2, 3, and 4 mm in diameter. The data for each zone were approximated by the least-squares method with the function d = a + bx. The coefficient b is given with the root-mean-square error. The statistical processing of the data yielded the following results: d = (0.14 ± 0.037)x for the 1-mm-dia. optical zone, (1.10 ± 0.036)x for the 2-mm-dia. optical zone, (1.04 ± 0.020)x for the 3-mm-dia. optical zone, and (0.55 ± 0.04)x for the 4-mm-dia. optical zone. Full astigmatism correction was achieved with ablation effected outside of the 3-mm-dia. optical zone. The surface changes of the cornea are shown to be due not only to the removal of the corneal tissue, but also to the biomechanical topographic response of the cornea to its strain caused by the formation of a dense pseudomembrane in the ablation area.

  13. Spectrum characteristic study of sodium-ethane excimer pairs

    Science.gov (United States)

    Hu, Shu; Gai, Baodong; Wang, Pengyuan; Li, Hui; Tan, Yannan; Liu, Jinbo; Guo, Jingwei

    2017-01-01

    Excimer pumped sodium laser (XPNaL) can accurately achieve lasing at 589.16 nm without any complicated control system to reduce the wavelength error, so XPNaL will provide a novel technical system for sodium beacon laser. In this paper, we studied the Na-C2H6 system, which was an efficient excimer pair. We excited the Na-C2H6 system using a pulsed dye laser with wavelength of 553 nm, and measured lifetime of sodium D2 line based on the fluorescence spectra. Meanwhile, we have also detected strong amplified spontaneous emission (ASE) signal in Na-C2H6 system, through the experimental study, the Na-C2H6 system is considered to own the potential to be utilized in high power XPNaL.

  14. Excimer Ladar Pointer Trackers

    Science.gov (United States)

    Grossman, Jon; Brindley, William E.

    Spaceborne optical pointing and tracking systems have historically used passive sensors. With the advent of space based laser programs ,such as submarine laser communication ( SLC SAT ) and laser atmospheric wind sounder ( LAWS ), it is now possible to conceive of laser based active pointing and tracking systems. In this paper we present some the advantages of going to an active pointer-tracker, the advantages of going to a short wavelength system, and what the performance of this system would be based on current technology.

  15. [Homoplastic keratomileusis for aphakic eyes with corneal leucoma].

    Science.gov (United States)

    Chen, J Q; Yang, B

    1994-09-01

    We performed homoplastic keratomileusis on 6 aphakic eyes with central corneal leucoma. The results showed that the post-operative corrected visual acuities were markedly increased to 0.3-0.5 in 3 cases and to 0.1-0.2 in another 3 cases. Since such patients were neither indicated to undergo intraocular lens implantation or penetrating keratoplasty for various reasons nor indicated for epikeratoplasty, homoplastic keratomileusis can be chosen for them.

  16. Development mechanism of high pressure argon plasma produced by irradiation of excimer laser. Ekishima reza ni yori seiseishita koatsuryoku arugon purazuma no seicho kiko

    Energy Technology Data Exchange (ETDEWEB)

    Yamada, J.; Tsuda, N.; Uchida, Y.; Furuhashi, H. (Aichi Inst. of Technology, Aichi (Japan)); Sahashi, T. (Daido Inst. of Technology, Aichi (Japan))

    1994-04-20

    The studies of a high temperature and high density laser plasma are being carried out centering around solid targets, but a high density plasma can be generated also by focused irradiation of a laser light onto a high pressure gas target. However, in this case, studies on a high pressure laser plasma using the ultra-violet beam are seldom conducted. In this paper, the generation mechanism of a plasma generated mainly behind the focal point of the lens is mentioned in case when the ultra violet laser beam is focused and irradiated onto a high pressure argon gas, and it has been compared for study with the plasma generated by a ruby laser. Part of the obtained results is as follows; it has been elucidated that the plasma generated behind the focal point by focusing and irradiating an ultra violet laser beam onto a high pressure argon gas is growing simultaneously by the radiation supported shock wave and the breakdown wave, same as the case of a visible laser beam. When the ultra violet beam with frequency higher than the plasma frequency is irradiated, a plasma grows in front of the focal point too. 6 refs., 9 figs.

  17. Effect of force on ablation depth for a XeCl excimer laser beam delivered by an optical fiber in contact with arterial tissue under saline

    NARCIS (Netherlands)

    Gijsbers, G. H.; van den Broecke, D. G.; Sprangers, R. L.; van Gemert, M. J.

    1992-01-01

    The effect of force applied to a 430 micron single fiber, delivering 60 pulses of 308 nm XeCl laser radiation at 20 Hz, on the ablation depth in porcine aortic tissue under saline has been investigated. Energy densities of 8, 15, 25, 28, 31, 37, and 45 mJ/mm2 were used. Force was applied by adding

  18. Effects of excimer laser irradiation on the expression of Th17, Treg, TGF-beta1, and IL-6 in patients with psoriasis vulgaris

    Science.gov (United States)

    Xiong, Guo-Xin; Li, Xin-Zhong

    2017-11-01

    The effects of laser irradiation on the expression of T helper 17 (Th17) and regulatory T (Treg) cells and their related cytokines, transforming growth factor beta 1 (TGF-β1) and interleukin-6 (IL-6), respectively, in the peripheral blood of patients with psoriasis vulgaris were investigated. 38 patients with psoriasis vulgaris in the stable state were selected as the treatment group that was treated twice a week for eight weeks. Another 38 healthy persons were chosen as the control group. Before and after treatment, the percentages of Th17 cells and Treg cells in the patients’ peripheral blood were detected using flow cytometry, the content of TGF-β1 and IL-6 in the patients’ sera were detected using enzyme-linked immunosorbent assay, and the extent and severity of lesions were determined by weighing the psoriasis area and severity index (PASI). After laser treatment, the percentage of Th17 cells, the Th17/Treg cell ratio and the level of IL-6 in the peripheral blood of patients with psoriasis in the treatment group were significantly lower than those of the same patients before the treatment (P  psoriasis vulgaris was 84.21%, and the PASI score was significantly lower (P  psoriasis vulgaris.

  19. Discharge-current characteristics in UV-preionized Kr/He, F2/He gas-mixtures and KrF excimer laser gas. Shigaisen yobi denri Kr/He, F2/He kongo kitai hoden oyobi KrF laser reiki hoden no denryu tokusei

    Energy Technology Data Exchange (ETDEWEB)

    Nakagawa, N.; Kawakami, H.; Yukimura, K. (Doshisha University, Kyoto (Japan))

    1992-08-15

    In order to study effects of Kr and F2 on discharge characteristics of KrF excimer laser gas, gap phenomena in Kr/He and F2/He gas-mixtures were observed and discharge current (I[sub d]) was measured. In the range where Kr concentration was over 10% in Kr/He gas, in which production of filamentation as well as glow discharge started, discontinuous change in I[sub d] in the second or third half cycle was observed. According to the results of experiments and model analyses, it was considered that the discontinuity of the current showed the transition point to filamentation. When F2 concentration was in the range between 0.1 and 0.3% in F2/He mixture gas, filamentation and arc with glow were observed. Sine-waveform I[sub d] ended in the first half cycle, and began to flow again after cessation or had almost constant current due to arc and others. When F2 was over 0.4%, only are discharge was observed. It was thus found that F2 has a large effect on discharge characteristics of KrF laser gas. 18 refs., 9 figs.

  20. Pressure and gap length dependence of gap breakdown voltage and discharge current of discharge-pumped KrF excimer laser. Hoden reiki KrF laser no zetsuen hakai den prime atsu to reiki denryu no atsuryoku, gap cho izon sei

    Energy Technology Data Exchange (ETDEWEB)

    Yukimura, K.; Kawakami, H. (Doshisha Univ., Tokyo (Japan)); Hitomi, K. (Kyoto Polytechnic College, Kyoto (Japan))

    1991-04-20

    On the gap destruction characteristics of UV-preionized discharge-pumped KrF excimer laser (charge transfer type) and the electric characteristics of the excited discharge, studies were made by changing the pressure (1.5-3 atm) and the discharge gap length (14-21 mm) of the discharge medium. (1) Gap breakdown voltage and the maximum current of the excited discharge give a similarity by a product of pressure and the gap length at the charge volatge. (2) Insulation breakdown of the gap occurs at the wave front of the applied voltage and the breakdown time gets delayed by the decreasing voltage applied. By setting the ionization index at constant value 20, the gap breakdown voltage is estimated at the error within 10%. (3) The relation between the maximum current, pressure and the gap length product changes the characteristics by the charge voltage of the primary condenser. With the result combined with the standardization of voltage/current of the excited discharge, the electric characteristics at the specific pressure and gap length can be readily known. 10 refs., 10 figs.

  1. Central corneal sensitivity after small incision lenticule extraction versus femtosecond laser-assisted LASIK for myopia: a meta-analysis of comparative studies

    National Research Council Canada - National Science Library

    He, Miao; Huang, Wenyong; Zhong, Xingwu

    2015-01-01

    ...) versus femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK) for myopia. Eligible studies were identified by systematically searching PubMed, the Cochrane Library, Embase and the Chinese Biomedicine Database...

  2. High power lasers in manufacturing

    OpenAIRE

    Chatwin, Chris R

    2017-01-01

    Lecture covers a brief history of lasers and the important beam parameters for manufacturing applications. It introduces the main laser types that are appropriate for manufacturing: carbon dioxide lasers, Nd YAG, Diode and fibre lasers, excimer lasers. It then looks at applications to different products and also micro-engineering

  3. Selective irradiation of radicals for biomedical treatment using vacuum ultraviolet light from an excimer lamp

    Science.gov (United States)

    Ono, Ryo; Tokumitsu, Yusuke; Zen, Shungo; Yonemori, Seiya

    2014-10-01

    In plasma medicine, radicals are considered to play important roles. However, the medical effect of each radical, such as OH and O, is unknown. To examine the effect of each radical, selective production of radicals is needed. We developed selective production of radicals for biomedical treatment using a vacuum ultraviolet (VUV) light emitted from an excimer lamp. Selective irradiation of OH radicals can be achieved by irradiating the 172-nm VUV light from a Xe2 excimer lamp to a humid helium flow in a quartz tube. The water molecules are strongly photodissociated by the VUV light to produce OH radicals. A photochemical simulation for the selective OH production is developed to calculate the OH density. The calculated OH density is compared with OH density measured using laser-induced fluorescence (LIF). Selective production of other radicals than OH is also discussed.

  4. EVALUATION OF SKIN-CANCER RISK RESULTING FROM LONG-TERM OCCUPATIONAL EXPOSURE TO RADIATION FROM ULTRAVIOLET-LASERS IN THE RANGE FROM 190 TO 400 NM

    NARCIS (Netherlands)

    Sterenborg, H. J.; de Gruijl, F. R.; Kelfkens, G.; van der Leun, J. C.

    1991-01-01

    The relative risk of occupational exposure to radiation from UV lasers was estimated using a mathematical model based on both epidemiological data and animal experiments. Calculations were performed for the 193 nm ArF excimer laser cornea shaping, the 308 nm XeCl excimer laser for coronary

  5. Testing relativity again, laser, laser, laser, laser

    NARCIS (Netherlands)

    Einstein, A.

    2015-01-01

    laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser,

  6. Refraction Measurements Of Excimer Area Ablated Animal Corneas Using A Modified Autorefractor

    Science.gov (United States)

    Clapham, Terrance N.; Herekar, Satish; Koons, Stephen

    1988-06-01

    Developing refractive surgery techniques usually requires pre-clinical trials with animals before human clinicals are performed. In order to assess the results of the surgery, an accurate and repeatable measurement of the resultant refraction must be made. Normal techniques such as retinoscopy, subjective examinations, and conventional autorefractions all run into problems when animals are involved. The authors have modified a conventional autorefractor and have made measurements on rabbits and monkeys both before and after refractive surgery treatments with an excimer laser. The results showed refractive changes with degrees of myopic correction.

  7. Laser in ophthalmology. Laser i oftalmologien

    Energy Technology Data Exchange (ETDEWEB)

    Syrdalen, P. (Rikshospitalet, Oslo (Norway))

    1991-09-01

    The article presents a brief history of the use of laser in ophthalmology in Norway, from the introduction of the first argon-photocoalulator in 1972 to the excimer laser in 1990. The argon-photocoagulator is in daily us in all Eye Departments in Norway and the main group of patients treated are those with diabetic retionopathy. Glaucoma has been treated with argon-laser with good results for the last ten years. YAG-laser, introduced in Norway in 1985, is used to treat secondary cataracts which occur after extracapsular cataract extractions and implantation of artificial lenses. In 1990, the excimer laser was introduced for refractive surgery (myopia, astigmatism). 4 refs., 6 figs., 1 tab.

  8. Deposition and characterization of ITO films produced by laser ablation at 355 nm

    DEFF Research Database (Denmark)

    Holmelund, E.; Thestrup Nielsen, Birgitte; Schou, Jørgen

    2002-01-01

    and at high substrate temperatures, the specific resistivity of the films, 2–3×10-4 Ω cm, is comparable to values obtained with excimer lasers, whereas the resistivities obtained at room temperature are somewhat higher than those of films produced by excimer lasers. The transmission coefficient of visible...... light, about 0.9, is also comparable to values for films deposited by excimer lasers. The crystalline structure of films produced at 355 nm is similar to that of samples produced by these lasers.......Indium tin oxide (ITO) films have been deposited by pulsed laser deposition (PLD) at 355 nm. Even though the absorption of laser light at the wavelength 355 nm is much smaller than that of the standard excimer lasers for PLD at 248 nm and 193 nm, high-quality films can be produced. At high fluence...

