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Sample records for excimer laser corneal

  1. Corneal wound healing after excimer laser keratectomy.

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    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.

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

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    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

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

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    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.

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

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    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.

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

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    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.

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

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    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.

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

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    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.

  8. Excimer lasers for refractive surgery

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    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.

  9. 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.

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

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    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.

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

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    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.

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

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    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

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

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    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.

  14. Excimer Laser Technology

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    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.

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

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    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.

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

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    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.

  17. Excimer Laser Etching

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    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.

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

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    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. Mitomycin-C in corneal surface excimer laser ablation techniques: a report by the American Academy of Ophthalmology.

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    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

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

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    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

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

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    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. Corneal ectasia after excimer laser keratorefractive surgery: histopathology, ultrastructure, and pathophysiology.

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    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.

  3. Agreement between clinical history method, Orbscan IIz, and Pentacam in estimating corneal power after myopic excimer laser surgery.

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    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.

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

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    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.

  5. Development and numerical solution of a mechanistic model for corneal tissue ablation with the 193 nm argon fluoride excimer laser

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    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.

  6. 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.

  7. The Antifibrosis Effects of Peroxisome Proliferator-Activated Receptor δ on Rat Corneal Wound Healing after Excimer Laser Keratectomy

    Directory of Open Access Journals (Sweden)

    Yun Gu

    2014-01-01

    Full Text Available Corneal stromal fibrosis characterized by myofibroblasts and abnormal extracellular matrix (ECM is usually the result of inappropriate wound healing. The present study tested the hypothesis that the ligand activation of peroxisome proliferator-activated receptor (PPAR δ had antifibrosis effects in a rat model of corneal damage. Adult Sprague-Dawley rats underwent bilateral phototherapeutic keratectomy (PTK. The eyes were randomized into four groups: PBS, GW501516 (a selective agonist of PPARδ, GSK3787 (a selective antagonist of PPARδ, or GW501516 combined with GSK3787. The agents were subconjunctivally administered twice a week until sacrifice. The cellular aspects of corneal wound healing were evaluated with in vivo confocal imaging and postmortem histology. A myofibroblast marker (α-smooth muscle actin and ECM production (fibronectin, collagen type III and collagen type I were examined by immunohistochemistry and RT-PCR. At the early stages of wound healing, GW501516 inhibited reepithelialization and promoted angiogenesis. During the remodeling phase of wound healing, GW501516 attenuated the activation and proliferation of keratocytes, which could be reversed by GSK3787. GW501516 decreased transdifferentiation from keratocytes into myofibroblasts, ECM synthesis, and corneal haze. These results demonstrate that GW501516 controls corneal fibrosis and suggest that PPARδ may potentially serve as a therapeutic target for treating corneal scars.

  8. (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 ...

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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

  16. 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.

  17. 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

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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...

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  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. 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. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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

  12. 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

  13. 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)

  14. 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.

  15. 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.

  16. [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

  17. 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.

  18. 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.

  19. 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.)

  20. 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

  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. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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...

  7. 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

  8. 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.

  9. 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.

  10. 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...

  11. 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.

  12. 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.

  13. 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 ...

  14. 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.

  15. 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

  16. 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.

  17. 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.

  18. 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.

  19. 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

  20. 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

  1. 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

  2. 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

  3. 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...

  4. 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.

  5. 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

  6. 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...

  7. 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%.

  8. 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.

  9. 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.

  10. 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...

  11. 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.

  12. Corneal topography.

    Science.gov (United States)

    Seitz, B; Behrens, A; Langenbucher, A

    1997-08-01

    In the review period, limitations of individual Placido disk-based topography systems have been studied and new principles, such as raster photogrammetry, pancorneal slit topography, laser holographic interferometry, and confocal laser scanning topography, have been introduced for laboratory or clinical work. Both Fourier analysis and Zernike decomposition of topographic height data seem to be powerful new tools for cross-sectional analysis of complex topographic corneal images, such as after cataract surgery, penetrating keratoplasty, and refractive surgery, as well as for longitudinal studies of corneal changes, such as in schoolchildren. Subdividing into rational optical components may improve consistency and standardization of topography data from different systems. Topography-based flying-spot-mode excimer laser photoablation after Zernike decomposition of topography height data has been proposed for correction of irregular corneal astigmatism. Topography-based central power measurements are of increasing value for intraocular lens power calculation before cataract surgery in eyes with irregular corneal surfaces, such as in keratoconus or after refractive surgery procedures. Quantitative and qualitative classification of corneal topography maps after corneal transplantation following conventional mechanical and nonmechanical trephination or after refractive surgery may lead to a better understanding of impaired visual acuity despite a clear graft or despite significantly reduced ametropia or corneal astigmatism.

  13. 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.

  14. 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.

  15. Femtosecond laser's application in the corneal surgery

    Directory of Open Access Journals (Sweden)

    Shu-Liang Wang

    2015-10-01

    Full Text Available With the rapid development over the past two decades,femtosecond(10-15slasers(FShas become a new application in ophthalmic surgery. As laser power is defined as energy delivered per unit time, decreasing the pulse duration to femtosecond level(100fsnot only increases the power delivered but also decreases the fluence threshold for laser induced optical breakdown. In ablating tissue, FS has an edge over nanosecond lasers as there is minimal collateral damage from shock waves and heat conduction during surgical ablation. Thus, application of FS has been widely spread, from flap creation for laser-assisted in situ keratomileusis(LASIKsurgery, cutting of donor and recipient corneas in keratoplasty, creation of pockets for intracorneal ring implantation. FS applied in keratoplasty is mainly used in making graft and recipient bed, and can exactly cut different tissue of keratopathy. FS can also cut partial tissue of cornea, even if it is under the moderate corneal macula and corneal edema condition.

  16. 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...

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. [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

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. [Use of the confocal laser scanning method for determining corneal topography and corneal tissue effects in refractive corneal surgery].

    Science.gov (United States)

    Koop, N; Brinkmann, R; Schirner, G

    1996-06-01

    Refraction of the cornea head been generally measured with ophthalmometers or computer disk keratometers. We therefore used a confocal laser scanning system for measurement of the corneal topography. Enucleated tonicized pig eyes were measured before and after laser thermokeratoplasty (LTK). The topographical data were used to determine refraction and refractive change; the data were stored digitally. The single images and their differences were displayed on a PC. Unlike conventional ophthalmometry, confocal laser scanning can demonstrate the topographical shape, showing the overall topography of the cornea and local corneal effects, e.g., coagulation, mechanical lesions or high-energy laser effects. Topographical laser scanning has proven to be a generally useful method of determining refraction and surface alterations in corneal refractive surgery.

  7. 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...

  8. Past and present of corneal refractive surgery

    DEFF Research Database (Denmark)

    Vestergaard, Anders Højslet

    Surgical correction of refractive errors is becoming increasingly popular. In the 1990s, the excimer laser revolutionized the field of corneal refractive surgery with PRK and LASIK, and lately refractive lenticule extraction (ReLEx) of intracorneal tissue, using only a femtosecond laser, has become...

  9. 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.

  10. 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.

  11. 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

  12. 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.

  13. Laser-induced corneal cross-linking upon photorefractive ablation with riboflavin.

    Science.gov (United States)

    Kornilovskiy, Igor M; Kasimov, Elmar M; Sultanova, Ayten I; Burtsev, Alexander A

    2016-01-01

    To estimate the biomechanical effect of the laser-induced cross-linking resulting from photorefractive ablation of the cornea with riboflavin. Excimer laser ablation studies were performed ex vivo (32 eyes of 16 rabbits) by phototherapeutic keratectomy (PTK) and in vivo (24 eyes of 12 rabbits) by transepithelial photorefractive keratectomy (TransPRK), with and without riboflavin saturation of the stroma. Then, we performed corneal optical coherence tomography on 36 eyes of 18 patients with varying degrees of myopia at different times after the TransPRK was performed with riboflavin saturation of the stroma. Biomechanical testing of corneal samples saturated with riboflavin revealed cross-linking effect accompanied by the increase in tensile strength and maximum strength. PTK showed increase in tensile strength from 5.1±1.4 to 7.2±1.6 MPa (P=0.001), while Trans-PRK showed increase in tensile strength from 8.8±0.9 to 12.8±1.3 MPa (P=0.0004). Maximum strength increased from 8.7±2.5 to 12.0±2.8 N (P=0.005) in PTK and from 12.8±1.6 to 18.3±1.2 N (P=0.0004) in TransPRK. Clinical optical coherence tomography studies of the biomicroscopic transparent cornea at different times after TransPRK showed increased density in the surface layers of the stroma and membrane-like structure beneath the epithelium. Photorefractive ablation of the preliminary corneal stroma saturation with riboflavin causes the effect of laser-induced cross-linking, which is attended with an increase in corneal tensile strength, maximum strength, increased density in the surface layers of the stroma, and formation of a membrane-like structure beneath the epithelium after TransPRK.

  14. 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.

  15. 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

  16. 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

  17. 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.

  18. 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 ...

  19. Corneal and skin laser exposures from 1540-nm laser pulses

    Science.gov (United States)

    Johnson, Thomas E.; Mitchell, Michael A.; Rico, Pedro J.; Fletcher, David J.; Eurell, Thomas E.; Roach, William P.

    2000-06-01

    Mechanisms of tissue damage are investigated for skin and cornea exposures from 1540 nm ('eye safe') laser single pulses of 0.8 milli-seconds. New skin model data point out the advantages of using the Yucatan mini-pig versus the Yorkshire pig for in-vivo skin laser exposures. Major advantages found include similarities in thickness and melanin content when compared with human skin. Histology from Yucatan mini-pig skin exposures and the calculation of an initial ED50 threshold indicate that the main photon tissue interaction may not be solely due to water absorption. In-vitro corneal equivalents compared well with in-vivo rabbit cornea exposure under similar laser conditions. In-vivo and in-vitro histology show that initial energy deposition leading to damage occurs intrastromally, while epithelial cells show no direct injury due to laser light absorption.

  20. Preliminary studies of rabbit corneal structure using laser beams

    Science.gov (United States)

    Carstocea, Benone D.; Gafencu, Otilia L.; Apostol, Silvia; Ionita, Marcel A.; Pascu, Mihail-Lucian; Moise, N.; Popescu, Gheorghe; Roman, Miruna; Hogiu, S.