  9. The use of WaveLight® Contoura to create a uniform cornea: the LYRA Protocol. Part 2: the consequences of treating astigmatism on an incorrect axis via excimer laser

    Directory of Open Access Journals (Sweden)

    Motwani M

    2017-05-01

    Full Text Available Manoj Motwani Motwani LASIK Institute, San Diego, CA, USA Purpose: To show how an incorrect manifest astigmatism axis can cause an abnormal induced astigmatism on a new axis. Patients and methods: Four eyes of three patients were treated primarily with WaveLight® EX500 wavefront optimized (WFO treatments for astigmatism. All four eyes needed enhancements and were analyzed retrospectively via WaveLight® Contoura to determine the reason for the incorrect astigmatism treatment. Two of the eyes were retreated with topographic-guided ablation, and two were treated with WFO correction. Results: The eyes that had an incorrect manifest axis resulted in a new abnormal induced astigmatism on a wholly new axis. Treatment with topographic-guided ablation completely eliminated the newly induced astigmatism. Treatment with WFO of an abnormal induced astigmatism corrected the refraction but still left topographic evidence of the abnormal astigmatism behind. One eye was incorrectly treated for astigmatism due to coma affecting refraction when the patient was dilated. This eye had a normal induced astigmatism on a perpendicular axis and was corrected using WFO. The use of manifest refraction with WaveLight® Contoura topographic-guided ablation will lead to incorrect astigmatism correction when the manifest astigmatism and axis differ from the WaveLight® Contoura measured. Conclusion: Correction of an incorrect manifest refraction astigmatic axis does not simply create undercorrection of the astigmatism but induces an entirely new abnormal astigmatism on a different axis. Manifest refraction is less accurate and can lead to abnormal astigmatism when laser ablation is performed. Keywords: WaveLight Contoura, astigmatism treatment, asymmetric astigmatism, topographic guide ablation, higher order aberrations, Contoura with LYRA Protocol, LASIK, PRK

  10. Reversible femtosecond laser-assisted myopia correction: a non-human primate study of lenticule re-implantation after refractive lenticule extraction.

    Directory of Open Access Journals (Sweden)

    Andri K Riau

    Full Text Available LASIK (laser-assisted in situ keratomileusis is a common laser refractive procedure for myopia and astigmatism, involving permanent removal of anterior corneal stromal tissue by excimer ablation beneath a hinged flap. Correction of refractive error is achieved by the resulting change in the curvature of the cornea and is limited by central corneal thickness, as a thin residual stromal bed may result in biomechanical instability of the cornea. A recently developed alternative to LASIK called Refractive Lenticule Extraction (ReLEx utilizes solely a femtosecond laser (FSL to incise an intrastromal refractive lenticule (RL, which results in reshaping the corneal curvature and correcting the myopia and/or astigmatism. As the RL is extracted intact in the ReLEx, we hypothesized that it could be cryopreserved and re-implanted at a later date to restore corneal stromal volume, in the event of keratectasia, making ReLEx a potentially reversible procedure, unlike LASIK. In this study, we re-implanted cryopreserved RLs in a non-human primate model of ReLEx. Mild intrastromal haze, noted during the first 2 weeks after re-implantation, subsided after 8 weeks. Refractive parameters including corneal thickness, anterior curvature and refractive error indices were restored to near pre-operative values after the re-implantation. Immunohistochemistry revealed no myofibroblast formation or abnormal collagen type I expression after 8 weeks, and a significant attenuation of fibronectin and tenascin expression from week 8 to 16 after re-implantation. In addition, keratocyte re-population could be found along the implanted RL interfaces. Our findings suggest that RL cryopreservation and re-implantation after ReLEx appears feasible, suggesting the possibility of potential reversibility of the procedure, and possible future uses of RLs in treating other corneal disorders and refractive errors.

  11. Advances in femtosecond laser technology

    Directory of Open Access Journals (Sweden)

    Callou TP

    2016-04-01

    Full Text Available Thais Pinheiro Callou, Renato Garcia, Adriana Mukai, Natalia T Giacomin, Rodrigo Guimarães de Souza, Samir J Bechara Department of Ophthalmology, University of Sao Paulo, Sao Paulo, Brazil Abstract: Femtosecond laser technology has become widely adopted by ophthalmic surgeons. The purpose of this study is to discuss applications and advantages of femtosecond lasers over traditional manual techniques, and related unique complications in cataract surgery and corneal refractive surgical procedures, including: LASIK flap creation, intracorneal ring segment implantation, presbyopic treatments, keratoplasty, astigmatic keratotomy, and intrastromal lenticule procedures. Keywords: laser therapy, refractive surgical procedures, intracorneal ring, laser in situ keratomileusis, keratoplasty, presbyopia, cataract extraction, astigmatism surgery

  12. Femtosecond Lasers in Ophthalmology: Surgery and Imaging

    Science.gov (United States)

    Bille, J. F.

    Ophthalmology has traditionally been the field with prevalent laser applications in medicine. The human eye is one of the most accessible human organs and its transparency for visible and near-infrared light allows optical techniques for diagnosis and treatment of almost any ocular structure. Laser vision correction (LVC) was introduced in the late 1980s. Today, the procedural ease, success rate, and lack of disturbing side-effects in laser assisted in-situ keratomileusis (LASIK) have made it the most frequently performed refractive surgical procedure (keratomileusis(greek): cornea-flap-cutting). Recently, it has been demonstrated that specific aspects of LVC can take advantage of unique light-matter interaction processes that occur with femtosecond laser pulses.

  13. Near-infrared laser-induced fluorescence detection in column liquid chromatography. A comparison of various lasers and detection systems. II*. Pulsed lasers.

    NARCIS (Netherlands)

    Mank, A.J.G.; Velthorst, N.H.; Brinkman, U.A.T.; Gooijer, C.

    1995-01-01

    The applicability of two pulsed lasers, a XeCl-excimer/dye laser and a Nd:YAG/dye laser combination, as excitation sources for near-infrared (NIR) laser-induced fluorescence (LIF) detection in column liquid chromatography (LC) is studied. Using gradient LC, the best detection limit for the model

  14. Laser-induced breakdown spectra of Zn2 molecule in the violet region

    Indian Academy of Sciences (India)

    The study of excimer and van der Waals molecules such as Hg2, Cd2 and Zn2 are of current interest as they are potential candidates for the possible development of new high power excimer lasers. Group IIB metal dimers (Hg2, Cd2 and Zn2) have essentially repulsive ground states with very shallow van der Walls minima.

  15. LASIK

    Medline Plus

    Full Text Available ... surgery, FDA’s current LASIK activities , and FDA-approved lasers for LASIK . LASIK stands for Laser-Assisted In Situ Keratomileusis and is a procedure ... the front of the eye, using an excimer laser. A mechanical microkeratome (a blade device) or a ...

  16. The Impact of Flap Creation Methods for Sub-Bowman's Keratomileusis (SBK on the Central Thickness of Bowman's Layer.

    Directory of Open Access Journals (Sweden)

    Zhe Xu

    Full Text Available To determine the impact of flap creation methods for sub-Bowman's keratomileusis (SBK on central Bowman's layer thickness.SBK flaps were made by Moria microkeratome for 20 subjects and by femtosecond (FEMTO laser for 21 subjects. Corneal sublayer thicknesses were measured by ultra-high resolution optical coherence tomography before SBK and at 1 day, 1 week, 2 weeks, and 1 month afterwards. Each subject was imaged twice on each visit. Thicknesses of central epithelium, Bowman's layer, flap, and total cornea were calculated using a custom-made automated image processing algorithm. The repeatability of sublayer thickness measurements was tested by the intraclass correlation coefficient (ICC and by the coefficient of repeatability (CoR at 1 week post-SBK.ICCs of the Moria and FEMTO groups were ≥ 0.959 and ≥ 0.961 respectively for all sublayer measurements. The segmentation CoRs were less than 6.78% and 5.63% respectively. For both groups, microdistortions were present in the epithelium and Bowman's layer after SKB. The flap thickness of the Moria group was 9.8 μm (95% confidence interval: 4.8 - 14.8 μm thinner than the FEMTO group one day after SBK (independent samples t-test, P < 0.05. Bowman's layer became thicker by 1.6 ± 1.1 μm and 1.7 ± 1.6 μm one day post-SBK for the Moria and FEMTO groups (repeated ANOVA, P < 0.05 and then remained stable. Corneal and sublayer thickness were similar between the two groups.Central Bowman's layer thickness increased 1 day post-SBK. Flap creation by Moria microkeratome and femtosecond laser did not have significantly different impacts on Bowman's layer thickness following SBK.Chinese Clinical Trial Registry (ChiCTR NO: ChiCTR-OCH-14004525.

  17. The Impact of Flap Creation Methods for Sub-Bowman's Keratomileusis (SBK) on the Central Thickness of Bowman's Layer.

    Science.gov (United States)

    Xu, Zhe; Shen, Meixiao; Hu, Liang; Zhuang, Xiran; Peng, Mei; Hu, Di; Liu, Jing; Wang, Jianhua; Qu, Jia; Lu, Fan

    2015-01-01

    To determine the impact of flap creation methods for sub-Bowman's keratomileusis (SBK) on central Bowman's layer thickness. SBK flaps were made by Moria microkeratome for 20 subjects and by femtosecond (FEMTO) laser for 21 subjects. Corneal sublayer thicknesses were measured by ultra-high resolution optical coherence tomography before SBK and at 1 day, 1 week, 2 weeks, and 1 month afterwards. Each subject was imaged twice on each visit. Thicknesses of central epithelium, Bowman's layer, flap, and total cornea were calculated using a custom-made automated image processing algorithm. The repeatability of sublayer thickness measurements was tested by the intraclass correlation coefficient (ICC) and by the coefficient of repeatability (CoR) at 1 week post-SBK. ICCs of the Moria and FEMTO groups were ≥ 0.959 and ≥ 0.961 respectively for all sublayer measurements. The segmentation CoRs were less than 6.78% and 5.63% respectively. For both groups, microdistortions were present in the epithelium and Bowman's layer after SKB. The flap thickness of the Moria group was 9.8 μm (95% confidence interval: 4.8 - 14.8 μm) thinner than the FEMTO group one day after SBK (independent samples t-test, P < 0.05). Bowman's layer became thicker by 1.6 ± 1.1 μm and 1.7 ± 1.6 μm one day post-SBK for the Moria and FEMTO groups (repeated ANOVA, P < 0.05) and then remained stable. Corneal and sublayer thickness were similar between the two groups. Central Bowman's layer thickness increased 1 day post-SBK. Flap creation by Moria microkeratome and femtosecond laser did not have significantly different impacts on Bowman's layer thickness following SBK. Chinese Clinical Trial Registry (ChiCTR) NO: ChiCTR-OCH-14004525.

  18. Optical engineering of an excimer laser ophthalmic surgery system

    Science.gov (United States)

    Yoder, Paul R., Jr.

    1991-04-01

    We outline the interrelationships between the various major subsystems of an apparatus being developed in the USA for in vivo surgical recontouring of the human cornea to correct refractive errors and/or to remove damaged tissue. We then discuss five significant optical engineering problems that had to be solved during the design of this apparatus in order for the overall system to function properly.

  19. Laser materials processing with diode lasers

    OpenAIRE

    Li, Lin; Lawrence, Jonathan; Spencer, Julian T.

    1996-01-01

    Laser materials processing is currently dominated by CO2, Nd-YAG and Excimer lasers. Continuous advances in semiconductor laser technology over the last decade have increased the average power output of the devices annualy by two fold, resulting in the commercial availability of the diode lasers today with delivery output powers in excess of 60W in CW mode and 5kW in qasi-CW mode. The advantages of compactness, high reliability, high efficiency and potential low cost, due to the mass producti...

  20. Retina damage potential by ultra-short laser pulses in refractive surgery

    OpenAIRE

    Sander, Meike

    2013-01-01

    Since the beginning of the 1990s, laser in situ keratomileusis procedure (LASIK) has been successfully implemented in refractive eye surgery to correct ametropia. Nowadays this long time commanding treatment method is enhanced by implementing a new laser technology. It is based on correcting ametropia by applying ultrashort laser pulses in the fs-regime without using mechanical effect. Within this new technique the cutting process inside the cornea is achieved by a laser induced break...

  1. Mechanisms of tissue damage during ArF excimer endolaser microsurgery

    Science.gov (United States)

    Palanker, Daniel V.; Turovets, Igor; Lewis, Aaron

    1996-05-01

    The novel fiberoptic delivery system for the 193 nm excimer laser has been developed for vitreoretinal microsurgery. During the application of this laser in a liquid environment both the short-living cavitation bubbles and hydrogen gas-containing insoluble bubbles are produced. In present work we study the influence of these bubbles generated in free liquid on membranous tissue. Damage zones resulting from application of pulse trains at various repetition rates were investigated using vital stains which indicate the increase of cell membrane permeability. Cavitation bubbles were created by laser above the tissue in a highly absorbing liquid--Hartmann's solution with an addition of 7% albumin. These conditions simulate a situation in which a thin membrane separated from the underlying retina by layer of liquid is cut. After application of 50 pulses at 20 Hz at energy levels varying from 14 to 68 (mu) J per pulse we have detected cell damage at corresponding distances varying from 100 to 1200 microns. In Hartmann's solution (physiological medium), where the cavitation bubbles could not be formed at the same applied energies, the laser damage has been detected only at the distances varying from 150 to 200 microns. Penetration depth of the laser radiation in this solution is about 50 microns. The cells damage in this case probably has a photochemical nature. The difference in damage distance obtained at 1 and 20 Hz repetition rates can be explained by the influence of insoluble gas bubbles that grow at the tip exit and play a role of a transparent medium for the laser radiation. This effect probably determines the minimal distance at which the surgeon can apply the laser in standard physiological medium without being concerned with underlying cells damage. On the other hand, this phenomenon enable to destroy the upper level of cells in tissue without the deep penetrating mechanical influence associated with cavitation bubble-based tissue removal.

  2. Femtosecond laser corneal refractive surgery

    Science.gov (United States)

    Kurtz, Ron M.; Spooner, Greg J. R.; Sletten, Karin R.; Yen, Kimberly G.; Sayegh, Samir I.; Loesel, Frieder H.; Horvath, Christopher; Liu, HsiaoHua; Elner, Victor; Cabrera, Delia; Muenier, Marie-Helene; Sacks, Zachary S.; Juhasz, Tibor

    1999-06-01

    We evaluated the efficacy, safety, and stability of femtosecond laser intrastromal refractive procedures in ex vivo and in vivo models. When compared with longer pulsewidth nanosecond or picosecond laser pulses, femtosecond laser-tissue interactions are characterized by significantly smaller and more deterministic photodisruptive energy thresholds, as well as reduced shock waves and smaller cavitation bubbles. We utilized a highly reliable, all-solid-state femtosecond laser system for all studies to demonstrate clinical practicality. Contiguous tissue effects were achieved by scanning a 5 μm focused laser spot below the corneal surface at pulse energies of approximately 2 - 4 microjoules. A variety of scanning patterns was used to perform three prototype procedures in animal eyes; corneal flap cutting, keratomileusis, and intrastromal vision correction. Superior dissection and surface quality results were obtained for lamellar procedures (corneal flap cutting and keratomileusis). Preliminary in vivo evaluation of intrastromal vision correction in a rabbit model revealed consistent and stable pachymetry changes, without significant inflammation or loss of corneal transparency. We conclude that femtosecond laser technology may be able to perform a variety of corneal refractive procedures with high precision, offering advantages over current mechanical and laser devices and techniques.