    1996-12-01

    A new method for corneal structure investigation is reported. The light reflected form rabbit cornea is recorded by a video-camera so that the images of epithelium and endothelium are obtained. Because of the great magnification factor due to the corneal curvature, the characteristics of the cells can be directly visualized. The theoretical evaluation of the optical magnification fits reasonably well the experimental results for collimated laser beams; therefore in the future it will be possible to determine with a good accuracy the corneal cell dimensions. Corneal diagnosis based on this method is discussed.

  1. 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.

  2. 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.

  3. 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.

  4. 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

  5. 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.

  6. 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.

  7. 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.

  8. 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.)

  9. 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

  10. Past and present of corneal refractive surgery: a retrospective study of long-term results after photorefractive keratectomy and a prospective study of refractive lenticule extraction

    National Research Council Canada - National Science Library

    Vestergaard, Anders Højslet

    2014-01-01

    Surgical correction of refractive errors is becoming increasingly popular. In the 1990s, the excimer laser revolutionized the field of corneal refractive surgery with PRK and LASIK, and lately refractive lenticule extraction (ReLEx...

  11. 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.)

  12. 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.

  13. 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.

  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. 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.

  17. 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

  18. 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

  19. 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...

  20. 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...

  1. Femtosecond laser technology in corneal refractive surgery: a review.

    Science.gov (United States)

    Kymionis, George D; Kankariya, Vardhaman P; Plaka, Argyro D; Reinstein, Dan Z

    2012-12-01

    To discuss current applications and advantages of femtosecond laser technology over traditional manual techniques and related unique complications in corneal refractive surgical procedures, including LASIK flap creation, intracorneal ring segment implantation, astigmatic keratotomy, presbyopic treatments, and intrastromal lenticule procedures. Literature review. From its first clinical use in 2001 for LASIK flap creation, femtosecond lasers have steadily made a place as the dominant flap-making technology worldwide. Newer applications are being evaluated and are increasing in their frequency of use. Femtosecond laser technology is rapidly becoming a heavily utilized tool in corneal refractive surgical procedures due to its reproducibility, safety, precision, and versatility. Copyright 2012, SLACK Incorporated.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. Laser-induced corneal cross-linking upon photorefractive ablation with riboflavin

    Directory of Open Access Journals (Sweden)

    Kornilovskiy IM

    2016-04-01

    Full Text Available Igor M Kornilovskiy,1 Elmar M Kasimov,2 Ayten I Sultanova,2 Alexander A Burtsev1 1Department of Eye Diseases, Federal State Budgetary Institution “National Pirogov Medical Surgical Centre”, Ministry of Health, Moscow, Russia; 2Department of Eye Diseases, Zarifa Aliyeva National Ophthalmology Center, Ministry of Health, Baku, Azerbaijan Aim: To estimate the biomechanical effect of the laser-induced cross-linking resulting from photorefractive ablation of the cornea with riboflavin.Methods: Excimer laser ablation studies were performed ex vivo (32 eyes of 16 rabbits by phototherapeutic keratectomy (PTK and in vivo (24 eyes of 12 rabbits by transepithelial photorefractive keratectomy (TransPRK, with and without riboflavin saturation of the stroma. Then, we performed corneal optical coherence tomography on 36 eyes of 18 patients with varying degrees of myopia at different times after the TransPRK was performed with riboflavin saturation of the stroma.Results: Biomechanical testing of corneal samples saturated with riboflavin revealed cross-linking effect accompanied by the increase in tensile strength and maximum strength. PTK showed increase in tensile strength from 5.1±1.4 to 7.2±1.6 MPa (P=0.001, while TransPRK showed increase in tensile strength from 8.8±0.9 to 12.8±1.3 MPa (P=0.0004. Maximum strength increased from 8.7±2.5 to 12.0±2.8 N (P=0.005 in PTK and from 12.8±1.6 to 18.3±1.2 N (P=0.0004 in TransPRK. Clinical optical coherence tomography studies of the biomicroscopic transparent cornea at different times after TransPRK showed increased density in the surface layers of the stroma and membrane-like structure beneath the epithelium.Conclusion: Photorefractive ablation of the preliminary corneal stroma saturation with riboflavin causes the effect of laser-induced cross-linking, which is attended with an increase in corneal tensile strength, maximum strength, increased density in the surface layers of the stroma, and formation of

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. Clinical effect of femtosecond laser assisted penetrating corneal transplantation operation

    Directory of Open Access Journals (Sweden)

    Hong-Jian Zhou

    2014-10-01

    Full Text Available AIM: To observe the clinical effect of femtosecond laser assisted penetrating keratoplasty. METHODS: Twenty-four cases(24 eyeswith corneal lesions were performed with femtosecond laser assisted penetrating keratoplasty. Preoperative and postoperative endothelial cell density and visual quality were compared.RESULTS: One week after operation, corneal grafts were clear in 21 eyes(87.5%, mild cloudy in 3 eyes(12.5%; visual acuity ≥0.5 in 18 eyes(75.0%, 0.2~0.4 in 6 eyes(25.0%. After 3mo the mean corneal astigmatism was 2.16±0.21D(range 2.25~3.09D. Compared to conventional penetrating keratoplasty which mean corneal astigmatism was average 3.67±0.38D after operation, there was significant difference between two groups(PPCONCLUSION: Femtosecond laser assisted penetrating corneal transplantation operation can improve patient's visual quality. And compared to traditional penetrating keratoplasty astigmatism decreased significantly, incision can be made in individual shape more precisely and neatly.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. Alternatives to allograft corneal transplantation.

    Science.gov (United States)

    Jhanji, Vishal; Sharma, Namrata; Agarwal, Tushar; Vajpayee, Rasik B

    2010-07-01

    Corneal transplantation is the most commonly performed solid organ transplantation in the world. Despite a glorious history of more than a 100 years, the success of conventional corneal transplantation surgery is marred by problems like graft rejection,graft infection and associated glaucoma due to long-term use of topical corticosteroids.In addition there is a dearth of donor corneal tissue in some parts of the world which subsequently adds on to the existing burden on the eye banks every year. We propose alternatives to the conventional corneal transplantation surgery for the management of corneal scarring. The potential use of alternatives to allograft corneal transplantation surgery has been described by corneal surgeons around the world. These techniques consist of nonsurgical interventions like contact lens fitting. Surgical alternatives include excimer laser phototherapeutic keratectomy, optical iridectomy, rotational autokeratoplasty and contralateral autokeratoplasty. Although these techniques are not practiced routinely, however, their appropriate utilization would clearly help the corneal surgeons to get rid of certain problems associated with allograft corneal transplantation. Careful selection of patients can yield encouraging results with the use of these alternative techniques. Visual outcomes may not be as good as after a routine keratoplasty; nevertheless, this setback is outweighed by advantages such as absence of corneal graft rejection. We also believe that the use of these techniques would at least partially resolve the issue of scarcity of donor corneal tissue in the developing world.

  2. Applications for the femtosecond laser in corneal surgery.

    Science.gov (United States)

    Slade, Stephen G

    2007-07-01

    Little has changed in how corneal surgery, particularly full-thickness penetrating keratoplasty, has been performed since the introduction of the operating microscope and microsurgery more than 40 years ago. The introduction of IntraLase Enabled Keratoplasty represents the first true advancement in corneal surgery in that time. There are numerous studies that have documented the high degree of complications seen in procedures such as penetrating keratoplasty. The advent of IntraLase Enabled Keratoplasty affords an opportunity to improve the safety and effectiveness of such procedures. Complications and visual outcomes remain an ongoing concern when it comes to managing patients following corneal surgery. The intensive postoperative follow up represents a significant undertaking for clinicians, staff and patients. Initial studies indicate that the use of the femtosecond laser in corneal surgery can simplify surgery, improve wound healing and lower levels of induced astigmatism. This review will examine the uses of the femtosecond laser in corneal surgery, as well as early results that have been reported.

  3. 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.

  4. 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...

  5. 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...

  6. 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.

  7. 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.

  8. 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

  9. 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...

  10. 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).

  11. 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.

  12. 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.

  13. 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.

  14. 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

  15. 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...

  16. 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

  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. 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.

  19. 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,

  20. Using Femtosecond Laser to Create Customized Corneal Flaps for Patients with Low and Moderate Refractive Error Differing in Corneal Thickness: e0121291

    National Research Council Canada - National Science Library

    Chi Zhang; Jingbin Che; Jianhong Yu; Linli Yu; Dan Yu; Gangping Zhao

    2015-01-01

      This study is designed to evaluate the visual outcomes, accuracy, and predictability of corneal flaps with different thicknesses created by 60-kHz femtosecond laser according to different corneal...

  1. 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

  2. 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

  3. 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.

  4. 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

  5. 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.

  6. 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...

  7. 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.

  8. A robotic platform for laser welding of corneal tissue

    Science.gov (United States)

    Rossi, Francesca; Micheletti, Filippo; Magni, Giada; Pini, Roberto; Menabuoni, Luca; Leoni, Fabio; Magnani, Bernardo

    2017-07-01

    Robotic surgery is a reality in several surgical fields, such as in gastrointestinal surgery. In ophthalmic surgery the required high spatial precision is limiting the application of robotic system, and even if several attempts have been designed in the last 10 years, only some application in retinal surgery were tested in animal models. The combination of photonics and robotics can really open new frontiers in minimally invasive surgery, improving the precision, reducing tremor, amplifying scale of motion, and automating the procedure. In this manuscript we present the preliminary results in developing a vision guided robotic platform for laser-assisted anterior eye surgery. The robotic console is composed by a robotic arm equipped with an "end effector" designed to deliver laser light to the anterior corneal surface. The main intended application is for laser welding of corneal tissue in laser assisted penetrating keratoplasty and endothelial keratoplasty. The console is equipped with an integrated vision system. The experiment originates from a clear medical demand in order to improve the efficacy of different surgical procedures: when the prototype will be optimized, other surgical areas will be included in its application, such as neurosurgery, urology and spinal surgery.

  9. Ultraprecise medical applications with ultrafast lasers: corneal surgery with femtosecond lasers

    Science.gov (United States)

    Loesel, Frieder H.; Kurtz, Ron M.; Horvath, Christopher; Sayegh, Samir I.; Mourou, Gerard A.; Bille, Josef F.; Juhasz, Tibor

    1999-02-01

    We investigated refractive corneal surgery in vivo and in vitro by intrastromal photodisruption using a compact ultrafast femtosecond laser system. Ultrashort-pulsed lasers operating in the femtosecond time regime are associated with significantly smaller and deterministic threshold energies for photodisruption, as well as reduced shock waves and smaller cavitation bubbles than the nanosecond or picosecond lasers. Our reliable all-solid-state laser system was specifically designed for real world medical applications. By scanning the 5 micron focus spot of the laser below the corneal surface, the overlapping small ablation volumes of single pulses resulted in contiguous tissue cutting and vaporization. Pulse energies were typically in the order of a few microjoules. Combination of different scanning patterns enabled us to perform corneal flap cutting, femtosecond-LASIK, and femtosecond intrastromal keratectomy in porcine, rabbit, and primate eyes. The cuts proved to be highly precise and possessed superior dissection and surface quality. Preliminary studies show consistent refractive changes in the in vivo studies. We conclude that the technology is capable to perform a variety of corneal refractive procedures at high precision, offering advantages over current mechanical and laser devices and enabling entirely new approaches for refractive surgery.

  10. 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

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. Relationship between Scanning Laser Polarimetry with Enhanced Corneal Compensation and with Variable Corneal Compensation

    Science.gov (United States)

    Kim, Kyung Hoon; Choi, Jaewan; Lee, Chang Hwan; Cho, Beom-Jin; Kook, Michael S.

    2008-01-01

    Purpose To evaluate the structure-function relationships between retinal sensitivity measured by Humphrey visual field analyzer (HVFA) and the retinal nerve fiber layer (RNFL) thickness measured by scanning laser polarimetry (SLP) with variable corneal compensation (VCC) and enhanced corneal compensation (ECC) in glaucomatous and healthy eyes. Methods Fifty-three eyes with an atypical birefringence pattern (ABP) based on SLP-VCC (28 glaucomatous eyes and 25 normal healthy eyes) were enrolled in this cross-sectional study. RNFL thickness was measured by both VCC and ECC techniques, and the visual field was examined by HVFA with 24-2 full-threshold program. The relationships between RNFL measurements in superior and inferior sectors and corresponding retinal mean sensitivity were sought globally and regionally with linear regression analysis in each group. Coefficients of the determination were calculated and compared between VCC and ECC techniques. Results In eyes with ABP, R2 values for the association between SLP parameters and retinal sensitivity were 0.06-0.16 with VCC, whereas they were 0.21-0.48 with ECC. The association of RNFL thickness with retinal sensitivity was significantly better with ECC than with VCC in 5 out of 8 regression models between SLP parameters and HVF parameters (P<0.05). Conclusions The strength of the structure-function association was higher with ECC than with VCC in eyes with ABP, which suggests that the ECC algorithm is a better approach for evaluating the structure-function relationship in eyes with ABP. PMID:18323701

  18. Effects of argon laser iridotomy on the corneal endothelium of pigmented rabbit eyes.

    Science.gov (United States)

    Youm, Jie Hyun; Heo, Jeong-Hwa; Kim, Hyo Myung; Song, Jong-Suk

    2014-02-01

    In Asian countries, laser iridotomy for the treatment of angle-closure glaucoma is a common cause of bullous keratopathy, which may be associated with a shallow anterior chamber and dark iris pigmentation in Asians. Several cases of corneal decompensation after argon laser iridotomy have been reported. In the present study, we evaluated the harmful effects of argon laser iridotomy on the corneal endothelium. Argon laser iridotomy was performed on the right eyes of pigmented rabbits. Changes in corneal thickness and endothelial cell density after laser iridotomy were evaluated. Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) was performed for assessment of corneal endothelial cell apoptosis. Combined staining with alizarin red and trypan blue, as well as a live/dead cell assay, were performed for evaluation of damage to the corneal endothelium induced by laser iridotomy. Corneal thickness did not change immediately after laser iridotomy; however, a significant increase was observed 24 hours after iridotomy (p = 0.001). The endothelial cell density of laser-treated eyes four days after laser iridotomy was significantly decreased compared with control eyes (p endothelium and corneal stroma. No endothelial trypan blue-stained cell nuclei were observed after laser iridotomy; however, several large endothelial cells with damaged membrane integrity were observed. The live/dead cell assay clearly showed a large number of dead cells stained red in several areas throughout the entire corneal button 24 hours after iridotomy. Argon laser iridotomy induces corneal endothelial cell apoptosis in pigmented rabbit eyes, resulting in decreased endothelial cell density.

  19. Corneal perforation associated with argon laser photocoagulation for a retinal tear.

    Science.gov (United States)

    Keithahn, M A; Gross, R H; Mannis, M J; Morales, R B; Morse, L S

    1997-01-01

    To report a corneal perforation during argon laser photocoagulation around a retinal tear following pneumatic retinopexy. The patient was examined and found to have a corneal perforation with pigment in the base of the wound. To help explain this phenomenon, we evaluated the ability of argon blue-green laser to create a corneal perforation in a cadaver eye. In a cadaver eye, we induced a corneal perforation with argon laser only when a pigmented substance was present on the corneal surface. We hypothesize that pigmented material such as an eyelash or mascara caught between the cornea and contact lens interface may have facilitated this rare complication. Clinicians should be wary of any pigmented substance on the surface of the cornea or ophthalmoscopic lens when performing argon laser photocoagulation.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. Efficacy and safety of femtosecond laser-assisted corneal endothelial keratoplasty: a randomized multicenter clinical trial.

    NARCIS (Netherlands)

    Cheng, Y.Y.; Schouten, J.S.A.G.; Tahzib, N.G.; Wijdh, R.J.; Pels, E.; Cleynenbreugel, H. van; Eggink, C.A.; Rijneveld, W.J.; Nuijts, R.M.

    2009-01-01

    BACKGROUND: To evaluate the efficacy and safety of femtosecond laser-assisted endothelial keratoplasty (FLEK) versus penetrating keratoplasty (PK) in patients with corneal endothelial disease. METHODS: A randomized multicenter clinical trial of 80 eyes of 80 patients with corneal endothelial disease

  5. Efficacy and Safety of Femtosecond Laser-Assisted Corneal Endothelial Keratoplasty : A Randomized Multicenter Clinical Trial

    NARCIS (Netherlands)

    Cheng, Yanny Y. Y.; Schouten, Jan S. A. G.; Tahzib, Nayyirih G.; Wijdh, Robert-Jan; Pels, Elisabeth; van Cleynenbreugel, Hugo; Eggink, Catharina A.; Rijneveld, Wilhelmina J.; Nuijts, Rudy M. M. A.

    2009-01-01

    Background. To evaluate the efficacy and safety of femtosecond laser-assisted endothelial keratoplasty (FLEK) versus penetrating keratoplasty (PK) in patients with corneal endothelial disease. Methods. A randomized multicenter clinical trial of 80 eyes of 80 patients with corneal endothelial disease

  6. 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.

  7. 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.

  8. 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.

  9. Multifocal intraocular lens implantation after previous corneal refractive laser surgery for myopia

    NARCIS (Netherlands)

    Vrijman, Violette; van der Linden, Jan Willem; van der Meulen, Ivanka J. E.; Mourits, Maarten P.; Lapid-Gortzak, Ruth

    2017-01-01

    Purpose: To describe the refraction and visual acuity outcomes of multifocal intraocular lens (IOL) implantation in patients with previous corneal refractive laser surgery for myopia. Setting: Academic Medical Center, University of Amsterdam, Amsterdam, and Retina Total Eye Care, Driebergen, the

  10. 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.

  11. 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

  12. Thermal and infrared-diode laser effects on indocyanine-green-treated corneal collagen

    Science.gov (United States)

    Timberlake, George T.; Patmore, Ann; Shallal, Assaad; McHugh, Dominic; Marshall, John

    1993-07-01

    It has been suggested that laser welds of collagenous tissues form by interdigitation and chemical bonding of thermally 'unraveled' collagen fibrils. We investigated this proposal by attempting to weld highly collagenous, avascular corneal tissue with an infrared (IR) diode laser as follows. First, the temperature at which corneal collagen shrinks and collagen fibrils 'split' into subfibrillary components was determined. Second, since use of a near-IR laser wavelength necessitated addition of an absorbing dye (indocyanine green (ICG) to the cornea, we measured absorption spectra of ICG-treated tissue to ensure that peak ICG absorbance did not change markedly when ICG was present in the cornea. Third, using gel electrophoresis of thermally altered corneal collagen, we searched for covalently crosslinked compounds predicted by the proposed welding mechanism. Finally, we attempted to weld partial thickness corneal incisions infused with ICG. Principal experimental findings were as follows: (1) Human corneal (type I) collagen splits into subfibrillary components at approximately 63 degree(s)C, the same temperature that produces collagen shrinkage. (2) Peak ICG absorption does not change significantly in corneal stroma or with laser heating. (3) No evidence was found for the formation of novel compounds or the loss of proteins as a result of tissue heating. All tissue treated with ICG, however, exhibited a novel 244 kD protein band indicating chemical activity between collagen and corneal stromal components. (4) Laser welding corneal incisions was unsuccessful possibly due to shrinkage of the sides of the incision, lack of incision compression during heating, or a less than optimal combination of ICG concentration and radiant exposure. In summary, these experiments demonstrate the biochemical and morphological complexity of ICG-enhanced IR laser-tissue welding and the need for further investigation of laser welding mechanisms.

  13. 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.

  14. 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.

  15. 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.)

  16. Corneal biomechanical properties after femtosecond laser assisted LASIK with the corneal visualization Scheimpflug technology and ocular response analyzer

    Directory of Open Access Journals (Sweden)

    Jing Li

    2017-02-01

    Full Text Available AIM: To investigate the changes of corneal biomechanical properties before and after femtosecond laser assisted LASIK(FS-LASIKusing Corneal Visualisation Scheimpflug Technology(Corvis STand Ocular Response Analyzer(ORA, and the correlation with other myopic parameters. METHODS:Sixty three patients(63 eyeswho had myopic femtosecond laser assisted LASIK(FS-LASIKwere enrolled in the study. The right eye of each patient was analyzed in this study. The corneal biomechanical parameters pre-operative and 1mo post-operative was measured with the Corvis ST(Oculus, Wetzlar, Germanyand ORA(Reichert, Buffalo, New York, USA. Comparison of the biomechanical property values before and after surgery was peformed using Paired t-test or Mann-Whitney U. Pearson or Spearman correlations were used to evaluate the relationship between parameters.RESULTS: The postoperative 1st A-time, Vin, 2nd A length, Vout, HC time and Radius demonstrate significant decreases comparing with preoperative values(P=0.00, P=0.00, P=0.00, P=0.00, P=0.00, P=0.00 respectively. The postoperative 2nd A-time, DA and PD significantly increases(P=0.00, P=0.00, P=0.00, however, the 1st A length had no significant difference after surgery. The CH and CRF were significantly lower after FS-LASIK(P=0.00, P=0.00. A statistically significant correlation coefficient was found between preoperative central corneal thickness(CCTwith postoperative-preoperative changes of 1st A-time, 2nd A-time, DA and Radius respectively(P=0.01, P=0.04, P=0.03, P=0.01. CONCLUSION:There were significantly changes of corneal biomechanical properties after FS-LASIK surgery. The changes of corneal biomechanical properties after FS-LASIK can be reflected by some parameters of Corvis ST and ORA. The mainly influence of corneal biomechanical alteration was possibly correlation with corneal thickness.