  3. Pulsed laser ablation of LaSrCoO

    NARCIS (Netherlands)

    Span, E.A.F.; Roesthuis, Frank J.G.; Blank, David H.A.; Rogalla, Horst

    1999-01-01

    The ablation process of La0.5Sr0.5CoO3 by a spatial uniform 248 nm excimer laser beam has been characterized. Ablation rates, changes in the target surface morphology and composition have been studied as a function of the laser fluence. The dependence of the ablation rate on the laser fluence has

  4. Effects of laser wavelength and fluence on the growth of ZnO thin films by pulsed laser deposition

    NARCIS (Netherlands)

    Craciun, V.; Amirhaghi, S.; Craciun, D.; Elders, J.; Gardeniers, Johannes G.E.; Boyd, Ian W.

    Transparent, electrically conductive and c-axis oriented ZnO thin films have been grown by the pulsed laser deposition (PLD) technique on silicon and Corning glass substrates employing either a KrF excimer laser (λ = 248 nm) or a frequency-doubled Nd:YAG laser (λ = 532 nm). The crystalline

  5. Shadowgraphic imaging of material removal during laser drilling with a long pulse eximer laser

    NARCIS (Netherlands)

    Schoonderbeek, A.; Biesheuvel, C.A.; Hofstra, R.M.; Boller, Klaus J.; Meijer, J.

    2005-01-01

    After the development of a novel XeCl excimer laser with a nearly diffraction-limited beam and 175 ns pulse length, research was done on different industrial applications of this laser. Hole drilling, one of these applications, was studied extensively. A better understanding of the drilling process

  6. Internal Dynamics of Dendritic Molecules Probed by Pyrene Excimer Formation

    Directory of Open Access Journals (Sweden)

    Jean Duhamel

    2012-01-01

    Full Text Available This review exposes the current poor understanding of the internal segmental chain dynamics of dendrimers in solution probed by monitoring the process of excimer formation between pyrene labels covalently attached to the chain ends of dendrimers. The review begins by covering the bases of fluorescence and the kinetics of pyrene excimer formation before describing a procedure based on the Model Free (MF analysis that is used to analyze quantitatively the fluorescence decays acquired for dendrimers, the ends of which have been fully and covalently labeled with pyrene. Comparison of the various trends obtained by different research groups describing the efficiency of pyrene excimer formation with the generation number of dendrimers illustrates the lack of consensus between the few studies devoted to the topic. One possible reason for this disagreement might reside in the presence of minute amounts of unattached pyrene labels which act as potent fluorescent impurities and affect the analysis of the fluorescence spectra and decays in an uncontrolled manner. The review points out that the MF analysis of the fluorescence decays acquired with pyrene-labeled dendrimers enables one to account for the presence of unattached pyrene and to retrieve information about the internal segmental dynamics of the dendrimer. It provides guidelines that should enable future studies on pyrene-labeled dendrimers to yield results that are more straightforward to interpret.

  7. Development of EKC after Eximer Laser Photorefractive Surgery and Subsequent Recurrence of EKC-like Keratitis

    OpenAIRE

    Park, Sung Joon; Jang, Yoon Soo; Koh, Tae Hyuk; Kwon, Young A; Song, Sang Wroul

    2011-01-01

    This research focuses on four cases of patients having undergone eximer laser photorefractive surgery who were diagnosed with adenoviral keratoconjunctivitis during the postoperative period and who later developed epidemic keratoconjunctivitis (EKC)-like keratitis. Two of the patients had undergone laser-assisted subepithelial keratectomy (LASEK), one had undergone laser in situ keratomileusis and one had photorefractive keratectomy. After the surgery adenoviral keratoconjunctivitis and recur...

  8. Comparison of the femtosecond laser and mechanical microkeratome for flap cutting in LASIK

    OpenAIRE

    Li-Kun Xia; Jie Yu; Guang-Rui Chai; Dang Wang; Yang Li

    2015-01-01

    AIM: To compare refractive results, higher-order aberrations (HOAs), contrast sensitivity and dry eye after laser in situ keratomileusis (LASIK) performed with a femtosecond laser versus a mechanical microkeratome for myopia and astigmatism.METHODS: In this prospective, non-randomized study, 120 eyes with myopia received a LASIK surgery with the VisuMax femtosecond laser for flap cutting, and 120 eyes received a conventional LASIK surgery with a mechanical microkeratome. Flap thickness, visua...

  9. A review and meta-analysis of corneal cross-linking for post-laser vision correction ectasia

    Directory of Open Access Journals (Sweden)

    Qi Wan

    2017-09-01

    Conclusion: The study showed that CXL is a promising treatment to stabilize the keratectasia after Excimer Laser Refractive Surgery. Further long-term follow-up studies are necessary to assess the persistence of the effect of the CXL.

  10. Laser in operative dentistry

    Directory of Open Access Journals (Sweden)

    E. Yasini

    1994-06-01

    Full Text Available Today laser has a lot of usage in medicine and dentistry. In the field of dentistry, laser is used in soft tissue surgery, sterilization of canals (in root canal therapy and in restorative dentistry laser is used for cavity preparation, caries removal, sealing the grooves (in preventive dentistry, etching enamel and dentin, composite polymerization and removal of tooth sensitivity. The use of Co2 lasers and Nd: YAG for cavity preparation, due to creating high heat causes darkness and cracks around the region of laser radiation. Also due to high temperature of these lasers, pulp damage is inevitable. So today, by using the Excimer laser especially the argon floride type with a wavelength of 193 nm, the problem of heat stress have been solved, but the use of lasers in dentistry, especially for cavity preparation needs more researches and evaluations.

  11. International Symposium on Gas Flow and Chemical Lasers, 8th, Madrid, Spain, Sept. 10-14, 1990, Proceedings

    Science.gov (United States)

    Orza, Jose M.; Domingo, C.

    1991-03-01

    Papers are presented on current research developments and applications related to high-powered lasers. Recent advances in excimer laser technology, electron-beam-pumped excimer lasers, discharge technology for excimer lasers, and pulsed XeF lasers are examined. Consideration is given to short-wavelength lasers, chemical oxygen iodine lasers, and vibrational chemical lasers. Papers are presented on CO2, CO, N2O lasers, coupled CO2 lasers, laser induced perturbation in pulsed CO2 lasers, construction of sealed-off CO2 lasers, and computer modeling of discharge-excited CO gas flow. Topics discussed include gas-dynamic lasers, discharge and flow effects, matrix and laser optics and laser beam parameters. Laser-matter interactions, laser-induced surface plasma, plasma motion velocity along laser beams and thermocapillary effects are also discussed. Applications of laser technology are examined and high-speed laser welding, welding results, laser ablation, laser steel processing, and numerical modeling of laser-matter interaction in high-intensity laser applications are considered. (For individual items see A93-26381 to A93-26422)

  12. Intramolecular excimer and exciplex emission of 1,4-dipyrenyl substituted cyclohexasilane

    NARCIS (Netherlands)

    van Walree, C.A.; Kaats-Richters, V.E.M.; Jenneskens, L.W.; Williams, R.M.; van Stokkum, I.H.M.

    2002-01-01

    Intramolecular excimer emission is observed for cis-1,4-di(1-pyrenyl)decamethylcyclohexasilane in nonpolar solvents. Time-resolved fluorescence spectroscopy and kinetic modelling indicate that the driving force of excimer formation is very small, and that the process is governed by the flexibility

  13. Applications of lasers and electro-optics

    Science.gov (United States)

    Tan, B. C.; Low, K. S.; Chen, Y. H.; Ahmad, Harith; Tou, T. Y.

    Supported by the IRPA Programme on Laser Technology and Applications, many types of lasers have been designed, constructed and applied in various areas of science, medicine and industries. Amongst these lasers constructed were high power carbon dioxide lasers, rare gas halide excimer lasers, solid state Neodymium-YAG lasers, nitrogen lasers, flashlamp pumped dye lasers and nitrogen and excimer laser pumped dye lasers. These lasers and the associated electro-optics system, some with computer controlled, are designed and developed for the following areas of applications: (1) industrial applications of high power carbon dioxide lasers for making of i.c. components and other materials processing purposes -- prototype operational systems have been developed; (2) Medical applications of lasers for cancer treatment using the technique of photodynamic therapy -- a new and more effective treatment protocol has been proposed; (3) agricultural applications of lasers in palm oil and palm fruit-fluorescence diagnostic studies -- fruit ripeness signature has been developed and palm oil oxidation level were investigated; (4) development of atmospheric pollution monitoring systems using laser lidar techniques -- laboratory scale systems were developed; and (5) other applications of lasers including laser holographic and interferometric methods for the non destructive testing of materials.

  14. A PRELIMINARY STUDY FOR SIX SIGMA IMPLEMENTATION IN LASER IN SITU KERATOMILEUSIS (LASIK SURGERIES

    Directory of Open Access Journals (Sweden)

    Mehmet Tolga Taner

    2014-01-01

    Full Text Available The purpose of this study is to show how a private eye care center in Turkey developed a Six Sigma infrastructure to investigate the root causes of complications occuring during LASIK surgeries. To analyze the collected data, main tools of Six Sigma’s Define-Measure-Analyze-Improve-Control(DMAIC improvement cycle such as SIPOC table, Fishbone Diagram and, Failure, Mode and Effect Analysis were implemented. Experience of the refractive surgeons, type of microkeratome and hygiene of microkeratome were identified to be Critical-to-Quality (CTQ factors for a successful LASIK surgery. The most frequent complications of LASIK surgeries were found to be dry eye syndrome, subconjunctival haemorrhage and flap edge melt. The process sigma level was found to be 3.7135.

  15. Laser in-situ keratomileusis in patients with diabetes mellitus: a review of the literature

    National Research Council Canada - National Science Library

    Simpson, Rachel G; Moshirfar, Majid; Edmonds, Jason N; Christiansen, Steven M

    2012-01-01

    .... While the United States Food and Drug Administration considers diabetes a relative contraindication to LASIK surgery, there are several reports in the literature of LASIK being performed safely...

  16. [Clinical observation on the relation between laser in situ keratomileusis treating myopic anisometropia and binocular vision].

    Science.gov (United States)

    Huang, Jing; Lu, Wei

    2009-09-29

    To analyze the effect of LASIK on visual quality of anisometropia, and evaluate its clinical value in the view of visual quality. Prospective observational case series. Assayed the naked vision, glasses-corrected vision and binocular vision of 45 cases with anisometropia >or= 2.25D before and after the operation of LASIK. 91.57% of the eyes after the operation reached the vision >or= 0.8, which says a significant improvement for binocular vision after the operation (P anisometropia, there was no significant difference between simultaneous binocular visions (P = 0.431), but there was of great significance among combined, short and long distance stereopsis visions (P = 0.000). Binocular vision deteriorated as anisometropia increased (P anisometropia were better than that of glasses-corrected patients (P anisometropia and its therapeutic efficacy deserves to confirm.

  17. Visual quality after epipolis laser in situ keratomileusis surgery in mild and moderate myopia

    National Research Council Canada - National Science Library

    Yin-Liang Huang; Peng Li

    2015-01-01

    ...)were divided into two groups: mild myopia group(60 eyes)and moderate myopia group(60 eyes). Objective visual acuity, aberration, contrast sensitivity and glare sensitivity were measured before and 1wk...

  18. One-year experience in presbyopia correction with biaspheric multifocal central presbyopia laser in situ keratomileusis.

    Science.gov (United States)

    Luger, Michiel H A; Ewering, Tobias; Arba-Mosquera, Samuel

    2013-05-01

    To analyze simultaneous vision (distance and near) 1-year after biaspheric multifocal central presbyLASIK treatments for hyperopia and myopia with or without astigmatism. Patients were treated to correct distance ametropias and alleviating presbyopic symptoms simultaneously. All patients have been treated in Presby aberration-free mode using FemtoLASIK for Sphere from -7.00 to +3.25 diopters (D), astigmatism up to 3.00 D, and addition up to +2.75 D. No eye had previous corneal refractive surgery. Preoperative corneal curvature ranged between 40 and 48 D, with pachymetry thicker than 500 μm. Preoperative corrected distance visual acuity was 0.1 logarithm of the minimum angle of resolution (logMAR) or better, with near vision of 0.2 logRAD or better with addition up to +2.50 D. Sixty-six eyes treated bilaterally using PresbyMAX software were reviewed. For 31 patients (94%), 1-year follow-up was completed. At 1 year, 70% of patients achieved uncorrected distance visual acuity 0.1 logMAR or better, 84% patients obtained uncorrected near visual acuity 0.1 logRAD or better, and 83% of eyes were within 0.75 D of defocus. Postoperative mean spherical equivalent refraction was -0.47 ± 0.44 D. Stability was achieved from the 6-week follow-up. Eighty-five percent of patients achieved simultaneously uncorrected distance visual acuity 0.2 logMAR or better and uncorrected near visual acuity 0.2 logRAD or better. Patient selection and expectation management is essential to achieve patient satisfaction. Even though optically the results are predictable and good, some patients find it difficult to adapt to the compromise and others are dissatisfied by the minor loss of distance visual acuity. Certain individuals are best suited for PresbyMAX. A test with multifocal contact lenses or trial frames that creates slightly defocused images can be used to simulate postoperative visual impressions and verify patient acceptance.

  19. The Incidence of Central Serous Chorioretinopathy after Photorefractive Keratectomy and Laser In Situ Keratomileusis

    Directory of Open Access Journals (Sweden)

    Majid Moshirfar

    2012-01-01

    A chart review was performed to identify all patients with CSCR and a previous history of LASIK or PRK. Results. Over the 6-year study period, 1 of 4,876 eyes which had LASIK or PRK at the Moran Eye Center was diagnosed with CSCR. One other patient was referred from an outside center, developed CSCR symptoms one month after PRK. Both patients were managed conservatively with a final visual acuity of 20/20 or better. All other patients presented 4 or more years after refractive surgery. Conclusions. We report the first 2 CSCR cases developing within one month after PRK. The low incidence argues against a causal association. Topical corticosteroids or anxiety may elevate cortisol levels presenting therapeutic challenges for the management of CSCR after PRK or LASIK.