  17. 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

  18. 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.

  19. 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

  20. Femtosecond laser-assisted sutureless anterior lamellar keratoplasty for superficial corneal opacities.

    Science.gov (United States)

    Jabbarvand, Mahmoud; Hashemian, Hesam; Khodaparast, Mehdi; Ghadimi, Hadi; Khalilipour, Elias

    2014-11-01

    To evaluate the visual and refractive outcomes, endothelial cell count (ECC), ocular surface changes, corneal aberrations, and biomechanical profile changes after femtosecond laser-assisted anterior lamellar keratoplasty surgery for superficial corneal scars. Farabi Eye Hospital, Tehran University of Medical Sciences, Tehran, Iran. Prospective case series. Patients with superficial corneal scars had femtosecond laser-assisted anterior lamellar keratoplasty. Visual and refractive results, ECC, ocular surface changes, corneal aberrations, and biomechanical profiles were assessed preoperatively and for 1 year postoperatively. Nineteen eyes (19 patients) were evaluated. A significant decline occurred in refractive astigmatism and corneal astigmatism after 1 year. There was a nonsignificant reduction in corneal hysteresis and the corneal resistance factor from preoperatively to 1 year postoperatively. The corneal-compensated intraocular pressure (IOP) and Goldmann-correlated IOP increased during the follow-up; the increase was not significant. A statistically insignificant reduction in the root mean square for trefoil and spherical aberrations occurred between 1 month and 1 year postoperatively (P=.1 and P=.4, respectively). The decreases in primary coma and total higher-order aberrations approached significance (P=.08 and P=.07, respectively). There were no significant changes in the central corneal thickness, ECC, or ocular surface parameters. No intraoperative complications occurred. Femtosecond laser-assisted anterior lamellar keratoplasty was an efficient and safe procedure for improving the quality of vision in patients with anterior corneal pathology, and the results remained stable during the 1-year follow-up. 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.

  1. [Tissular and mechanical effects observed with an experimental femtosecond laser microkeratome for corneal refractive surgery].

    Science.gov (United States)

    Touboul, D; Salin, F; Mortemousque, B; Courjaud, A; Chabassier, P; Mottay, E; Léger, F; Colin, J

    2005-03-01

    Despite progress in mechanical microkeratomes used in refractive surgery, mechanical complications during cutting of the cornea still occur. Cutting by laser could reduce these complications and to date, the femtosecond laser is the only potential candidate for this purpose. Our study reports preliminary results with a femtosecond microkeratome for cutting porcine corneas ex vivo. We first examined the fundamental principles of the interaction between the femtosecond laser and the corneal stroma, including the volume of tissue lesions, the laser breakdown threshold of the stroma and the laser ablation selectivity. We then analyzed the quality of cutting corneal flaps with the laser, focusing on collateral tissue effects and the roughness of the interfaces observed both histologically and with scanning electron microscopy. The photoablative and photodisruptive effects were very similar with the femtosecond laser. This characteristic is specific to ultrashort impulsion photodisruptor lasers and allows for a very precise surgical procedure. The laser-induced breakdown threshold of porcine corneal stroma was found to be 0.55 J/cm2. Collateral tissue lesions were on the submicrometer level. The roughness of the stromal bed was optimal for postage stamp cutting, providing very many contiguous points of impact which were as spherical as possible. Corneal photodisruption with a femtosecond laser is reproducible and extremely accurate. The optomechanical parameters involved with this technique require great technological skill and should be placed in experienced hands.

  2. 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.

  3. 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.

  4. Effect of corneal collagen crosslinking on femtosecond laser channel creation for intrastromal corneal ring segment implantation in keratoconus.

    Science.gov (United States)

    El-Raggal, Tamer M

    2011-04-01

    To evaluate the effect of collagen crosslinking (CXL) on femtosecond laser channel creation for intrastromal corneal ring segments (ICRS) in keratoconic eyes. Magrabi Eye Hospital, Cairo, Egypt. Comparative case series. Eyes with grade II or III keratoconus were treated by CXL. After 6 months, channel creation was performed using an IntraLase FS-60 femtosecond laser. The eyes were randomly divided into 3 groups. The default femtosecond machine power setting was 1.5 mJ in Group 1, 1.6 mJ in Group 2, and 1.7 mJ in Group 3. A control group included virgin noncrosslinked keratoconic eyes in which the default power setting was 1.5 mJ. The degree of difficulty of ICRS insertion was judged subjectively. The degree of postoperative corneal haze was recorded. Fifteen eyes of 11 patients had CXL. Each group, including the control, comprised 5 eyes. After CXL, intracorneal channel creation using the 1.5 mJ default femtosecond power setting was incomplete and mechanical dissection was required to complete the channel. When the power setting was increased to 1.6 mJ or 1.7 mJ, channel creation could be completed; however, this increased the corneal reaction (haze) postoperatively. The corneal haze resolved in all eyes within 6 weeks, and there were no further complications. Femtosecond laser channel creation can be performed after CXL; however, the laser power must be modified. Results show channel dissection and ICRS implantation should be performed before or concurrent with CXL. The author has no financial or proprietary interest in any material or method mentioned. Copyright © 2011 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  5. Femtosecond laser-assisted keratoplasty in a child with corneal opacity:case report

    Directory of Open Access Journals (Sweden)

    E. Yu. Markova

    2014-07-01

    Full Text Available Corneal opacities are the fourth cause of blindness world-wide. Over the past two centuries, various corneal transplantation (i.e., keratoplasty methods have been developed and improved. Nowadays, femtolaserssisted keratoplasty is one of most promising techniques. Femtosecond laser have several advantages that provide additional surgical benefits. Among them, no thermal injury, the ability to cut deeply on a single plane and to perform various corneal profiles should be mentioned. In children, corneal disorders are of special importance while femtosecondassisted keraatoplasty case reports are rare. Here, we describe femtosecond laserssisted penetrating keratoplasty in a girl with a rough central corneal opacity.

  6. Femtosecond laser-assisted keratoplasty in a child with corneal opacity:case report

    Directory of Open Access Journals (Sweden)

    E. Yu. Markova

    2014-01-01

    Full Text Available Corneal opacities are the fourth cause of blindness world-wide. Over the past two centuries, various corneal transplantation (i.e., keratoplasty methods have been developed and improved. Nowadays, femtolaserssisted keratoplasty is one of most promising techniques. Femtosecond laser have several advantages that provide additional surgical benefits. Among them, no thermal injury, the ability to cut deeply on a single plane and to perform various corneal profiles should be mentioned. In children, corneal disorders are of special importance while femtosecondassisted keraatoplasty case reports are rare. Here, we describe femtosecond laserssisted penetrating keratoplasty in a girl with a rough central corneal opacity.

  7. 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.

  8. [Femtosecond laser for refractive corneal surgery: foundations, mode of action and clinical applications].

    Science.gov (United States)

    Mrochen, M; Donges, A; Korn, G

    2006-12-01

    Modern corneal laser surgery for the correction of optical errors of the eye requires a precise, reliable and reproducible creation of corneal lenticels (flaps). The use of ultra-short laser pulses with pulse durations of a few 100 femtoseconds (10(-13) s) allows for non-thermal cuts of ocular tissue. Mean flap thicknesses as small as 100 microm with a reproducibility of 10 microm (standard deviation) can be created by using mechano-optical adaptations through the eye. Thus, the femtosecond laser can be considered a good alternative approach with a safety in clinical use that is comparable with that of mechanical microkeratomes.

  9. Corneal refractive surgery using an ultraviolet (213 nm) solid state laser

    Science.gov (United States)

    Ren, Qiushi; Gailitis, Raymond P.; Thompson, Keith P.; Penney, Carl M.; Lin, Jui T.; Waring, George O., III

    1991-06-01

    The authors demonstrate the use of a frequency multiplied Q-switched Nd:YAG laser to generate the fifth (213 nm) and the fourth (266 nm) harmonic frequencies to ablate porcine corneas and synthetic collagen materials. This new strategy is discussed for corneal refractive surgery using a solid state laser. The potential for spatially resolved refractive correction based on a 213 nm solid state laser is reviewed in light of new corneal imaging technology that can detect localized refractive errors of the eye. Finally, the authors discuss remaining problems that need to be addressed before this technology can be applied to clinical investigation.

  10. 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.

  11. 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.

  12. Simultaneous topography-guided PRK followed by corneal collagen cross-linking after lamellar keratoplasty for keratoconus

    Directory of Open Access Journals (Sweden)

    Spadea L

    2012-11-01

    Full Text Available Leopoldo Spadea,1 Marino Paroli21University of L’Aquila, Department of Biotechnological and Applied Clinical Sciences, Eye Clinic, L’Aquila, 2La Sapienza University, Department of Biotechnology and Medical-Surgical Sciences, Latina, ItalyBackground: The purpose of this paper is to report the results of using combined treatment of customized excimer laser-assisted photorefractive keratectomy (PRK and prophylactic corneal collagen crosslinking (CXL for residual refractive error in a group of patients who had previously undergone lamellar keratoplasty for keratoconus.Methods: The study included 14 eyes from 14 patients who had originally been treated for keratoconus in one eye by excimer laser-assisted lamellar keratoplasty (ELLK, and subsequently presented with residual ametropia (-6.11 D ± 2.48, range -2.50 to -9.50. After a mean 40.1 ± 12.4 months since ELLK they underwent combined simultaneous corneal regularization treatment with topographically guided transepithelial excimer laser PRK (central corneal regularization and corneal CXL induced by riboflavin-ultraviolet A.Results: After a mean 15 ± 6.5 (range 6–24 months, all eyes gained at least one Snellen line of uncorrected distance visual acuity (range 1–10. No patient lost lines of corrected distance visual acuity, and four patients gained three lines of corrected distance visual acuity. Mean manifest refractive spherical equivalent was -0.79 ± 2.09 (range +1 to -3.0 D, and topographic keratometric astigmatism was 5.02 ± 2.93 (range 0.8–8.9 D. All the corneas remained clear (haze < 1.Conclusion: The combination of customized PRK and corneal CXL provided safe and effective results in the management of corneal regularization for refractive purposes after ELLK for keratoconus.Keywords: corneal collagen crosslinking, excimer laser-assisted lamellar keratoplasty, photorefractive keratectomy

  13. 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.