  20. Long term results of no-alcohol laser epithelial keratomileusis and photorefractive keratectomy for myopia

    Directory of Open Access Journals (Sweden)

    Leopoldo Spadea

    2015-06-01

    Full Text Available RESULTS: Twenty-one eyes and 22 eyes completed follow-up of 60mo in LASEK and PRK group respectively. Manifest refraction at 60mo follow-up was -0.01 and 0.26 in LASEK and PRK group respectively. In the LASEK group mean UDVA and mean CDVA after 60mo were 20/22 and 20/20 respectively (P>0.01. In the PRK group mean UDVA and mean CDVA at 60mo follow-up were 20/20 and 20/20 after 60mo (P>0.01. The efficacy indexes were 0.87 and 0.95, and the safety indexes were 1.25 and 1.4 respectively for LASEK group and PRK group.CONCLUSION:Both standard PRK and no-alcohol LASEK offer safe and effective correction of low-moderate myopia in the long term without any statistically significant difference between the two groups.

  1. Photo-induced growth of dielectrics with excimer lamps

    Science.gov (United States)

    Boyd, Ian W.; Zhang, Jun-Ying

    2001-08-01

    The underlying principles and properties of vacuum ultraviolet (VUV) and ultraviolet (UV) radiation (excimer lamps), generated by a dielectric barrier discharge in a rare-gas (Rg) or a mixture of Rg and halogen, are discussed. Compared with conventional sources, these excimer lamps offer narrow-band radiation at various wavelengths from 108-354 nm and over large areas with high efficiencies and high power densities. The variety of available wavelengths offers an enormous potential for new industrial applications in materials processing. Previously, photo-oxidation of silicon, germanium and silicon-germanium and photo-deposition of single- and multi-layered films of silicon oxide, silicon nitride, and silicon oxynitride have been demonstrated by using excimer lamps. This paper reviews the progress on excimer lamp-assisted growth of high dielectric constant (Ta2O5, TiO2 and PZT) and low dielectric constant (polyimide and porous silica) thin films by photo-CVD and sol-gel processing, summarizes the properties of photo-induced growth of Ta2O5 films and discusses the effect and mechanism of low temperature UV annealing with 172 nm radiation. Metal oxide semiconductor capacitors based on the photo-induced Ta2O5 films grown directly on Si at low temperatures exhibit excellent electrical properties. Leakage current densities as low as 5.2×10-7 A cm-2 and 2.41×10-7 A cm-2 at 1 MV cm-1 have been achieved for the as-grown Ta2O5 films deposited by photo-induced sol-gel processing and photo-CVD, respectively-several orders of magnitude lower than for any other as-grown films prepared by any other technique. A subsequent low temperature (400°C) UV annealing step improves these to 10-8 A cm-2. These values are comparable to those only previously achieved for films annealed at high temperatures between 600°C and 1000°C. These properties make the photo-induced growth of Ta2O5 layers suitable alternative to SiO2 for high density DRAM application.

  2. Excimer Emission using 20keV Electron Beam Excitation

    Science.gov (United States)

    Wieser, J.; Ulrich, A.; Murnick, D. E.

    1996-10-01

    A small, continuously emitting rare gas excimer light source has been developed. The gas is excited by a 20keV dc-electron beam. A 300nm thick, 1×1mm^2 SiNx foil sustaining a pressure difference up to 2bar, separates the target volume from the high vacuum part of the electron gun. Spectra of the rare gases Ar, Kr, and Xe have been studied. The monochromator detector system was intensity calibrated in the wavelength range from 115nm to 320nm. Electron beam currents of typically 1μA were used for excitation. When used as a VUV lamp on the second excimer continua, energy conversion efficiencies of 30% were obtained. Emissions originating from the so called left turning points have been clearly observed at 155, 173, and 222nm in Ar_2^*, Kr_2^*, and Xe_2^*, respectively. The so called third continua between 185nm and 240nm (Ar), 220nm and 250nm (Kr), and at 270nm (Xe) have been studied. A new continuum in Xe at 280nm was found. (Funded by the A.v.Humboldt Foundation and NSF (CTS 94-19440). The authors acknowledge support by H. Huggins, A. Liddle and W.L. Brown (Bell Laboratories, Lucent Technologies))

  3. Smartphone-enabled filterless fluorescence assay utilizing the pyrene excimer

    Science.gov (United States)

    Goertz, John P.; White, Ian M.

    2015-03-01

    Fluorescence microscopy offers a number of advantages for cell- and biomarker-based diagnostics with regards to ease of use and interpretation, sensitivity, and specificity. However, its use in low-resource settings is often hindered by the need for bulky microscopes with expensive excitation and filter setups. While many advances have been made towards utilizing smartphones as microscopes, there remains a reliance on complex attachments to facilitate fluorescence microscopy. Here, we report progress towards a filter-less fluorescent assay utilizing ultraviolet light, an unmodified smartphone, and pyrene-labeled aptamers. The pyrene monomer is excited at a wavelength of 350 nm and emits at approximately 390 nm; when two pyrene molecules are brought into close proximity, however, they form an excimer which emits at approximately 490 nm. We have engineered pyrene-conjugated DNA sequences such that the fluorophores, normally in monomeric configuration, are brought into proximity upon binding of the DNA to its target. The large Stokes shift between excitation and emission of the excimer allows us to detect such biorecognition events with an unfiltered smartphone camera, enabling the use of this assay in low-resource settings where portability and easeof- use are paramount.

  4. 193nm high power lasers for the wide bandgap material processing

    Science.gov (United States)

    Fujimoto, Junichi; Kobayashi, Masakazu; Kakizaki, Koji; Oizumi, Hiroaki; Mimura, Toshio; Matsunaga, Takashi; Mizoguchi, Hakaru

    2017-02-01

    Recently infrared laser has faced resolution limit of finer micromachining requirement on especially semiconductor packaging like Fan-Out Wafer Level Package (FO-WLP) and Through Glass Via hole (TGV) which are hard to process with less defect. In this study, we investigated ablation rate with deep ultra violet excimer laser to explore its possibilities of micromachining on organic and glass interposers. These results were observed with a laser microscopy and Scanning Electron Microscope (SEM). As the ablation rates of both materials were quite affordable value, excimer laser is expected to be put in practical use for mass production.

  5. Investigation of Pyrene Excimer formation in various manufacturing processes and ionic structures

    Science.gov (United States)

    Jang, Hyun-Sook; Nieh, Mu-Ping

    2013-03-01

    Electrospun pyrene (Py)/polystyrene/tetrabutylammonium hexafluorophosphate (TBAPF6) thin films can provide high-sensitivity and high-selectivity detection of nitro-aromatic explosives through fluorescence quenching of the Py excimers. However, we have found that the formation of Py excimers in Py/PS/TBAPF6 thin films depends greatly on the manufacturing processes. Our results indicate that high solvent vapor pressure promotes the Py excimer fluorescence, while high temperature (around or greater than Tg of the PS) has an opposite effect in absence of solvent - reducing the Py excimer fluorescence. Moreover, we have found that salts structure such as cation chain length, anion strength can significantly affect the formation of Py excimer both in solution and solid state, presumably due to self-aggregation of the salts and electrostatic interactions between ions and pyrene excimer. 13C-NMR and steady-state fluorescence result indicate that the salt induces peak shift to the downfield in the spectra and quenches the Py excimer intensity drastically. Ph.D. Candidate, Institute of Material Science, Polymer program

  6. A Review of Luminescent Anionic Nano System: d10 Metallocyanide Excimers and Exciplexes in Alkali Halide Hosts

    Directory of Open Access Journals (Sweden)

    Howard H. Patterson

    2013-06-01

    Full Text Available Dicyanoaurate, dicyanoargentate, and dicyanocuprate ions in solution and doped in different alkali halide hosts exhibit interesting photophysical and photochemical behavior, such as multiple emission bands, exciplex tuning, optical memory, and thermochromism. This is attributed to the formation of different sizes of nanoclusters in solution and in doped hosts. A series of spectroscopic methods (luminescence, UV-reflectance, IR, and Raman as well as theoretical calculations have confirmed the existence of excimers and exciplexes. This leads to the tunability of these nano systems over a wide wavelength interval. The population of these nanoclusters varies with temperature and external laser irradiation, which explains the thermochromism and optical memory. DFT calculations indicate an MLCT transition for each nanocluster and the emission energy decreases with increasing cluster size. This is in agreement with the relatively long life-time for the emission peaks and the multiple emission peaks dependence upon cluster concentration.

  7. Power and pulse energy scaling for high-volume UV-laser microprocessing

    Science.gov (United States)

    Delmdahl, Ralph; Haupt, Oliver; Bragin, Igor; Albrecht, Hans-Stephan

    2017-02-01

    In industrial laser micro processing, throughput is as important as process quality. Treating large areas in minimum time is pivotal in achieving reduced unit costs in high-volume production. Excimer lasers meet the requirements for clean and precise structuring and enable the smallest structures in an efficient way. The latest technical developments in high power excimer lasers is bound to take cost-efficient UV-laser micro processing to the next level and bridges the gap between achievable precision and achievable throughput. New excimer laser developments and beam concepts together with latest performance data for upscaling both UV power and UV pulse energy will be the topic of this paper against the background of upcoming market trends and high volume applications.

  8. Laser Ablation for Medical Applications

    Science.gov (United States)

    Hayashi, Ken-Ichi

    Medical applications of laser are measurement, laser surgery, in-situ monitoring, and processing of medical devices. In this paper, author briefly reviews the trends of medical applications, describes some new applications, and then discuss about the future trends and problems of medical applications. At present, the domestic market of laser equipment for medical applications is nearly 1/10 of that for industrial applications, which has registered significant growth continuously. Laser surgery as a minimum invasive surgery under arthroscope is expected to decrease the pain of patients. Precise processing such as cutting and welding is suitable for manufacturing medical devices. Pulsed laser deposition has been successfully applied to the thin film coating. The corneal refractive surgery by ArF excimer laser has been widely accepted for its highly safe operation. Laser ablation for retinal implant in the visual prosthesis is one of the promising applications of laser ablation in medicine. New applications with femtosecond laser are expected in the near future.

  9. Excimer lamp as an effective alternative treatment for severe alopecia areata

    Directory of Open Access Journals (Sweden)

    Tzu-Chien Hsu

    2015-09-01

    Full Text Available The treatment response of alopecia areata (AA is often unpredictable. The aim of this study was to report the efficacy of an excimer lamp in treating AA. Seventeen AA patients were included. The overall response rate was 41.1%, and the satisfactory response rate was 29.4%. In patients with severe AA, the response rate was 50%. The therapeutic effect of the excimer lamp was evident by internal control. The onset of improvement occurred after 2 months, and only mild side effects were noted. Our results suggest that the 308-nm excimer lamp is a safe alternative treatment for AA, including those with severe AA.

  10. Femtosecond Lasers and Corneal Surgical Procedures.

    Science.gov (United States)

    Marino, Gustavo K; Santhiago, Marcony R; Wilson, Steven E

    2017-01-01

    Our purpose is to present a broad review about the principles, early history, evolution, applications, and complications of femtosecond lasers used in refractive and nonrefractive corneal surgical procedures. Femtosecond laser technology added not only safety, precision, and reproducibility to established corneal surgical procedures such as laser in situ keratomileusis (LASIK) and astigmatic keratotomy, but it also introduced new promising concepts such as the intrastromal lenticule procedures with refractive lenticule extraction (ReLEx). Over time, the refinements in laser optics and the overall design of femtosecond laser platforms led to it becoming an essential tool for corneal surgeons. In conclusion, femtosecond laser is a heavily utilized tool in refractive and nonrefractive corneal surgical procedures, and further technological advances are likely to expand its applications. Copyright 2017 Asia-Pacific Academy of Ophthalmology.

  11. Defects of crystal structure of Hg1-xCdxTe thin layers growing by pulsed laser deposition

    NARCIS (Netherlands)

    Virt, IS; Rudyj, IO; Frugynskiji, MS; Kurilo, [No Value; Sagan, P; Zawislak, J; Kuzma, M

    2003-01-01

    Hg1-xCdxTe layers have been obtained by pulsed laser deposition method using two types of lasers: YAG:Nd3+ (tau = 250 mus or 40 ns) and excimer (tau = 25 ns). The crystal structures of layers were investigated by the electron diffraction method. The dependence of the laser beam parameters on the

  12. Monitoring excimer formation of perylene dye molecules within PMMA-based nanofiber via FLIM method

    Science.gov (United States)

    Inci, Mehmet Naci; Acikgoz, Sabriye; Demir, Mustafa Muamer

    2016-04-01

    Confocal fluorescence lifetime imaging microscopy method is used to obtain individual fluorescence intensity and lifetime values of aromatic Perylene dye molecules encapsulated into PMMA based nanofibers. Fluorescence spectrum of aromatic hydrocarbon dye molecules, like perylene, depends on the concentration of dye molecules and these dye molecules display an excimeric emission band besides monomeric emission bands. Due to the dimension of a nanofiber is comparable to the monomer emission wavelength, the presence of nanofibers does not become effective on the decay rates of a single perylene molecule and its lifetime remains unchanged. When the concentration of perylene increases, molecular motion of the perylene molecule is restricted within nanofibers so that excimer emission arises from the partially overlapped conformation. As compared to free excimer emission of perylene, time-resolved experiments show that the fluorescence lifetime of excimer emission of perylene, which is encapsulated into NFs, gets shortened dramatically. Such a decrease in the lifetime is measured to be almost 50 percent, which indicates that the excimer emission of perylene molecules is more sensitive to change in the surrounding environment due to its longer wavelength. Fluorescence lifetime measurements are typically used to confirm the presence of excimers and to construct an excimer formation map of these dye molecules.

  13. Anterior chamber gas bubbles during femtosecond laser flap creation in LASIK: video evidence of entry via trabecular meshwork.