  14. Application of corneal tomography before keratorefractive procedure for laser vision correction.

    Science.gov (United States)

    Luz, Allan; Lopes, Bernardo; Salomão, Marcela; Ambrósio, Renato

    2016-05-01

    Ectasia after refractive surgery represents a major concern among refractive surgeons. Corneal abnormalities and preexisting corneal ectasia are the most important risk factors. Corneal topography and central corneal thickness are the factors traditionally screening for in refractive surgery candidates. Study of the anterior surface by Placido topography allows for identification of keratoconus before biomicroscopy. However, this is insufficient for the evaluation of pre-operative refractive surgery. There are cases of ectasia after laser in situ keratomilusis (LASIK) without identifiable risk factors such that there is a need to go beyond the corneal surface. A key requirement is quantifying susceptibility to corneal biomechanical instability and progression to ectasia. Tomographic indices derived from elevation maps and pachymetry spatial variation produce a Belin Ambrosio display final D index (BAD-D index), which has shown better results compared to surface curvature indices for detecting very mild forms of ectasia. A logistic regression formula, integrating age, residual stromal bed, and BAD-D (Ectasia Susceptibility Score, ESS) resulted in a significant improvement in accuracy, leading to 100% sensitivity and 94% specificity for detecting susceptible cases. A comprehensive corneal structural analysis based on corneal segmental tomography can detect susceptible corneas, which increases safety for refractive surgery patients. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Cooling prevents induction of corneal damage by argon laser peripheral iridotomy.

    Science.gov (United States)

    Kataoka, Takuya; Zako, Masahiro; Takeyama, Masayuki; Ohno-Jinno, Akiko; Sugenoya, Junichi; Iwaki, Masayoshi

    2007-01-01

    There are many reports of corneal complications caused by argon laser peripheral iridotomy. In this study, we investigated whether cooling the anterior ocular segment during laser iridotomy prevented corneal damage. A space for cooling the anterior ocular segment by perfusion with ice-cold water was made between the cornea and a contact lens. Dutch pigmented rabbits were excessively irradiated by an argon green laser, aiming at the peripheral iris. We used a contact lens without a cooling system as a control. Temperature in the anterior chamber and intraocular pressure were also monitored throughout the experiment. During laser treatment, the temperature without the cooling system rose to a maximum of 44.5 degrees C in the anterior chamber, whereas use of the cooling system consistently kept this temperature at 11.1 degrees -16.1 degrees C. Although most eyes treated without cooling showed corneal damage, damage was seen in only a few or in no eyes cooled during laser treatment. Argon laser treatment using contact lenses with a cooling system drastically reduced the corneal damage induced by argon laser peripheral iridotomy. This technique may be acceptable for clinical use, considering its technical simplicity and low incidence of treatment-related complications.

  16. 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.

  17. Designing multifocal corneal models to correct presbyopia by laser ablation

    Science.gov (United States)

    Alarcón, Aixa; Anera, Rosario G.; Del Barco, Luis Jiménez; Jiménez, José R.

    2012-01-01

    Two multifocal corneal models and an aspheric model designed to correct presbyopia by corneal photoablation were evaluated. The design of each model was optimized to achieve the best visual quality possible for both near and distance vision. In addition, we evaluated the effect of myosis and pupil decentration on visual quality. The corrected model with the central zone for near vision provides better results since it requires less ablated corneal surface area, permits higher addition values, presents stabler visual quality with pupil-size variations and lower high-order aberrations.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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...

  3. 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.

  4. 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

  5. Human cadaver retina model for retinal heating during corneal surgery with a femtosecond laser

    Science.gov (United States)

    Sun, Hui; Fan, Zhongwei; Yun, Jin; Zhao, Tianzhuo; Yan, Ying; Kurtz, Ron M.; Juhasz, Tibor

    2014-02-01

    Femtosecond lasers are widely used in everyday clinical procedures to perform minimally invasive corneal refractive surgery. The intralase femtosecond laser (AMO Corp. Santa Ana, CA) is a common example of such a laser. In the present study a numerical simulation was developed to quantify the temperature rise in the retina during femtosecond intracorneal surgery. Also, ex-vivo retinal heating due to laser irradiation was measured with an infrared thermal camera (Fluke Corp. Everett, WA) as a validation of the simulation. A computer simulation was developed using Comsol Multiphysics to calculate the temperature rise in the cadaver retina during femtosecond laser corneal surgery. The simulation showed a temperature rise of less than 0.3 degrees for realistic pulse energies for the various repetition rates. Human cadaver retinas were irradiated with a 150 kHz Intralase femtosecond laser and the temperature rise was measured withan infrared thermal camera. Thermal camera measurements are in agreement with the simulation. During routine femtosecond laser corneal surgery with normal clinical parameters, the temperature rise is well beneath the threshold for retina damage. The simulation predictions are in agreement with thermal measurements providing a level of experimental validation.

  6. 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)

  7. 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.

  8. Refractive surgery following corneal graft.

    Science.gov (United States)

    Alió, Jorge L; Abdou, Ahmed A; Abdelghany, Ahmed A; Zein, Ghassam

    2015-07-01

    To review the different surgical procedures for management of postkeratoplasty refractive errors after total suture removal. There are different surgical options to address residual refractive errors that frequently occur after corneal transplantation. The correction can be done on the corneal surface or intraocular with intraocular lens (IOL) implantation which requires complete tectonic and refractive stability after suture removal. The most commonly used procedures are photorefractive keratectomy, laser in-situ keratomileusis and Phakic IOLs. Keratoplasty has been profited by recent advances in refractive surgery. Custom excimer laser ablation is an alternative way to treat irregular errors. New IOL modalities are good practical options for a wide range of errors. Femtosecond laser, as a new option in the toolbox, can modify corneal grafting refractive results and assist corrective refractive procedures. Although being the most successful organ transplantation, keratoplasty is usually followed by significant ametropia. Different corrective modalities exist and the choice should fit ocular conditions, patient requirements, surgeon skills and the available technologies. Recent advances in ophthalmic surgery have improved the outcomes.

  9. The evolution of corneal and refractive surgery with the femtosecond laser

    National Research Council Canada - National Science Library

    Aristeidou, Antonis; Taniguchi, Elise V; Tsatsos, Michael; Muller, Rodrigo; McAlinden, Colm; Pineda, Roberto; Paschalis, Eleftherios I

    2015-01-01

    .... As we witness the transition from femto-LASIK to femto-cataract surgery it becomes obvious that this innovation is here to stay. This article presents some of the most relevant advances of femtosecond lasers to modern corneal and refractive surgery.

  10. 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.

  11. 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.

  12. 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.)

  13. 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.

  14. 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.

  15. 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

  16. 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

  17. 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

  18. 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

  19. 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.

  20. 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.

  1. 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.

  2. Influence of the flap on outcomes in corneal refractive surgery with femtosecond laser: SMILE vs. FLEx.

    Science.gov (United States)

    Alió, J L; El Bahrawy, M; Angelov, A; Ortiz, D; Yébana, P

    2017-05-01

    To investigate the influence of creating a flap on the postoperative optical quality of the cornea in terms of predicted corneal curvature and Seidel aberrations after 2 modalities of femtosecond assisted corneal lenticule extraction laser for the correction of myopia and myopic astigmatism: The flapless procedure small incision lenticular extraction (SMILE) and the flap-based femtosecond lenticular extraction (FLEx). The study is a prospective consecutive non-randomised comparative interventional case series including 64 eyes with myopic or myopic astigmatism refractive errors. Patients were divided into 2 groups matched for age, sex and myopia. One group underwent SMILE treatment and the other underwent FLEx treatment. Seidel aberrations root-mean-square values were obtained with a 10mm aperture using the ATLAS 9000 topographer before surgery and 3 months after surgery. The relationship between the post-surgical corneal radius and the predicted sculpted radius were analysed in each group. The mean percentage change in the curvature radius was -2.03% in the FLEx group and -1.77% in the SMILE group (P=.655). The higher correlation for the SMILE group demonstrates a better predictability after the surgery. As regards corneal aberrations, the FLEx treatment showed a greater increase of higher order aberrations than SMILE treatment (P=.04). The mean refractive change in corneal curvature, which is indirectly related to the biomechanical response of the corneal surface after the lenticule cut and extraction, was similar after both treatments. However, the flap based FLEx procedure showed a greater degradation of the corneal optical quality in terms of induction of higher order aberrations. Copyright © 2016 Sociedad Española de Oftalmología. Publicado por Elsevier España, S.L.U. All rights reserved.

  3. [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

  4. A new technology for applanation free corneal trephination: the picosecond infrared laser (PIRL).

    Science.gov (United States)

    Linke, Stephan J; Frings, Andreas; Ren, Ling; Gomolka, Amadeus; Schumacher, Udo; Reimer, Rudolph; Hansen, Nils-Owe; Jowett, Nathan; Richard, Gisbert; Miller, R J Dwayne

    2015-01-01

    The impact of using a Femtosecond laser on final functional results of penetrating keratoplasty is low. The corneal incisions presented here result from laser ablations with ultrafast desorption by impulsive vibrational excitation (DIVE). The results of the current study are based on the first proof-of-principle experiments using a mobile, newly introduced picosecond infrared laser system, and indicate that wavelengths in the mid-infrared range centered at 3 μm are efficient for obtaining applanation-free deep cuts on porcine corneas.

  5. 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.

  6. Apparent Corneal Ectasia After Bilateral Intrastromal Femtosecond Laser Treatment for Presbyopia.

    Science.gov (United States)

    Dukic, Adrijana; Bohac, Maja; Pasalic, Adi; Koncarevic, Mateja; Anticic, Marija; Patel, Sudi

    2016-11-01

    To report a case of apparent corneal ectasia after intrastromal femtosecond laser treatment for presbyopia (INTRACOR). A healthy 56-year-old male with low hyperopia underwent an unremarkable bilateral INTRACOR procedure in March/April 2011. The patient was discharged after follow-up and returned 5 years later. Before discharge, the monocular logarithm of the minimal angle of resolution uncorrected distance visual acuity (UDVA) values were R, 0.0 and L, 0.10. In both eyes near (UNVA) visual acuities were 0.0. There were signs of slight posterior central corneal steepening without loss of corneal stability. Five years postop, monocular UDVA and UNVA values were 0.4 and 0.0, respectively. Ectasia was observed in both eyes, and the centrally placed 5 concentric rings after the INTRACOR procedure were visible under slit-lamp biomicroscopy. There is no clear reason to explain why the patient developed bilateral corneal steepening. It could be that the patient's corneal stromal fibers gradually weakened over this 5-year period.