    Science.gov (United States)

    Soong, H Kaz; de Melo Franco, Rafael

    2012-12-01

    Femtosecond laser photodisruption of corneal stroma during laser in situ keratomileusis flap creation is accompanied by the formation of cavitation gas bubbles consisting of carbon dioxide and water vapor. Entry of these bubbles into the anterior chamber is an infrequent complication. We present video evidence that these bubbles enter via the trabecular meshwork. Neither author has a financial or proprietary interest in any material or method mentioned. Copyright © 2012 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  14. Laser Induced Surface Chemical Epitaxy

    Science.gov (United States)

    1990-03-01

    eV was observed in this study for DMTe adlay ,,;s annealed at 423 K, a condition which is likely to produce a metallic Te adlayer , the Cd 3d5 /2...processes were studied by irradiating the adlayer with ultraviolet photons produced by a Questek excimer laser. These were introduced into the deposition...binding energy observed for similarly annealed DMCd adlayers was 405.1 eV. Based on room temperature measurements and ligand shift and electronegativity

  15. Laser characteristics and interferometric process and sensor applications

    Science.gov (United States)

    Glatz, Otto

    2005-04-01

    Begin Fiber Bragg Gratings (FBGs) are basic elements in DWDM technology. They are produced by UV illumination. UV light sources have been steadily improved to meet the demands of FBG writing industry. We want to characterize some parameters of interest of a simple, line-narrowed excimer laser source, its improvements and contribution to interferometric non-proximity FBG writing. Parameters of interest to be discussed are the temporal and spatial coherence length, the beam stability and spectrum control of produced FBG. With a temporal coherence length of ~ 5 mm it is possible to utilize cost efficient excimer laser technology for the interferometric non-proximity FBG writing process. Correspondingly the line-narrowed Excimer laser can replace expensive frequency doubled Argon ion lasers driving interferometric FBG writing set-ups in production and R & D. Beyond it FBGs for sensor applications play an important role. They have the potential for the measurement of strain / deformation and temperature with applications including monitoring of highways, bridges, aerospace components and chemical and biological sensors. We want to discuss the requirements for excimer lasers for this application: The spatial coherence length, beam profile, pointing and energy stability.

  16. UV laser ablation of parylene films from gold substrates

    Energy Technology Data Exchange (ETDEWEB)

    O. R. Musaev, P. Scott, J. M. Wrobel, and M. B. Kruger

    2009-11-19

    Parylene films, coating gold substrates, were removed by laser ablation using 248 nm light from an excimer laser. Each sample was processed by a different number of pulses in one of three different environments: air at atmospheric pressure, nitrogen at atmospheric pressure, and vacuum. The laser-induced craters were analyzed by optical microscopy and x-ray photoelectron spectroscopy. Multi-pulse ablation thresholds of gold and parylene were estimated.

  17. Very Heavily Doped N-Type GaAs Obtained With Pulsed Laser Annealing

    Science.gov (United States)

    Rys, Andrzej; Chin, Tim; Compaan, Alvin; Bhat, Ajit

    1988-08-01

    A study of carrier activation and mobility was performed in pulsed laser annealed samples of GaAs implanted with doses of Si and Se from 2.2x1012 to 6.0x1014 cm-2. The samples were annealed using a pulsed XeCl excimer laser ( λ=308 nm) and a pulsed dye laser ( λ=728 nm) with energy densities from 0.1 to 0.9 J/cm2 and a 10 nsec pulse. Very high carrier concentrations of 3x1019 and 1.5x1019 cm-3 were obtained for best n-type GaAs samples annealed with the dye laser and excimer laser, respectively. Dye laser consistently produced higher activation than excimer laser annealing. A transient reflectivity experiment was performed to identify the GaAs melt threshold and the melt phase dynamics of the GaAs,under the nitride cap. The threshold energies for cap damage were 0.34 and 0.12 J/cm2 for excimer and dye lasers, respectively. High carrier activation, as measured by Van der Pauw method, was achieved even for lightly doped samples although the room temperature Hall mobility was low. Raman spectroscopy was used to identify the threshold energies for the GaAs implant layer recrystallization and for optimum carrier activation.

  18. Lasers.

    Science.gov (United States)

    Passeron, T

    2012-12-01

    Lasers are a very effective approach for treating many hyperpigmented lesions. They are the gold standard treatment for actinic lentigos and dermal hypermelanocytosis, such as Ota nevus. Becker nevus, hyperpigmented mosaicisms, and lentigines can also be successfully treated with lasers, but they could be less effective and relapses can be observed. However, lasers cannot be proposed for all types of hyperpigmentation. Thus, freckles and café-au-lait macules should not be treated as the relapses are nearly constant. Due to its complex pathophysiology, melasma has a special place in hyperpigmented dermatoses. Q-switched lasers (using standard parameters or low fluency) should not be used because of consistent relapses and the high risk of post-inflammatory hyperpigmentation. Paradoxically, targeting the vascular component of the melasma lesion with lasers could have a beneficial effect. However, these results have yet to be confirmed. In all cases, a precise diagnosis of the type of hyperpigmentation is mandatory before any laser treatment, and the limits and the potential side effects of the treatment must be clearly explained to patients. Copyright © 2012 Elsevier Masson SAS. All rights reserved.

  19. [Lasers].

    Science.gov (United States)

    Passeron, T

    2012-11-01

    Lasers are a very effective approach for treating many hyperpigmented lesions. They are the gold standard treatment for actinic lentigos and dermal hypermelanocytosis, such as Ota nevus. Becker nevus, hyperpigmented mosaicisms, and lentigines can also be successfully treated with lasers, but they could be less effective and relapses can be observed. However, lasers cannot be proposed for all types of hyperpigmentation. Thus, freckles and café-au-lait macules should not be treated as the relapses are nearly constant. Due to its complex pathophysiology, melasma has a special place in hyperpigmented dermatoses. Q-switched lasers (using standard parameters or low fluency) should not be used because of consistent relapses and the high risk of post-inflammatory hyperpigmentation. Paradoxically, targeting the vascular component of the melasma lesion with lasers could have a beneficial effect. However, these results have yet to be confirmed. In all cases, a precise diagnosis of the type of hyperpigmentation is mandatory before any laser treatment, and the limits and the potential side effects of the treatment must be clearly explained to patients. Copyright © 2012 Elsevier Masson SAS. All rights reserved.

  20. Mid-infrared pulsed laser ablation of the arterial wall. Mechanical origin of "acoustic" wall damage and its effect on wall healing

    NARCIS (Netherlands)

    van Erven, L.; van Leeuwen, T. G.; Post, M. J.; van der Veen, M. J.; Velema, E.; Borst, C.

    1992-01-01

    Pulsed mid-infrared lasers are an alternative to excimer lasers for transluminal angioplasty. The mid-infrared lasers, however, were reported to produce "acoustic" wall damage that might impair the immediate and long-term results. To study the immediate and long-term effects on the arterial wall,

  1. Lasers and beam delivery options for polycrystalline thin-film scribing

    Science.gov (United States)

    Compaan, A. D.; Matulionis, I.; Nakade, S.

    1999-03-01

    We have investigated the use of several different types of lasers for scribing of the thin film materials: CdTe, CuInGaSe2, ZnO, SnO2, Mo, Al, and Au. The lasers included several types of Nd: YAG (1064 and 532 nm wavelengths), Cu vapor (511/578 nm), XeCl excimer (308 nm), and KrF excimer (248 nm). Pulse durations ranged from ˜0.1 nsec to ˜250 ns. We found that the Nd: YAG systems work well for almost all of the above materials except for the transparent conductor ZnO, for which the two excimer lasers showed good performance. Pulse duration was found generally not to be critical except for the case of CIGS on Mo where longer pulse durations appear advantageous.

  2. The Advanced Oxidation Process (UV-Ozonation Type) Assisted By Excimer Lamp

    Science.gov (United States)

    Ikematsu, Tomokazu; Hayashi, Nobuya; Ihara, Satoshi; Satoh, Saburoh; Yamabe, Chobei

    2003-10-01

    The advanced oxidation processes utilizing the excimer lamp was developed for water purification. The UV light with the wavelength of 222nm that destructs the hydrogen peroxide to hydroxyl radical realizes the AOPs. In this paper, the KrCl excimer lamp with the wavelength of 222 nm was adopted for UV-ozonation type AOP, in order to treat the water with organic acid (humic acid). The lamp was made of quartz glasses with a coaxial cylindrical shape. The grounded copper electrode was rolled on the outer side of the glass tube. The excimer gas flows in the gap of the glass tube between outer and inner electrodes. The UV light from the discharge was irradiated to ozonated water that flows inside the glass tube. The enhancement of reduction rate of the organic compound dissolved in water was achieved using UV excimer lamp with the wavelength of 222 nm. When the excimer gas pressure was 200 Torr, maximum discharge power was obtained and light emission intensity at 222 nm was highest. The reduction rate of the UV light irradiation (9 kV, 200 Torr) was larger than that of ozonation only, and the reduction rate was improved from 40

  3. Contrasting the beam interaction characteristics of selected lasers with a partially stabilised zirconia (PSZ) bio-ceramic

    OpenAIRE

    Lawrence, Jonathan

    2002-01-01

    Differences in the beam interaction characteristics of a CO2 laser, a Nd:YAG laser, a high power diode laser (HPDL) and an excimer laser with a partially stabilised zirconia (PSZ) bio-ceramic have been studied. A derivative of Beer-Lambert’s law was applied and the laser beam absorption lengths of the four lasers were calculated as 33.55 x 10-3 cm for the CO2 laser, 18.22 x 10-3 cm for the Nd:YAG laser, 17.17 x 10-3 cm for the HPDL and 8.41 x 10-6 cm for the excimer laser. It was determined g...

  4. A quencher-free molecular beacon design based on pyrene excimer fluorescence using pyrene-labeled UNA (unlocked nucleic acid)

    DEFF Research Database (Denmark)

    Karlsen, Kasper Kannegård; Okholm, Anders Hauge; Kjems, Jørgen

    2013-01-01

    A quencher-free molecular beacon capable of generating pyrene excimer fluorescence has been constructed using strategically positioned pyrene-UNA monomers. Hybridization of a fully complementary RNA target was accompanied by a pyrene excimer emission increase of more than 900%, and detection of R...... in living cells was demonstrated....

  5. A quencher-free molecular beacon design based on pyrene excimer fluorescence using pyrene-labeled UNA (unlocked nucleic acid)

    DEFF Research Database (Denmark)

    Karlsen, Kasper Kannegård; Okholm, Anders Hauge; Kjems, Jørgen

    2013-01-01

    A quencher-free molecular beacon capable of generating pyrene excimer fluorescence has been constructed using strategically positioned pyrene-UNA monomers. Hybridization of a fully complementary RNA target was accompanied by a pyrene excimer emission increase of more than 900%, and detection of RNA...

  6. Lasers in endodontics: an overview

    Science.gov (United States)

    Frentzen, Matthias; Braun, Andreas; Koort, Hans J.

    2002-06-01

    The interest in endodontic use of dental laser systems is increasing. Developing laser technology and a better understanding of laser effects widened the spectrum of possible endodontic indications. Various laser systems including excimer-, argon+-, diode-, Nd:YAG-, Er:YAG- and CO2-lasers are used in pulp diagnosis, treatment of hypersensitivity, pulp capping, sterilization of root canals, root canal shaping and obturation or apicoectomy. With the development of new delivery systems - thin and flexible fibers - for many different wavelengths laser applications in endodontics may increase. Since laser devices are still relatively costly, access to them is limited. Most of the clinical applications are laser assisted procedures such as the removing of pulp remnants and debris or disinfection of infected root canals. The essential question is whether a laser can provide improved treatment over conventional care. To perform laser therapy in endodontics today different laser types with adopted wavelengths and pulse widths are needed, each specific to a particular application. Looking into the future we will need endodontic laser equipment providing optimal laser parameters for different treatment modalities. Nevertheless, the quantity of research reports from the last decade promises a genuine future for lasers in endodontics.

  7. Laser scribing of polycrystalline thin films

    Science.gov (United States)

    Compaan, A. D.; Matulionis, I.; Nakade, S.

    2000-07-01

    We have investigated the use of several different types of lasers for scribing of the polycrystalline materials used for thin-film solar cells: CdTe, CuInGaSe 2 (CIGS), ZnO, SnO 2, Mo, Al, and Au. The lasers included four different neodymium-yttrium-aluminum garnet (Nd:YAG) (both 1064 and 532 nm wavelengths), a Cu vapor (511/578 nm), an XeCl excimer (308 nm), and a KrF excimer (248 nm). Pulse durations ranged from ˜0.1 to ˜250 ns. We found that the fundamental and frequency-doubled wavelengths of the Nd:YAG systems work well for almost all of the above materials except for the transparent conductor ZnO. The diode-laser-pumped Nd:YAG was particularly convenient to use. For ZnO the uv wavelengths of the two excimer lasers produced good results. Pulse duration was found generally not to be critical except for the case of CIGS on Mo where longer pulse durations (≥250 ns) are advantageous. The frequently observed problem of ridge formation along the edges of scribe lines in the semiconductor films can be eliminated by control of intensity gradients at the film through adjustment of the focus conditions.

  8. Laser ablation threshold of cultural heritage metals

    Science.gov (United States)

    Lorusso, A.; Nassisi, V.; Buccolieri, A.; Buccolieri, G.; Castellano, A.; Leo, L. S.; di Giulio, M.; Torrisi, L.; Caridi, F.; Borrielli, A.

    The present work has the purpose to evaluate experimentally the ablation threshold fluences of copper, silver, and their alloys in order to induce a safety laser cleaning of the metal artifacts avoiding damages to the bulkE We used two different pulsed lasers: a KrF excimer laser operating at 248 nm, 23 ns pulse duration and a Nd:YAG laser operating at 532 nm (second harmonic), 3 ns pulse. Preliminary experimental results about the laser cleaning of bronze coins will be reported. The laser cleaning consists on the reduction of the chlorine concentration from the surface of the coins. The laser cleaning, carried out by the KrF laser, provides a safe way of removing the chlorine concentration as the Energy Dispersive X-Ray Fluorescence analyses will demonstrate.

  9. Selective laser cleaning of chlorine on ancient coins

    Science.gov (United States)

    Aiello, Domenico; Buccolieri, Alessandro; Buccolieri, Giovanni; Castellano, Alfredo; Di Giulio, Massimo; Leo, Laura Sandra; Lorusso, Antonella; Nassisi, Gloria; Nassisi, Vincenzo; Torrisi, Lorenzo

    2007-05-01

    Results about the efficiency of the laser cleaning on the reduction of corrosion products from the surface of ancient coins are reported. In this work an ancient copper coin datable from 1500 to 1600 A.D. and a UV excimer laser were utilized. The goal of this work consists to study the potentiality of UV laser treatment in the reduction of the chlorine concentration on the coin surface which is the main responsible of the corrosion processes of the ancient coins. We used Energy Dispersive X-Ray Fluorescence (EDXRF) and X-Ray Diffraction (XRD) techniques to estimate the chemical composition of the coin surface, before and after UV excimer laser cleaning. In particular, we measured the chlorine, copper and calcium concentrations. We found that a radiation dose of about 19 J/cm2 was able to reduce the chlorine concentration from 2.3 % w/w to 0.6 % w/w without damaging the metal bulk.

  10. Unique effects of the chain lengths and anions of tetra-alkylammonium salts on quenching pyrene excimer.

    Science.gov (United States)

    Jang, Hyun-Sook; Zhao, Jing; Lei, Yu; Nieh, Mu-Ping

    2014-09-10

    Pyrene (Py) excimer, through its unique fluorescence quenching, exhibits high sensitivity and high selectivity in detecting specific electron-deficient molecules, providing a potential platform for sensing technology, optical switch, and probing hydrophobicity of molecular environment. In solution state, its quenching mechanism has been well-studied. However, there remain many unknown properties regarding the quenching mechanism of the solid-state Py excimer. In this paper, the effects of a series of tetra-alkylammonium salts (with a variety of chain lengths and anions) on Py excimer quenching are investigated to identify the controlling parameters of the fluorescence quenching in the binary system. Several experimental approaches including steady-state fluorescence spectroscopy, UV absorption, (13)C-nuclear magnetic resonance (NMR) spectra, X-ray diffraction, scanning electron microscopy, and time-dependent fluorescence decay are employed to seek for the fundamental understanding of the quenching mechanism. The result indicates a unique quenching effect of tetrabutylammonium cation on the pyrene excimer, and which is not observed in the other cations with different chain lengths (the same associated hexafluorophosphate anions). Meanwhile, hexafluorophosphate anion (in the presence of tetrabutylammonium) is able to effectively retain Py excimer fluorescence when the system is prepared by evaporating solvent at high temperature. It is also confirmed that dynamic quenching is involved in the process. Hydrophobic environment around Py molecules shows strong correlation with the formation of Py excimer. The knowledge obtained in this study provides the insights to how the interaction between salt and Py molecule affects the excimer fluorescence.

  11. Spectroscopic study of laser irradiated chromatin

    Science.gov (United States)

    Radu, Liliana; Mihailescu, I.; Gazdaru, Doina; Preoteasa, V.

    2013-04-01

    The effects of three UV excimer laser radiations, with wavelengths of 193, 248 and 282 nm respectively, on the structure of chromatin (the complex of deoxyribonucleic acid with proteins that exists in eukaryotic cells nuclei) were investigated. The chromatin was extracted from livers of Winstar rats. The spectroscopic methods used are: fluorescence (Förster) resonance energy transfer (FRET), time resolved fluorescence and steady-state fluorescence. A chromatin deoxyribonucleic acid radiolysis, a chromatin proteins damage and a change of the global chromatin structure on lasers action were indicated by this study. It exists some small differences between the actions of these three laser radiations.

  12. Spectroscopic study of laser irradiated chromatin

    Energy Technology Data Exchange (ETDEWEB)

    Radu, Liliana, E-mail: liliana1radu@gmail.com [V. Babes National Institute, Department of Molecular Genetics and Radiobiology (Romania); Mihailescu, I. [National Institute for Lasers, Plasma and Radiation Physics, Department of Lasers (Romania); Gazdaru, Doina [Faculty of Physics, Bucharest University, Department of Biophysics (Romania); Preoteasa, V. [V. Babes National Institute, Department of Molecular Genetics and Radiobiology (Romania)

    2013-04-15

    The effects of three UV excimer laser radiations, with wavelengths of 193, 248 and 282 nm respectively, on the structure of chromatin (the complex of deoxyribonucleic acid with proteins that exists in eukaryotic cells nuclei) were investigated. The chromatin was extracted from livers of Winstar rats. The spectroscopic methods used are: fluorescence (Foerster) resonance energy transfer (FRET), time resolved fluorescence and steady-state fluorescence. A chromatin deoxyribonucleic acid radiolysis, a chromatin proteins damage and a change of the global chromatin structure on lasers action were indicated by this study. It exists some small differences between the actions of these three laser radiations.

  13. Pustular Palmoplantar Psoriasis Successfully Treated with Nb-UVB Monochromatic Excimer Light: A Case-Report

    Directory of Open Access Journals (Sweden)

    Serena Gianfaldoni

    2017-07-01

    Full Text Available Barber’s palmoplantar pustulosis (PPP is a form of localised pustular psoriasis, affecting the palmar and plantar surfaces. It is a chronic disease, with a deep impact on the patients’ quality of life. The Authors discuss a case of Baber Psoriasis successfully treated with monochromatic excimer light.

  14. Applications of the femtosecond laser in corneal refractive surgery.

    Science.gov (United States)

    Kim, Peter; Sutton, Gerard L; Rootman, David S

    2011-07-01

    The femtosecond laser has become a rapidly and widely adopted technology for surgeons performing refractive surgery. With the advances in femtosecond lasers, clinical outcomes and safety with their use have improved. The purpose of this review is to outline the current surgical applications of the femtosecond laser in corneal refractive surgery. Many surgeons have adopted femtosecond technology for the creation of the laser in-situ keratomileusis flap secondary to its improved safety, precision and reproducibility. Other applications include astigmatic keratotomy, channel creation for the insertion of intrastromal corneal ring segments, femtosecond lenticule extraction, facilitating the insertion of corneal inlays as well as in intrastromal presbyopia correction (IntraCOR). Further novel applications continue to be developed. This review outlines the recent advances and applications of the femtosecond laser in corneal refractive surgery.

  15. Long Coherence Length 193 nm Laser for High-Resolution Nano-Fabrication

    Science.gov (United States)

    2008-06-27

    ArF excimer lasers . In this Phase I STTR we have successfully designed and modeled a solid-state laser source that exceeds our target specifications...briefly in section 6. More details of the fiber modeling and analysis work are given in the appendix. The solid-state196 nm laser system is discussed...will limit the pulse energy . Efficiency of the system is another potential problem, as is scalability in power. A third system would use a 946 nm

  16. Novel laser ion sources

    CERN Document Server

    Fournier, P; Kugler, H; Lisi, N; Scrivens, R; Rodríguez, F V; Düsterer, S; Sauerbrey, R; Schillinger, H; Theobald, W; Veisz, L; Tisch, J W G; Smith, R A

    2000-01-01

    Development in the field of high-power laser systems with repetition rates of several Hz and energies of few joules is highly active and opening, giving new possibilities for the design of laser ions sources. Preliminary investigations on the use of four different laser and target configurations are presented: (1) A small CO/sub 2/ laser (100 mJ, 10.6 mu m) focused onto a polyethylene target to produce C ions at 1 Hz repetition rate (CERN). (2) An excimer XeCl laser (6 J, 308 nm) focused onto solid targets (Frascati). (3) A femtosecond Ti: sapphire laser (250 mJ, 800 nm) directed onto a solid targets (Jena). (4) A picosecond Nd: yttrium-aluminum-garnet (0.3 J, 532 nm) focused into a dense medium of atomic clusters and onto solid targets (London). The preliminary experimental results and the most promising schemes will be discussed with respect to the scaling of the production of high numbers of highly charged ions. Different lasers are compared in terms of current density at 1 m distance for each charge state...

  17. DUV high power lasers processing for glass and CFRP

    Science.gov (United States)

    Kobayashi, Masakazu; Kakizaki, Kouji; Oizumi, Hiroaki; Mimura, Toshio; Fujimoto, Junichi; Mizoguchi, Hakaru

    2017-05-01

    A laser processing is widely applied to cutting, drilling, welding, bending and surface treatment in industry. Lasers with a wavelength of 1 μm are mainly used and the processing is realized by melting materials. This thermal process has a high productivity but the processed surface is hard to use for precision machining. This report is focusing on two materials which are classified in wide band gap. Ablation rate was measured with a laser microscope and an optical one. Excimer laser is expected to be a useful tool for these materials

  18. Discharge instabilities in high-pressure helium-fluorine laser gas mixtures

    NARCIS (Netherlands)

    Mathew, D.; Bastiaens, Hubertus M.J.; Peters, P.J.M.; Boller, Klaus J.

    2005-01-01

    Discharge instabilities in F2 based excimer gas lasers are investigated using a small-scale discharge system. After preionizing the gas volume, a fast rising voltage pulse initiates the discharge. The temporal development of the discharge is monitored via its fluorescence by an intensified CCD

  19. Small Incision Lenticule Extraction (SMILE) vs. Femtosecond Laser in Situ Keratomileusis (FS-LASIK) for treatment of myopia

    DEFF Research Database (Denmark)

    Hansen, Rasmus Søgaard; Lyhne, Niels; Justesen, Birgitte

    of myopia. All treatments were performed at the Department of Ophthalmology, Odense University Hospital from April 2011 to December 2013. Inclusion criteria: CDVA ≤ 0.10 (logMAR) before surgery and no other ocular conditions than myopia with or without astigmatism of maximum 3 D. Exclusion criteria: Eyes...... degrees of myopia and low degrees of astigmatism, and results were overall comparable 3 months after surgery. Financial disclosures: None....

  20. Small Incision Lenticule Extraction (SMILE) vs. Femtosecond Laser in Situ Keratomileusis (FS-LASIK) for treatment of myopia

    DEFF Research Database (Denmark)

    Hansen, Rasmus Søgaard; Justesen, Birgitte; Lyhne, Niels

    treatments were performed at the Department of Ophthalmology, Odense University Hospital from April 2011 to December 2013. Inclusion criteria: CDVA ≤ 0.10 (logMAR) before surgery and no other ocular conditions than myopia with or without astigmatism of maximum 3 D. Exclusion criteria: Eyes having undergone...... of astigmatism, and results were overall comparable 3 months after surgery. Financial disclosures: None....

  1. Corneal biomechanics after small-incision lenticule extraction versus Q-value–guided femtosecond laser-assisted in situ keratomileusis

    Directory of Open Access Journals (Sweden)

    Jun Zhang

    2016-12-01

    Conclusions: Both SMILE and Q-FS-LASIK resulted in a decrease in CH and the CRF at postoperative 1 day, with the decreases stabilizing after this point. There were no significant differences between the short term effects of SMILE and Q-FS-LASIK on corneal biomechanical properties.

  2. A modified risk assessment scoring system for post laser in situ keratomileusis ectasia in topographically normal patients

    Directory of Open Access Journals (Sweden)

    Mohammad Miraftab

    2014-01-01

    Conclusion: Our modified ectasia risk scoring system for patients with normal corneal topography can predict post LASIK ectasia risk with acceptable sensitivity and specificity. However, there are still unidentified risk factors for which further studies are required.

  3. Luminescence quenching of the triplet excimer state by air traces in gaseous argon

    Science.gov (United States)

    Amsler, C.; Boccone, V.; Büchler, A.; Chandrasekharan, R.; Regenfus, C.; Rochet, J.

    2008-02-01

    The influence of air contamination on the VUV scintillation yield in gaseous argon at atmospheric pressure is investigated. We determine with a radioactive α-source the photon yield for various partial air pressures and different reflectors and wavelength shifters. We find that the time constant of the slow scintillation component depends on gas purity and is a good indicator for the total VUV light yield, while the fast component is not affected. This dependence is attributed to impurities destroying the long-lived triplet argon excimer state. The population ratio between the slow and the fast decaying excimer states is determined for α-particles to be 5.5 ± 0.6 in argon gas at 1100 mbar and room temperature. The measured decay time constant of the slow component is 3.140 ± 0.067 μs at a partial air pressure of 2 × 10-6 mbar.

  4. Luminescence quenching of the triplet excimer state by air traces in gaseous argon

    Energy Technology Data Exchange (ETDEWEB)

    Amsler, C; Boccone, V; Buechler, A; Regenfus, C; Rochet, J [Physik-Institut der Universitaet Zuerich, Winterthurerstrasse 190, CH-8057 Zuerich (Switzerland); Chandrasekharan, R [Institute for Particle Physics, ETH-Zuerich, CH-8093 Zuerich (Switzerland)], E-mail: Claude.Amsler@cern.ch

    2008-02-15

    The influence of air contamination on the VUV scintillation yield in gaseous argon at atmospheric pressure is investigated. We determine with a radioactive {alpha}-source the photon yield for various partial air pressures and different reflectors and wavelength shifters. We find that the time constant of the slow scintillation component depends on gas purity and is a good indicator for the total VUV light yield, while the fast component is not affected. This dependence is attributed to impurities destroying the long-lived triplet argon excimer state. The population ratio between the slow and the fast decaying excimer states is determined for {alpha}-particles to be 5.5 {+-} 0.6 in argon gas at 1100 mbar and room temperature. The measured decay time constant of the slow component is 3.140 {+-} 0.067 {mu}s at a partial air pressure of 2 x 10{sup -6} mbar.

  5. Temporal fluctuations in excimer-like interactions between pi-conjugated chromophores

    CERN Document Server

    Stangl, Thomas; Schmitz, Daniela; Remmerssen, Klaas; Henzel, Sebastian; Hoeger, Sigurd; Vogelsang, Jan; Lupton, John M

    2015-01-01

    Inter- or intramolecular coupling processes between chromophores such as excimer formation or H- and J-aggregation are crucial to describing the photophysics of closely packed films of conjugated polymers. Such coupling is highly distance dependent, and should be sensitive to both fluctuations in the spacing between chromophores as well as the actual position on the chromophore where the exciton localizes. Single-molecule spectroscopy reveals these intrinsic fluctuations in well-defined bi-chromophoric model systems of cofacial oligomers. Signatures of interchromophoric interactions in the excited state - spectral red-shifting and broadening, and a slowing of photoluminescence decay - correlate with each other but scatter strongly between single molecules, implying an extraordinary distribution in coupling strengths. Furthermore, these excimer-like spectral fingerprints vary with time, revealing intrinsic dynamics in the coupling strength within one single dimer molecule, which constitutes the starting point ...

  6. High efficiency fluorescent excimer lamps: An alternative to mercury based UVC lamps

    Science.gov (United States)

    Masoud, N. M.; Murnick, D. E.

    2013-12-01

    A high efficiency xenon excimer lamp radiating at 172 nm, with an internal phosphor coating shifting to UVC has been demonstrated, showing the feasibility of a cost effective alternative to UVC mercury lamps. Fluorescent lamps so designed can be fabricated in various geometries with high efficiency. Unlike other xenon excimer lamps based on dielectric barrier discharges this new system is highly compatible with existing and proposed phosphors as it operates in an inert gas environment at modest temperature and is subject only to 172 nm primary radiation. Using a lamp coated with a UVC phosphor we have demonstrated the feasibility of germicidal and curing lamps with 40% energy conversion efficiency and high power density. These lamps are rapidly switchable, have long projected lifetimes and are compatible with dimmers.