  7. [Studies of the development of refractive effects in intrastromal refractive corneal surgery with the picosecond laser].

    Science.gov (United States)

    Vogel, A; Günther, T; Asiyo-Vogel, M; Birngruber, R

    1997-07-01

    Picosecond laser intrastromal photorefractive keratectomy (ISPRK) aims at achieving a flattening of the central cornea by plasma-mediated tissue evaporation without affecting the anterior or posterior corneal layers. We investigated the laser-induced tissue effects to establish a functional relationship between laser parameters and tissue removal and to assess their influence on the healing process and long-term refractive changes. A modified ISL 2001 System with a cone angle of 30 degrees was used for in vitro investigations of the laser effects in water and porcine cornea. Photographic methods were used to determine the plasma volume and the thickness of the laser-generated intrastromal bubble layer as a function of the pulse energy and the number and separation in which the pulses were applied (216 eyes). Histological evaluation was done by polarization microscopy (9 eyes). Polarization microscopy revealed only minor signs of thermal tissue damage. The maximum amount of tissue that can be evaporated without damaging the outer corneal layers corresponds to a layer about 10 microns thick. With a 6-mm optical zone, this tissue removal yields an immediate refractive effect of only 0.85 dpt. Stronger long-term refractive changes observed in animal experiments and clinical studies must thus be due to the healing response of the cornea. The healing response may be induced by mechanical distortion due to intrastromal bubble formation affecting about one third of the corneal thickness. Since the refractive effects are apparently strongly influenced by corneal healing, they are poorly predictable and can probably not be used for clinical purposes.

  8. 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

  9. 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.

  10. 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.

  11. [Intraocular lens power calculations in eyes with previous corneal refractive surgery].

    Science.gov (United States)

    Liu, Hou-cang; Xie, Li-xin

    2007-02-01

    Results of intraocular lens power calculation were lower than actual required power in eyes with previous corneal refractive surgery because the inaccurate readings of corneal power obtained from standard keratometry. This causes the unacceptable hyperopia after cataract surgery. With increasing of population undergone excimer laser refractive surgery, this problem will be an obvious problem in years or decades. Several methods have been proposed to increase the accuracy of intraocular lens power calculation for cataract surgery in eyes undergone refractive surgery and are reviewed in this article.

  12. Corneal collagen cross-linking outcomes: review.

    Science.gov (United States)

    Jankov Ii, Mirko R; Jovanovic, Vesna; Delevic, Sladjana; Coskunseven, Efekan

    2011-02-11

    Keratoconus is a condition characterized by biomechanical instability of the cornea, presenting in a progressive, asymmetric and bilateral way. Corneal collagen cross-linking with riboflavin and UVA (CXL) is a new technique of corneal tissue strengthening that combines the use of riboflavin as a photo sensitizer and UVA irradiation. The studies showed that CXL was effective in halting the progression of keratoconus over a period of up to four years. The published studies also revealed a reduction of max K readings by more than 2 D, while the postoperative SEQ was reduced by an average of more than 1 D, and refractive cylinder decreased by about 1 D. No eyes lost any line of BCDVA. Moreover, there was no significant decrease in endothelial cell density. It was also found that CXL treatment was effective with reducing corneal and total wavefront aberrations. Corneal cross-linking has also led to an arrest and/or even a partial reversal of keratectasia in the treatment of iatrogenic ectasia after excimer laser ablation. A primary intervention such as CXL should be considered to potentially increase the biomechanical stability of the corneal tissue and postpone the need of lamellar or penetrating keratoplasty.

  13. 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

  14. Riboflavin-UV--a crosslinking for fixation of biosynthetic corneal collagen implants.

    Science.gov (United States)

    Wand, Kerstin; Neuhann, Raphael; Ullmann, Andrea; Plank, Katharina; Baumann, Michael; Ritter, Roland; Griffith, May; Lohmann, Chris P; Kobuch, Karin

    2015-05-01

    To evaluate riboflavin-UV-A crosslinking as an alternative suture-free fixation method for biosynthetic corneal collagen implants. A range of cell-free corneal implants consisting of recombinant human collagen type III were examined. In vitro, the implants were crosslinked with different riboflavin solutions and irradiations. Ex vivo, the biosynthetic corneal implants were placed on the anterior cornea of porcine and rabbit eyes after performing deep anterior lamellar keratoplasty with a trephine, femtosecond laser, or excimer laser. UV-A crosslinking was performed with isotonic or hypotonic riboflavin at either standard or rapid procedure. The corneas were excised, fixed in PFA 4%, and embedded in paraffin. Crosslinking effects on the implants and the adhesion between implant and corneal bed were evaluated by slit-lamp biomicroscopy, optical coherence tomography (OCT) images, and histologically. After the crosslinking procedure, the implants showed different degrees of thinning. The accuracy of cutting the corneal bed was highest with the excimer laser. Good adhesion of the implant in the corneal bed could be demonstrated in OCT images. This was more accurate in porcine eyes than in rabbit eyes. Histologically, crosslinks between implant and corneal stroma were demonstrated. There was no difference between standard and rapid crosslinking procedures. Riboflavin-UV-A crosslinking as a fixation method for biosynthetic corneal collagen implants was demonstrated to be promising. It can reduce suture-related complications such as haze formation and surface irregularity. Stability of the implants, especially shrinkage after riboflavin-UV-A crosslinking, needs to be further evaluated. Biostability, integration, and long-term outcome are further evaluated in in vivo animal experiments.

  15. [Effects of amniotic extraction on epithelial wound healing and stromal remodelling after excimer laser keratectomy in rabbit cornea].

    Science.gov (United States)

    Xiao, Qiguo; Chen, Yuan; Du, Juan; Wang, Hua; Li, Wei; Liu, Zuguo

    2014-01-01

    To investigate the effects and mechanism of amniotic extraction on corneal healing after photorefractive keratectomy (PRK). Experimental Study. Thirty-six New Zealand rabbit corneas were performed with PRK models (-10 diopters, 6.5 mm diameter). According to random number table, all eyes were divided into three groups, including treated with amniotic extraction, 0.1% dexamethasone and excipient respectively after operation. Clinical and histopathologic examinations were taken by slit-lamp microscope and light microscope. Corneal epithelium reparation was observed by fluorescent staining. Corneal stroma cell apoptosis was evaluated by terminal deoxyribonucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling (TUNEL) assay. Myofibroblast generation was evaluated by immunofluorescence checking the expression of alpha-smooth muscle actin (α-SMA). The number of TUNEL and α-SMA positive cells was analyzed to explore the effects on corneal haze. The haze grading was compared between groups using Kruskal-Wallis H test. Mean values for each experiment were compared between groups using a one-way analysis of variance and LSD-t test.Spearman rank analysis was used to evaluate the correlation between the haze grading and the expression of TUNEL positive cells and α-SMA. The corneas of seventy-two eyes reepithelialized in 6 days after operation. The average epithelium repair time of the AE group was (4.12 ± 0.62) d, the dexamethasone group was (5.25 ± 0.78) d, and the excipient group was (4.96 ± 0.73) d. The progression of reepithelialization was significantly faster in the AE group than the other two groups (F = 14.144, P healing of epithelial cell by interacting with the corneal cell factors, reducing the cell apoptosis, corneal wound healing response and rebuilding the corneal matrix with less myofibroblast, collagen and scar and finally reduce the formation of haze.

  16. Visual outcomes and safety of a refractive corneal inlay for presbyopia using femtosecond laser.

    Science.gov (United States)

    Limnopoulou, Aliki N; Bouzoukis, Dimitrios I; Kymionis, George D; Panagopoulou, Sophia I; Plainis, Sotiris; Pallikaris, Aristophanes I; Feingold, Vladimir; Pallikaris, Ioannis G

    2013-01-01

    To evaluate the outcomes and safety of a refractive inlay (Flexivue Micro-Lens, Presbia Coöperatief U.A.) for the corneal compensation of presbyopia. This prospective, interventional clinical study comprised 47 emmetropic presbyopes with a mean age of 52±4 years (range: 45 to 60 years). The inlay was inserted, centered on the line of sight, inside a corneal pocket created in the patient's nondominant eye, using a femtosecond laser. Follow-up was 12 months. Visual acuity, corneal topography, wavefront aberrometry, contrast sensitivity, structural corneal alterations, and questionnaires were evaluated. Twelve months after surgery, uncorrected near visual acuity was 20/32 or better in 75% of operated eyes, whereas mean uncorrected distance visual acuity (UDVA) of operated eyes was statistically significantly decreased from 0.06±0.09 logMAR (20/20) (range: -0.08 to 0.26) preoperatively to 0.38±0.15 logMAR (20/50) (range: 0.12 to 0.8) (Ppresbyopia in emmetropic presbyopes aged between 45 and 60 years old. Copyright 2013, SLACK Incorporated.

  17. Using laser induced breakdown spectroscopy and acoustic radiation force elasticity microscope to measure the spatial distribution of corneal elasticity

    Science.gov (United States)

    Sun, Hui; Li, Xin; Fan, Zhongwei; Kurtz, Ron; Juhasz, Tibor

    2017-02-01

    Corneal biomechanics plays an important role in determining the eye's structural integrity, optical power and the overall quality of vision. It also plays an increasingly recognized role in corneal transplant and refractive surgery, affecting the predictability, quality and stability of final visual outcome [1]. A critical limitation to increasing our understanding of how corneal biomechanics controls corneal stability and refraction is the lack of non-invasive technologies that microscopically measure local biomechanical properties, such as corneal elasticity within the 3D space. Bubble based acoustic radiation force elastic microscopy (ARFEM) introduce the opportunity to measure the inhomogeneous elastic properties of the cornea by the movement of a micron size cavitation bubble generated by a low energy femtosecond laser pulse [2, 3]. Laser induced breakdown spectroscopy (LIBS) also known as laser induced plasma spectroscopy (LIPS) or laser spark spectrometry (LSS) is an atomic emission spectroscopy [4]. The LIBS principle of operation is quite simple, although the physical processes involved in the laser matter interaction are complex and still not completely understood. In one sentence for description, the laser pulses are focused down to a target so as to generate plasma that vaporizes a small amount of material which the emitted spectrum is measured to analysis the elements of the target.