  7. High efficiency fluorescent excimer lamps: An alternative to mercury based UVC lamps

    Energy Technology Data Exchange (ETDEWEB)

    Masoud, N. M. [UV Solutions Inc, Newark, New Jersey 07103 (United States); Physics and Chemistry Department, Milwaukee School of Engineering, Milwaukee, Wisconsin 53202 (United States); Murnick, D. E. [UV Solutions Inc, Newark, New Jersey 07103 (United States); Department of Physics, Rutgers University, Newark, New Jersey 07102 (United States)

    2013-12-15

    A high efficiency xenon excimer lamp radiating at 172 nm, with an internal phosphor coating shifting to UVC has been demonstrated, showing the feasibility of a cost effective alternative to UVC mercury lamps. Fluorescent lamps so designed can be fabricated in various geometries with high efficiency. Unlike other xenon excimer lamps based on dielectric barrier discharges this new system is highly compatible with existing and proposed phosphors as it operates in an inert gas environment at modest temperature and is subject only to 172 nm primary radiation. Using a lamp coated with a UVC phosphor we have demonstrated the feasibility of germicidal and curing lamps with 40% energy conversion efficiency and high power density. These lamps are rapidly switchable, have long projected lifetimes and are compatible with dimmers.

  8. Laser refractive surgery in diabetic patients: a review of the literature

    Directory of Open Access Journals (Sweden)

    Spadea L

    2012-11-01

    Full Text Available Leopoldo Spadea,1 Maria Pia Paroli21University of L’Aquila, Department of Biotechnological and Applied Clinical Sciences, Eye Clinic, L’Aquila, 2University of Rome “La Sapienza”, Department of Surgical Sciences, Eye Clinic, Rome, ItalyBackground: The purpose of this study was to evaluate the current recommendations regarding laser refractive surgery in patients with diabetes mellitus and to assess whether these patients make appropriate candidates for laser vision correction.Methods: A literature search was conducted to identify current research on the ocular complications of diabetes and original publications on laser refractive surgery in diabetic patients.Results: Diabetes was associated with several ocular complications. Initially the US Food and Drug Administration listed these complications as justification to advise against refractive surgery in patients with diabetes. However, recent studies on laser in situ keratomileusis in diabetic patients indicate that this procedure may be safe in diabetic patients with very well controlled systemic disease and no ocular manifestations.Conclusion: Laser refractive surgery may be performed safely in a very selected group of patients with diabetes.Keywords: diabetes, laser in situ keratomileusis, photorefractive keratectomy, refractive surgery

  9. One-dimensional modelling of DBDs in NeXe mixtures for excimer lamps

    OpenAIRE

    Belasri, A; Khodja, K; Bendella, S; Harrache, Z

    2010-01-01

    Abstract Dielectric barrier discharges (DBDs) are a promising technology for high-intensity sources of specific UV and VUV radiation. In this work, the microdischarge dynamics in DBDs for Ne?Xe mixtures under the close conditions of excimer lamp working has been investigated. The computer model including the cathode fall, the positive column and the dielectric is composed of two coupled sub-models. The first submodel describes the electrical properties of the discharge and is based on a fl...

  10. Pulsed laser deposition of rare earth compounds

    CERN Document Server

    Stone, L A

    2001-01-01

    Magnetostrictive thin films have been deposited using various techniques such as sputtering and evaporation but the use of laser deposition has been limited. This research presents the results from pulsed laser deposition (PLD) of TbFe sub 2 , DyFe sub 2 and Terfenol-D thin films using an infra red Transversely Excited Atmospheric (TEA) CO sub 2 laser at lambda approx 10.6 mu m and an ultra violet Argon-Fluoride (ArF) excimer laser at lambda approx 193 nm. Results have showed that the TEA CO sub 2 laser under the range of conditions studied is not suitable for the production of magnetostrictive films. The problems experienced are a mixture of mostly fracture debris at low fluences (F approx 20 Jcm sup - sup 2) and melt droplets at high fluences (F approx 60 Jcm sup - sup 2). In all cases the destruction of the target is a major problem, with the Terfenol-D targets being the worst affected. Thin films produced were all iron rich. The use of an excimer laser has proved more successful in providing stoichiometri...

  11. Matrix assisted pulsed laser evaporation processing of triacetate-pullulan polysaccharide thin films for drug delivery systems

    Energy Technology Data Exchange (ETDEWEB)

    Cristescu, R. [National Institute for Lasers, Plasma and Radiation Physics, 409 Atomistilor, P.O. Box MG-36, RO-077125, Bucharest-Magurele (Romania) and Institute of Physics, Academy of Sciences of Czech Republic, Na Slovance 2, 182 21 Prague 8 (Czech Republic)]. E-mail: rodica.cristescu@inflpr.ro; Dorcioman, G. [National Institute for Lasers, Plasma and Radiation Physics, 409 Atomistilor, P.O. Box MG-36, RO-077125, Bucharest-Magurele (Romania); Ristoscu, C. [National Institute for Lasers, Plasma and Radiation Physics, 409 Atomistilor, P.O. Box MG-36, RO-077125, Bucharest-Magurele (Romania); Axente, E. [National Institute for Lasers, Plasma and Radiation Physics, 409 Atomistilor, P.O. Box MG-36, RO-077125, Bucharest-Magurele (Romania); Grigorescu, S. [National Institute for Lasers, Plasma and Radiation Physics, 409 Atomistilor, P.O. Box MG-36, RO-077125, Bucharest-Magurele (Romania); Moldovan, A. [National Institute for Lasers, Plasma and Radiation Physics, 409 Atomistilor, P.O. Box MG-36, RO-077125, Bucharest-Magurele (Romania); Mihailescu, I.N. [National Institute for Lasers, Plasma and Radiation Physics, 409 Atomistilor, P.O. Box MG-36, RO-077125, Bucharest-Magurele (Romania); Kocourek, T. [Institute of Physics, Academy of Sciences of Czech Republic, Na Slovance 2, 182 21 Prague 8 (Czech Republic); Jelinek, M. [Institute of Physics, Academy of Sciences of Czech Republic, Na Slovance 2, 182 21 Prague 8 (Czech Republic); Albulescu, M. [National Institute for Chemical-Pharmaceutical R and D, 112 Vitan, 74373 Bucharest 3 (Romania); Buruiana, T. [Petru Poni Institute of Macromolecular Chemistry, Iasi 6600 (Romania); Mihaiescu, D. [University of Agriculture Sciences and Veterinary Medicine, 59 Marasti, Bucharest (Romania); Stamatin, I. [University of Bucharest, Faculty of Physics, P.O. Box MG-38, 3 Nano-SAE Research Center, Bucharest-Magurele (Romania); Chrisey, D.B. [US Naval Research Laboratory, Washington, DC 20375-5345 (United States)

    2006-04-30

    We report the first successful deposition of triacetate-pullulan polysaccharide thin films by matrix assisted pulsed laser evaporation. We used a KrF* excimer laser source ({lambda} = 248 nm, {tau} {approx} 20 ns) operated at a repetition rate of 10 Hz. We demonstrated by FTIR that our thin films are composed of triacetate-pullulan maintaining its chemical structure and functionality. The dependence on incident laser fluence of the induced surface morphology is analysed.

  12. Original papers A study on efficacy of 308 nm excimer light therapy in alopecia areata

    Directory of Open Access Journals (Sweden)

    Zo Nun Sanga

    2015-06-01

    Full Text Available Introduction. Alopecia areata (AA is an autoimmune condition characterized by T-cell-mediated attack on hair follicles. Objective. Evaluation of efficacy of 308 nm excimer light in the treatment of alopecia areata. Material and methods. Patches of AA were treated twice weekly, but not on 2 consecutive days, with UVB excimer 308 nm light. In all patients, half of the AA patch was irradiated and the other half was spared, covered with a black rubber shield and taken as a control. Therapy was started with an initial dose of 300 mJ/cm 2 , with an incremental dose of 100 mJ/cm 2 at every sitting until fine erythema appeared. Results. At the end of the treatment, one patient (3.33% at the test site showed > 50% hair regrowth vs. none at the control site. After a 2-month post-treatment period, successful hair regrowth (grades 3 and 4 was seen in 12 patients at test sites and in 2 patients at control sites. The differences were statistically significant (p < 0.05. After 4 months successful hair regrowth (grades 3 and 4 was seen in 16 patients at test sites and in 5 patients at control sites. The differences were statistically significant (p 0.05. Conclusions. Excimer light has the potential to stimulate hair regrowth in patches of alopecia areata.

  13. Development of laser materials processing and laser metrology techniques

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Cheol Jung; Chung, Chin Man; Kim, Jeong Mook; Kim, Min Suk; Kim, Kwang Suk; Baik, Sung Hoon; Kim, Seong Ouk; Park, Seung Kyu

    1997-09-01

    The applications of remote laser materials processing and metrology have been investigated in nuclear industry from the beginning of laser invention because they can reduce the risks of workers in the hostile environment by remote operation. The objective of this project is the development of laser material processing and metrology techniques for repairing and inspection to improve the safety of nuclear power plants. As to repairing, we developed our own laser sleeve welding head and innovative optical laser weld monitoring techniques to control the sleeve welding process. Furthermore, we designedand fabricated a 800 W Nd:YAG and a 150 W Excimer laser systems for high power laser materials processing in nuclear industry such as cladding and decontamination. As to inspection, we developed an ESPI and a laser triangulation 3-D profile measurement system for defect detection which can complement ECT and UT inspections. We also developed a scanning laser vibrometer for remote vibration measurement of large structures and tested its performance. (author). 58 refs., 16 tabs., 137 figs.

  14. Molecule-binding dependent assembly of split aptamer and γ-cyclodextrin: A sensitive excimer signaling approach for aptamer biosensors

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Fen [State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082 (China); Hubei Key Laboratory of Mine Environmental Pollution Control and Remediation, Environmental Science and Engineering College, Hubei Polytechnic University, Huangshi 435003 (China); Lian, Yan; Li, Jishan; Zheng, Jing; Hu, Yaping; Liu, Jinhua; Huang, Jin [State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082 (China); Yang, Ronghua, E-mail: Yangrh@pku.edu.cn [State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082 (China)

    2013-10-17

    Graphical abstract: Adenosine-binding aptamer was splitted into two fragments P2 and P3 which labeled pyrene molecules, mainly produce monomer signal. γ-CD cavity brings P2 and P3 in close proximity, allowing for weak excimer emission. In the presence of target, P2 and P3 are expected to bind ATP and form an aptamer/target complex, leads to large increase of the pyrene excimer fluorescence. -- Highlights: •We assembled split aptamer and γ-cyclodextrin fluorescence biosensors for ATP detection. •The biosensor increased quantum yield and emission lifetime of the excimer. •Time-resolved fluorescence is effective for ATP assay in complicated environment. -- Abstract: A highly sensitive and selective fluorescence aptamer biosensors for the determination of adenosine triphosphate (ATP) was developed. Binding of a target with splitting aptamers labeled with pyrene molecules form stable pyrene dimer in the γ-cyclodextrin (γ-CD) cavity, yielding a strong excimer emission. We have found that inclusion of pyrene dimer in γ-cyclodextrin cavity not only exhibits additive increases in quantum yield and emission lifetime of the excimer, but also facilitates target-induced fusion of the splitting aptamers to form the aptamer/target complex. As proof-of-principle, the approach was applied to fluorescence detection of adenosine triphosphate. With an anti-ATP aptamer, the approach exhibits excimer fluorescence response toward ATP with a maximum signal-to-background ratio of 32.1 and remarkably low detection limit of 80 nM ATP in buffer solution. Moreover, due to the additive fluorescence lifetime of excimer induced by γ-cyclodextrin, time-resolved measurements could be conveniently used to detect as low as 0.5 μM ATP in blood serum quantitatively.

  15. Influence of corneal collagen crosslinking with riboflavin and ultraviolet-a irradiation on excimer laser surgery.

    NARCIS (Netherlands)

    Kampik, D.; Ralla, B.; Keller, S.; Hirschberg, M.; Friedl, P.H.A.; Geerling, G.

    2010-01-01

    PURPOSE: Riboflavin/ultraviolet A (UVA) cross-linking (CXL) of corneal collagen is a novel method of stabilizing corneal mechanical properties and preventing progression of keratectasias. This study was conducted to investigate whether CXL influences ablation rate, flap thickness, and refractive

  16. Corneal ectasia after excimer laser keratorefractive surgery: histopathology, ultrastructure, and pathophysiology.

    Science.gov (United States)

    Dawson, Daniel G; Randleman, J Bradley; Grossniklaus, Hans E; O'Brien, Terrence P; Dubovy, Sander R; Schmack, Ingo; Stulting, R Doyle; Edelhauser, Henry F

    2008-12-01

    To evaluate the histopathology and ultrastructure of corneas developing ectasia after LASIK or photorefractive keratectomy (PRK). Retrospective case series. Thirteen specimens from 12 patients undergoing corneal transplantation for progressive ectasia after LASIK (12 specimens) or PRK (1 specimen) were obtained for histopathologic and ultrastructural evaluation. All 13 ectatic corneas were submitted in formalin for light microscopy. Nine specimens were bisected, and the second half was placed in 2.5% glutaraldehyde for transmission electron microscopy (TEM). Corneal histopathology, ultrastructure, and pathophysiology. Light microscopy of the post-LASIK specimens showed corneal epithelial hypoplasia and occasional foci of epithelial hyperplasia, Bowman's layer breaks, a normal stromal thickness of the LASIK flap, a normal thickness of the hypocellular primitive stromal scar, a thinned residual stromal bed (RSB), and larger than normal artifacteous interlamellar clefts in the RSB of the ectatic region. The post-PRK specimen showed similar findings with the addition of a thinned hypercellular fibrotic stromal scar. TEM showed thinning of the collagen lamellae and loss of lamellar number in the RSB of post-LASIK ectasia corneas or throughout the entire corneal stromal bed in the post-PRK ectasia cornea, with the posterior aspect of the corneal stroma being most affected. Histopathologic and ultrastructural studies suggest that interlamellar and interfibrillar biomechanical slippage occurs when the cornea becomes ectatic after LASIK or PRK in the postoperative stress-bearing regions of the corneal stroma. This 2-phase chronic biomechanical failure process is similar to that seen in keratoconus. Composite sciences classify this chronic biomechanical failure process as interfiber fracture. The authors have no proprietary or commercial interest in any materials discussed in this article.