  18. Retinal nerve fiber layer measurements by scanning laser polarimetry with enhanced corneal compensation in healthy subjects.

    Science.gov (United States)

    Rao, Harsha L; Venkatesh, Chirravuri R; Vidyasagar, Kelli; Yadav, Ravi K; Addepalli, Uday K; Jude, Aarthi; Senthil, Sirisha; Garudadri, Chandra S

    2014-12-01

    To evaluate the (i) effects of biological (age and axial length) and instrument-related [typical scan score (TSS) and corneal birefringence] parameters on the retinal nerve fiber layer (RNFL) measurements and (ii) repeatability of RNFL measurements with the enhanced corneal compensation (ECC) protocol of scanning laser polarimetry (SLP) in healthy subjects. In a cross-sectional study, 140 eyes of 73 healthy subjects underwent RNFL imaging with the ECC protocol of SLP. Linear mixed modeling methods were used to evaluate the effects of age, axial length, TSS, and corneal birefringence on RNFL measurements. One randomly selected eye of 48 subjects from the cohort underwent 3 serial scans during the same session to determine the repeatability. Age significantly influenced all RNFL measurements. RNFL measurements decreased by 1 µm for every decade increase in age. TSS affected the overall average RNFL measurement (β=-0.62, P=0.003), whereas residual anterior segment retardance affected the superior quadrant measurement (β=1.14, P=0.01). Axial length and corneal birefringence measurements did not influence RNFL measurements. Repeatability, as assessed by the coefficient of variation, ranged between 1.7% for the overall average RNFL measurement and 11.4% for th nerve fiber indicator. Age significantly affected all RNFL measurements with the ECC protocol of SLP, whereas TSS and residual anterior segment retardance affected the overall average and the superior average RNFL measurements, respectively. Axial length and corneal birefringence measurements did not influence any RNFL measurements. RNFL measurements had good intrasession repeatability. These results are important while evaluating the change in structural measurements over time in glaucoma patients.

  19. Observation on ultrastructure and histopathology of cornea following femtosecond laser-assisted deep lamellar keratoplasty for acute corneal alkaline burns

    Directory of Open Access Journals (Sweden)

    Wen-Jing Li

    2016-04-01

    Full Text Available AIM: To demonstrate the changes in ultrastructure and histopathology of the cornea in acute corneal alkaline burns after femtosecond laser-assisted deep lamellar keratoplasty. METHODS: The New Zealand white rabbits treated with alkaline corneal burn were randomized into two groups, Group A (16 eyes with femtosecond laser-assisted deep lamellar keratoplasty 24h after burn and Group B (16 eyes without keratoplasty as controls. All eyes were evaluated with transmission electron microscopy (TEM at 1, 2, 3, and 4wk follow-up, then all corneas were tested by hematoxylin and eosin staining histology. RESULTS: The corneal grafts in Group A were transparent, while those in Group B showed corneal stromal edema and loosely arranged collagen fibers. One week after treatment, TEM revealed the intercellular desmosomes in the epithelial layers and intact non-dissolving nuclei in Group A. At week 4, the center of the corneas in Group A was transparent with regularly arranged collagen fibers and fibroblasts in the stroma. In Group B, squamous cells were observed on the corneal surface and some epithelial cells were detached. CONCLUSION: Femtosecond laser-assisted deep lamellar keratoplasty can suppress inflammatory responses, prevent toxic substance-induced injury to the corneal endothelium and inner tissues with quicker recovery and better visual outcomes.

  20. Analysis of low-energy and high-frequency femtosecond laser for the construction of deep anterior donor corneal lamellae

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    Gustavo Victor

    2014-04-01

    Full Text Available Purpose: To evaluate the efficacy and reliability of a low-energy femtosecond laser with a high repetition rate for construction of deep anterior donor corneal lamellae. Methods: This was a prospective laboratory investigation. Twenty-five human corneal buttons were femtosecond laser cut to create thick anterior lamellae (diameter, 10mm; thickness, 500µm. The laser cuts were made using an LDV® femtosecond laser in a Ziemer® anterior chamber. To obtain a better edge, the lamellae were trephined with an 8mm trephine (Katena®. The central corneal thickness and the anterior lamellae were measured using a Mitutoyo® thickness gauge with an accuracy of 0.001mm. Results: The central thickness of the 25 corneas ranged from 500 to 705µm (mean, 584 ± 51µm. The thickness of the anterior lamellae ranged from 420 to 480µm (mean, 455 ± 12.7µm. The anterior lamellae diameters were 7.90 ± 0.1mm, and all laser cuts were round. The lamellar interfaces appeared regular by surgical microscopy. There were no cases of inter-lamellar adhesion. Conclusion: The LDV® femtosecond laser appears to be a safe and reliable instrument for cutting deep anterior lamellae from donor corneoscleral buttons. Minimal variation in donor lamellar depth with the laser will be useful for creating donor corneal tissue for deeper anterior lamellar keratoplasty or endothelial keratoplasty surgery or both from a single donor cornea.

  1. 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

    Full Text Available OBJETIVO: Avaliar a qualidade de vida e de visão e o estresse de pacientes portadores de ametropias submetidos a procedimentos cirúrgicos. MÉTODOS: Estudo longitudinal observacional em que foram estudados 100 pacientes; 54 usuários de óculos, 21 usuários de lentes de contato interessados no procedimento cirúrgico e 25 controles usuários de óculos ou lentes de contato, mas que não desejavam ser operados no período de um ano. Os questionários aplicados foram o National Eye Institute Visual Function Questionnaire (NEI-VFQ-25 de qualidade de vida e o Self Reporting Questionnaire - SRQ-20 para avaliação da saúde mental. Os pacientes que se submeteram à cirurgia responderam aos questionários aplicados por uma observadora antes da mesma, três, seis e doze meses após a intervenção. O grupo controle respondeu de forma auto-aplicada no início do estudo, seis e doze meses após a primeira avaliação. RESULTADOS: No grupo da cirugia dos 54 pacientes que usavam óculos 39 fizeram cirurgia de ceratectomia fotorrefrativa por excimer laser(PRK e 15 fizeram ceratomileuse assistida por excimer laserin situ (LASIK e dos 21 que usavam lentes de contato 12 fizeram cirurgia de ceratectomia fotorrefrativa e nove fizeram ceratomileuse assistida por excimer laser in situ (LASIK. O grupo controle esteve estável durante os 12 meses em relação aos instrumentos aplicados. Três meses após a cirurgia o grupo da cirurgia apresentou melhora significante da qualidade de vida e de visão em relação ao pré-operatório independentemente do tipo de cirurgia realizada. Um ano após a cirurgia os índices de qualidade de vida e de saúde mental, foram semelhantes aos do grupo controle. O Self Reporting Questionnaire - SRQ 20 mostrou diminuição significante do índice de sintomas a partir dos três meses de pós-operatório. CONCLUSÃO: A qualidade de visão e de vida dos pacientes submetidos à cirurgia de correção de ametropia mudou

  2. 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.

  3. 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.

  4. Mapping of normal corneal K-structures by in vivo laser confocal microscopy.

    Science.gov (United States)

    Yokogawa, Hideaki; Kobayashi, Akira; Sugiyama, Kazuhisa

    2008-09-01

    To produce 2-dimensional reconstruction maps of normal human corneal fibrous structures beneath the Bowman layer (K-structures) by in vivo laser confocal microscopy and to show association of structures with the anterior corneal mosaic (ACM). Central corneal regions of 3 healthy volunteers were scanned. Acquired images of K-structures for each eye were arranged and mapped into a subconfluent montage. For each subject, electrical tracings of K-structures were superimposed on a slit-lamp photograph of the ACM produced by rubbing the eyelid. A mean of 677 +/- 211 images of K-structures were obtained for each eye. Mean dimensions of the mapped areas were 5.88 +/- 0.50 (horizontal) and 3.51 +/- 1.37 mm (vertical). In all subjects, K-structures formed a netlike pattern (mean area, 0.082 +/- 0.051 mm), and electrical tracings had good concordance with the ACM. This is the first study, to our knowledge, to elucidate the overall distribution of K-structures in normal human corneas. The netlike pattern of K-structures corresponded well with ACM pattern. These results support the hypothesis that the K-structures are the anterior collagen fiber bundles running at the posterior surface of the Bowman layer and thus are the structural basis for ACM formation.

  5. Corneal perforation by an astigmatic keratotomy performed with an optical coherence tomography-guided femtosecond laser.

    Science.gov (United States)

    Cherfan, Daniel G; Melki, Samir A

    2014-07-01

    We present a case of corneal perforation secondary to an intrastromal astigmatic keratotomy performed with an optical coherence tomography-guided femtosecond laser. The keratotomy was concomitant with cataract surgery and resulted in a flat anterior chamber prior to the start of lens extraction. Interrupted nylon sutures were placed to seal the keratotomy prior to phacoemulsification. Escape of cavitation bubbles into the anterior chamber or the liquid interface can alert the surgeon to the possibility of unintended perforation of the endothelium or the epithelium, respectively. Neither 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.

  6. 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.

  7. Time-resolved observations of shock waves and cavitation bubbles generated by femtosecond laser pulses in corneal tissue and water.

    Science.gov (United States)

    Juhasz, T; Kastis, G A; Suárez, C; Bor, Z; Bron, W E

    1996-01-01

    Photodisruption in ocular media with high power pulsed lasers working at non-absorbing frequencies have become a well established surgical tool since the late seventies. Shock waves and cavitation bubbles generated by the optical breakdown may strongly influence the surgical effect of photodisruptive lasers. We have investigated the shock wave and cavitation bubble effects of femtosecond laser pulses generated during photodisruption in corneal tissue and water. The results are compared to those obtained with longer laser pulses. Laser pulses with 150 fs duration at approximately 620 nm wavelength have been focused into corneal tissue and water to create optical breakdown. Time-resolved flash photography has been used to investigate the dynamics of the generated shock waves and cavitation bubbles. A rapid decay of the shock waves is observed in both materials with similar temporal characteristics and with a spatial range considerably smaller than that of shock waves induced by picosecond (or nanosecond) optical breakdown. Cavitation bubbles are observed to develop more rapidly and to reach smaller maximum diameter than those generated by longer pulses. In corneal tissue, single intrastromal cavitation bubbles generated by femtosecond pulses disappear within a few tens of seconds, notably faster than cavitation bubbles generated by picosecond pulses. The reduced shock wave and cavitation bubble effects of the femtosecond laser result in more localized tissue damage. Therefore, a more confined surgical effect should be expected from a femtosecond laser than that from picosecond (or nanosecond) lasers. This indicates a potential benefit from the applications of femtosecond laser technology to intraocular microsurgery.