  17. Clinical observation on photorefractive keratectomy with epithelial removal by excimer laser

    Directory of Open Access Journals (Sweden)

    Dong-Mei Wang

    2016-03-01

    Full Text Available AIM:To investigate the clinical outcomes after photorefractive keratectomy(PRKwith epithelial removal by phototherapeutic keratectomy(PTKfor 1a. METHODS:A prospective analysis for 16 consecutive patients(30 eyeswith myopia and myopic astigmatism from July 2012 to July 2014 in our hospital underwent transepithelial photorefractive keratectomy(T-PRK, PRK with epithelial removal by PTK. Uncorrected distant visual acuity(UCVA, haze formation and remaining manifest refractive spherical equivalent(MRSEwere recorded before and at 1,3,6 and 12mo after operations. RESULTS:There were no significant differences(P>0.05in patients had an postoperative UCVA≥0.5 at 1, 3, 6 and 12mo compared with preoperative best corrected visual acuity(BCVA, and the same as the patients had an UCVA≥1.0(P>0.006. There were significant differences in haze values between different postoperative times(F=16.751, P=0.000. The haze value at 1mo was 0.71±0.25, which was gradually reduced with the time, and no more than 2 grades. Postoperative MRSE at 1mo was 0.9±0.87D, compared with 0.5±0.65D at 3mo, the difference was statistically significant(t=2.017, P=0.048. While the difference was not statistically significant(F=2.389, P=0.098among MRSE at 3, 6(0.5±0.45Dand 12mo(0.25±0.4D.CONCLUSION:The study obtained good clinical visual acuity. It shows slightly hyperopic shift and corneal haze at 1mo postoperatively. Large sample and grouped clinical research should be taken for the long-term stability of refraction and visual quality.

  18. Influence of chemical polymer composition on integrated waveguide formation induced by excimer laser surface irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Hessler, S.; Rosenberger, M.; Belle, S. [Applied Laser and Photonics Group, University of Applied Sciences Aschaffenburg, Wuerzburger Strasse 45, 63743 Aschaffenburg (Germany); Schmauss, B. [Institute of Microwaves and Photonics, University of Erlangen-Nuremberg, Cauerstrasse 9, 91058 Erlangen (Germany); Hellmann, R. [Applied Laser and Photonics Group, University of Applied Sciences Aschaffenburg, Wuerzburger Strasse 45, 63743 Aschaffenburg (Germany)

    2015-11-30

    Graphical abstract: - Highlights: • Optical analysis of two different PMMA materials. • Determination of the chemical polymer compositions via {sup 1}H NMR spectroscopy. • Comparison of UV induced refractive index profiles using phase-shifting interferometry. • Optical characterization of the irradiated surface: average roughness, surface compaction. • Cut-back attenuation measurements confirm superior light guiding performance. - Abstract: We show that the chemical composition and the amount of residual monomers in polymethylmethacrylate significantly affect the evolution of optical waveguide formation induced by UV surface irradiation. We employ an interferometric approach in Mach-Zehnder configuration to determine the refractive index depth profile in different planar polymethylmethacrylate materials. Our results reveal a distinctive different surface and buried waveguide formation for materials having different monomer content. In particular, we find that for smaller residual monomer content buried waveguide formation is less pronounced, which is in turn preferential for a selective light guidance in planar polymer structures. Attenuation measurements confirm a difference in attenuation coefficient of 0.5 dB/cm.

  19. A new method of cornea modulation with excimer laser for simultaneous correction of presbyopia and ametropia.

    Science.gov (United States)

    Uthoff, Detlef; Pölzl, Markus; Hepper, Daniel; Holland, Detlef

    2012-11-01

    To investigate the outcomes of simultaneous correction of presbyopia and ametropia by a bi-aspheric cornea modulation technique, based on the creation of a central area hyperpositive for near vision and leaving the pericentral cornea for far vision in hyperopic, emmetropic, and myopic presbyopic patients. Sixty eyes of 30 patients were treated with the PresbyMAX technique by one surgeon (D.U.) at the Eye Hospital Bellevue, Kiel, Germany. Twenty eyes with hyperopic presbyopia, 20 eyes with emmetropic presbyopia, and 20 eyes with myopic presbyopia underwent Femto-Lasik, and were assessed up to 6 months postoperatively. All eyes underwent cornea treatment using the PresbyMAX® software, delivering a bi-aspheric multifocal ablation profile developed by SCHWIND eye-tech-solutions (Kleinostheim, Germany). All flaps were created by Ziemer LDV Femtolaser (Port, Switzerland). The mean binocular distance of uncorrected visual acuity (DUCVA) improved in the hyperopic group from 0.28 ± 0.29 logMAR to -0.04 ± 0.07 logMAR, in the emmetropic group from -0.05 ± 0.07 logMAR to 0.02 ± 0.11 logMAR, and in the myopic group from 0.78 ± 0.27 logMAR to 0.09 ± 0.08 logMAR. The mean binocular near uncorrected visual acuity (NUCVA) increased in the hyperopic group from 0.86 ± 0.62 logRAD to 0.24 ± 0.23 logRAD, and in the emmetropic group from 0.48 ± 0.14 logRAD to 0.18 ± 0.11 logRAD. The myopic presbyopes showed a decrease of the mean binocular NUCVA from 0.04 ± 0.19 logRAD to 0.12 ± 0.18 logRAD. The mean postoperative spherical equivalent for distance refraction was -0.13 ± 0.61 D for the hyperopic presbyopia, -0.43 ± 0.35 D for the emmetropic presbyopia, and -0.68 ± 0.42 D for the myopic presbyopia group, whereas the software took aim at -0.50 D in all groups. In presbyopic patients without symptomatic cataracts, but refractive errors, PresbyMAX® will decrease the presbyopic symptoms and correct far distance refraction in the same treatment, offering spectacle-free vision in daily life in most of the treated patients. Further investigation is necessary to evaluate the overall benefit of this procedure.

  20. Functionally gradient materials of new generation fabricated by ablation and pulsed laser deposition

    Science.gov (United States)

    Major, Boguslaw; Mroz, Waldemar; Wierzchon, Tadeusz; Ebner, Reinhold

    2003-10-01

    Physical basis of desorption and ablation are presented focusing mostly on the primary and secondary mechanisms and short pulses interaction with materials. Facilities used in pulse laser deposition (PLD) are discussed in respect to the PLD system working with an excimer laser which has been just set up at the Institute of Optoelectronics Military University of Technology. Directions of present and future applications are shown on the basis of the Proceedings of the last two Conferences on Laser Ablation COLA i.e. in Germany (1999) and Japan (2001). Own examinations on the PLD layers of FeAl and Ni3Al intermetallics produced using an excimer KrF as well as of TiN deposited by means of a Nd:YAG laser are presented.

  1. Organelle-specific injury to melanin-containing cells in human skin by pulsed laser irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Murphy, G.F.; Shepard, R.S.; Paul, B.S.; Menkes, A.; Anderson, R.R.; Parrish, J.A.

    1983-12-01

    Physical models predict that ultraviolet laser radiation of appropriately brief pulses can selectively alter melanin-containing cellular targets in human skin. Skin of normal human volunteers was exposed to brief (20 nanosecond) 351-nm wave length pulses from a XeF excimer laser, predicting that those cells containing the greatest quantities of melanized melanosomes (lower half of the epidermis) would be selectively damaged. Transmission electron microscopy revealed the earliest cellular alteration to be immediate disruption of melanosomes, both within melanocytes and basal keratinocytes. This disruption was dose dependent and culminated in striking degenerative changes in these cells. Superficial keratinocytes and Langerhans cells were not affected. It was concluded that the XeF excimer laser is capable of organelle-specific injury to melanosomes. These findings may have important clinical implications in the treatment of both benign and malignant pigmented lesions by laser radiations of defined wave lengths and pulse durations.

  2. Selectively deposited copper on laser-treated polyimide using electroless plating

    Science.gov (United States)

    Zhao, Gang; Phillips, Harvey M.; Zheng, HongYu; Tam, Siu Chung; Liu, Wen Qing; Wen, Gongling; Gong, Zhiben; Lam, Yee Loy

    2000-06-01

    Many reviews about the interconnection line fabrication by laser processing method were reported recently. UV laser process polyimide has been studied thoroughly during the past decade. In this report, we discussed the utilization of surface potential changing on polyimide film irradiated by excimer KrF laser and metallized the UV laser treated polyimide surface by electroless copper deposition. A new negatively charged polymer stabilized Pd solution was applied as catalyst in this experiment. We also produced pattern-wised fine line on KrF laser induced PI surface using this method.

  3. Laser Flash Photolysis of Hydrogen Peroxide to Oxidize Protein Solvent-Accessible Residues on the Microsecond Timescale

    National Research Council Canada - National Science Library

    Hambly, David M; Gross, Michael L

    2005-01-01

    ... to unfold, exposing residues that are protected in the native protein. To circumvent this possibility, we developed a method using a 248 nm KrF excimer laser to cleave hydrogen peroxide at low concentrations (15 mM, 0. 04...

  4. Evaluation of the performance of small diode pumped UV solid state (DPSS) Nd:YAG lasers as new radiation sources for atmospheric pressure laser ionization mass spectrometry (APLI-MS).

    Science.gov (United States)

    Kersten, Hendrik; Lorenz, Matthias; Brockmann, Klaus J; Benter, Thorsten

    2011-06-01

    The performance of a KrF* bench top excimer laser and a compact diode pumped UV solid state (DPSS) Nd:YAG laser as photo-ionizing source in LC-APLI MS is compared. The commonly applied bench-top excimer laser, operating at 248 nm, provides power densities of the order of low MW/cm(2) on an illuminated area of 0.5 cm(2) (8 mJ/pulse, 5 ns pulse duration, beam waist area 0.5 cm(2), 3 MW/cm(2)). The DPSS laser, operating at 266 nm, provides higher power densities, however, on a two orders of magnitude smaller illuminated area (60 μJ/pulse, 1 ns pulse duration, beam waist area 2 × 10(-3) cm(2), 30 MW/cm(2)). In a common LC-APLI MS setup with direct infusion of a 10 nM pyrene solution, the DPSS laser yields a significantly smaller ion signal (0.9%) and signal to noise ratio (1.4%) compared with the excimer laser. With respect to the determined low detection limits (LODs) for PAHs of 0.1 fmol using an excimer laser, LODs in DPSS laser LC-APLI MS in the low pmol regime are expected. The advantages of the DPSS laser with respect to applicability (size, cost, simplicity) may render this light source the preferred one for APLI applications not focusing on ultimately high sensitivities. Furthermore, the impact of adjustable ion source parameters on the performance of both laser systems is discussed in terms of the spatial sensitivity distribution described by the distribution of ion acceptance (DIA) measurements. Perspectives concerning the impact on future APLI-MS applications are given.

  5. Advances in refractive surgery: microkeratome and femtosecond laser flap creation in relation to safety, efficacy, predictability, and biomechanical stability.

    Science.gov (United States)

    Stonecipher, Karl; Ignacio, Teresa S; Stonecipher, Megan

    2006-08-01

    Methods of flap creation have changed over the years from the evolution of the mechanical microkeratome to the introduction of the IntraLase femtosecond laser keratome, both of which have different mechanisms of action to create corneal resections. Previous studies report the advantages and disadvantages of the mechanical microkeratome and the IntraLase femtosecond laser. The critical components in laser in-situ keratomileusis surgery remain the same, however: safety, efficiency, predictability, and biomechanical stability. Keratoectasia and flap efficiency remain a constant safety concern in laser in-situ keratomileusis surgery. Unexpectedly thick flaps as well as variable thickness continue to be a concern with safety in relation to microkeratome technology. Epithelial preservation, flap complications, and newer issues such as Transient Light Sensitivity Syndrome are safety concerns of flap creation. Improved outcomes with regards to vision, induced astigmatism, induced higher-order aberrations, and enhancement rates are seen to favor predictability of femtosecond technologies over the microkeratome. Recent biomechanical studies show improved healing with femtosecond laser flap creation compared with blade-assisted flap creation. The aim of this review is to summarize the key components for both the microkeratome and the femtosecond laser and to update on the recent advances reported on these topics.

  6. [Results of residual ametropia correction using CIRCLE technology after femtosecond laser SMILE surgery].

    Science.gov (United States)

    Kostin, O A; Rebrikov, S V; Ovchinnikov, A I; Stepanov, A A; Takhchidi, Kh P

    to evaluate functional results of reoperation performed according to the CIRCLE technology and using the VisuMax femtosecond laser and MEL-80 excimer laser in cases of regression of the refractive effect after SMILE surgery. We studied a group of post-SMILE patients. In those, who showed regression of the refractive effect at 1 year, reoperation was performed according to the CIRCLE technology and using the VisuMax femtosecond laser. The corneal flap was separated from the stromal bed and turned aside. Excimer laser ablation of the stromal bed was performed with the MEL 80 machine. The corneal flap was then placed back and rinsed from both sides. Uncorrected (UCVA) and corrected (BCVA) visual acuity as well as spherical equivalent (SE) were estimated before reoperation, on day 1, and at 1 month. After reoperation, BCVA and UCVA improved. Patient refraction became close to emmetropia. Specifically, UCVA was 0.23±0.18 at baseline (i.e. 1 year after SMILE) and 0.93±0.11 after the CIRCLE procedure (pCIRCLE, respectively (p0.05). Reoperation performed according to the CIRCLE technology and using the VisuMax femtosecond laser and MEL-80 excimer laser provides an increase in visual acuity in case of post-SMILE regression of the refractive effect.

  7. Laser refractive surgery in diabetic patients: a review of the literature.

    Science.gov (United States)

    Spadea, Leopoldo; Paroli, Maria Pia

    2012-01-01

    The purpose of this study was to evaluate the current recommendations regarding laser refractive surgery in patients with diabetes mellitus and to assess whether these patients make appropriate candidates for laser vision correction. A literature search was conducted to identify current research on the ocular complications of diabetes and original publications on laser refractive surgery in diabetic patients. Diabetes was associated with several ocular complications. Initially the US Food and Drug Administration listed these complications as justification to advise against refractive surgery in patients with diabetes. However, recent studies on laser in situ keratomileusis in diabetic patients indicate that this procedure may be safe in diabetic patients with very well controlled systemic disease and no ocular manifestations. Laser refractive surger