  8. 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.

  9. 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

  10. Multiphoton imaging of corneal tissue with near-infrared femtosecond laser pulses: corneal optical tomography and its use in refractive surgery

    Science.gov (United States)

    Wang, Bao-Gui; Koenig, Karsten; Riemann, Iris; Schubert, Harald; Halbhuber, Karl-Juergen

    2006-02-01

    The two-photon-mediated autofluorescence and second harmonic generation (SHG) are acting as a novel diagnostic tool to perform tissue optical tomography with submicron resolution. The three-dimensional corneal ultrastructure of whole depth can be probed without any staining or mechanical slicing. Compared with photodisruptive surgical effects occurring at TW/cm2 light intensity, multiphoton imaging can be induced at MW-GW/cm2 photon intensity. The multiphoton microscopy based on nonlinear absorption of femtosecond laser pulses at the wavelength of 715-930nm emitted from solid-state Ti: sapphire system is being used as a precise non-invasive monitoring tool to determine the interest of region, to visualize and to verify the outcomes in the invivo intrastromal laser nanosurgery. More interesting, the activated keratocytes have been also observed in-vivo 24 hours after the laser nanosurgery with this system. Overall, these data suggest that multiphoton microscopy is a highly sensitive and promising technique for studying the morphometric properties of the microstructure of the corneal tissue and for assessing the intrastromal nanosurgery. With the help of the multiphoton-mediated imaging, the next generation of laser refractive surgery approaches based on the nonamplified femtosecond lasers with higher precision and less complications are being evaluated systematically.

  11. [Intrastromal refractive corneal surgery with pico-second Nd:YAG laser pulses].

    Science.gov (United States)

    Vogel, A; Asiyo-Vogel, M; Birngruber, R

    1994-10-01

    Intrastromal laser surgery with picosecond pulses aims to achieve refractive changes of the cornea without damaging the epithelium, Bowman's membrane, or the endothelium. For that, a tissue layer with well-defined thickness has to be evaporated by creating laser plasmas within the corneal stroma. We investigated the plasma formation and the plasma-induced shock wave emission and bubble generation (cavitation) in the cornea, as well as the tissue effects and the range for endothelial damage. The laser light source used was an Nd:YAG laser emitting pulses with a duration of 30 ps at a repetition rate of 10 Hz. Intrastromal plasma formation and cavitation were investigated in sheep eyes in vitro by means of time-resolved macro-photography with 20 ns exposure time. Photographs were taken at various delay times (3 microseconds-2 min) after the release of the Nd:YAG laser pulse. The morphology of the laser effects and the incidence of endothelial damage was investigated by light-microscopic inspection of histological cross sections of the irradiated corneas. The minimal plasma size at energies close to the breakdown threshold was about 40 microns. Using a laser effects could be created without causing microscopically detectable damage to the epithelium, endothelium, or Bowman's membrane. To avoid damage, the distance between endothelium and laser focus had to be larger than 150 microns. Shock wave-induced tissue damage was not observed, although the maximum shock wave pressure was up to 13 kbar. The laser-generated intrastromal cavities are at least 10 times larger than the plasma volume.(ABSTRACT TRUNCATED AT 250 WORDS)

  12. A new nanosecond UV laser at 355 nm: early results of corneal flap cutting in a rabbit model.

    Science.gov (United States)

    Trost, Andrea; Schrödl, Falk; Strohmaier, Clemens; Bogner, Barbara; Runge, Christian; Kaser-Eichberger, Alexandra; Krefft, Karolina; Vogel, Alfred; Linz, Norbert; Freidank, Sebastian; Hilpert, Andrea; Zimmermann, Inge; Grabner, Günther; Reitsamer, Herbert A

    2013-12-03

    A new 355 nm UV laser was used for corneal flap cutting in an animal model and tested for clinical and morphologic alterations. Corneal flaps were created (Chinchilla Bastards; n = 25) with an UV nanosecond laser at 355 nm (150 kHz, pulse duration 850 ps, spot-size 1 μm, spot spacing 6 × 6 μm, side cut Δz 1 μm; cutting depth 130 μm) and pulse energies of 2.2 or 2.5 μJ, respectively. Following slit-lamp examination, animals were killed at 6, 12, and 24 hours after treatment. Corneas were prepared for histology (hematoxylin and eosin [HE], TUNEL-assay) and evaluated statistically, followed by ultrastructural investigations. Laser treatment was tolerated well, flap lift was easier at 2.5 μJ compared with 2.2 μJ. Standard HE at 24 hours revealed intact epithelium in the horizontal cut, with similar increase in corneal thickness at both energies. Irrespective of energy levels, TUNEL assay revealed comparable numbers of apoptotic cells in the horizontal and vertical cut at 6, 12, and 24 hours, becoming detectable in the horizontal cut as an acellular stromal band at 24 hours. Ultrastructural analysis revealed regular morphology in the epi- and endothelium, while in the stroma, disorganized collagen lamellae were detectable representing the horizontal cut, again irrespective of energy levels applied. This new UV laser revealed no epi- nor endothelial damage at energies feasible for corneal flap cutting. Observed corneal swelling was lower compared with existing UV laser studies, albeit total energy applied here was much higher. Observed loss of stromal keratinocytes is comparable with available laser systems. Therefore, this new laser is suitable for refractive surgery, awaiting its test in a chronic environment.

  13. Clinical study of the clusters of diffuse lamellar keratitis after laser corneal refractive surgery

    Directory of Open Access Journals (Sweden)

    Qing-Hong Lin

    2017-06-01

    Full Text Available AIM: To investigate the potential causes and management of the clusters of diffuse lamellar keratitis(DLKafter laser corneal refractive surgery. METHODS: The study enrolled 98 eyes(53 patientscomplicated with DLK after receiving laser in situ keratomileusis(LASIK, FS-LASIK or small-incision lenticule extraction(SMILEin our center from February 10th,2016 to February 22th,2016. They were given clinical classification treatments according to corneal layer inflammatory extent and then followed up after 1, 3, 5, 7, 10d and 1mo. RESULTS: The clusters of DLK occurred 5 times in the study period. The incidence and degree of DLK significantly decreased after changed the sterilization, surgical equipments, temperature and humidity of the operating room. There were 80 eyes(82%had stage 1 DLK, 11 eyes(11%had stage 2, 4 eyes(4%had stage 3 and 3 eyes(3%had stage 4. The incidence of DLK after FS-LASIK was 40%(79 eyes in 42 patients, that after LASIK assistant by Hastome keratome was 45%(10 eyes in 5 patients, that after SMILE was 20%(9 eyes in 6 patients. After intensive treatment, as glucocorticoid treatment and flap lifting flushing, all cases recovered within 1mo. CONCLUSION: The outbreak of DLK may be associated with the disposable item, flushing liquor, temperature and humidity of the operating room. Early diagnosis, prevention and treatment are the key of decreasing the incidence of DLK.

  14. Femtosecond laser-assisted intrastromal corneal ring segment implantation for high astigmatism correction after penetrating keratoplasty.

    Science.gov (United States)

    Lisa, Carlos; García-Fernández, Miriam; Madrid-Costa, David; Torquetti, Leonardo; Merayo-Lloves, Jesús; Alfonso, José Fernando

    2013-11-01

    To assess the visual and refractive outcomes of femtosecond laser-assisted implantation of Ferrara-type intrastromal corneal ring segments (ICRS) in post-penetrating keratoplasty (PKP) eyes. Instituto Oftalmológico Fernández-Vega, Oviedo, Spain. Cohort study. Patients with previous PKP had ICRS implantation after femtosecond laser tunnel creation. The uncorrected (UDVA) and corrected (CDVA) distance visual acuities and residual refractive errors were recorded before and 6 months after ICRS implantation. The power vector method was used to analyze refractive errors preoperatively and postoperatively. This study enrolled 32 eyes of 30 patients. The mean UDVA (Snellen decimal) changed from 0.16 ± 0.15 (SD) preoperatively to 0.43 ± 0.28 postoperatively (Pastigmatism components were significantly reduced after ICRS implantation (Pastigmatism correction in post-PKP eyes. Copyright © 2013 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  15. 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.

  16. 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.

  17. Measure the spatial distribution of corneal elasticity by combining femtosecond laser induced breakdown spectroscopy and acoustic radiation force elasticity microscope

    Science.gov (United States)

    Sun, Hui; Li, Xin; Hu, Mingyong

    2017-08-01

    The unique spatial distribution of corneal elasticity is shown by the nonhomogeneous structure of the cornea. It is critical to understanding how biomechanics control corneal stability and refraction and one way to do this job is non-invasive measurement of this distribution. Femtosecond laser pulses have the ability to induce optical breakdown and produced cavitation in the anterior and posterior cornea. A confocal ultrasonic transducer applied 6.5 ms acoustic radiation forcechirp bursts to the bubble at 1.5 MHz while monitoring bubble position using pulse-echoes at 20 MHz. The laser induced breakdown spectroscopy (LIBS) were measured in the anterior and posterior cornea with the plasmas that induced by the same femtosecond laser to see whether the laser induced plasmas signals will show relationship to Young's modulus.

  18. Correlation between apical protrusion in the Scheimflug imaging and Corneal Hysteresis and Corneal Resistance factor by Ocular Response Analyzer, among refractive non-keratoconic Egyptian patients.

    Science.gov (United States)

    Refai, Tamer Adel

    2015-10-01

    Apical protrusion in the central 4-mm ring in the Scheimflug imaging (Pentacam), both for the anterior and posterior floats as well as Corneal Hysteresis and Corneal Resistance Factor by Ocular Response Analyzer (ORA), generally are considered important predictors for post-Lasik ectasia. The aim of this work was to find out if there is a statistically significant correlation between these different predictors and their correlation with the central corneal thickness for refractive non-keratoconic Egyptian patients trying to achieve a better decision and avoiding ectasia. This case-control study involved 142 eyes (of 77 patients with various refractive errors) arriving at the refractive surgery unit in the Research Institute of Ophthalmology in Giza (Egypt) in 2014-2015 seeking excimer laser ablation. The flattest, steepest keratometry readings, central corneal thickness as well as the apical protrusion in the central 4-mm ring, both for the anterior and posterior floats, in microns were measured by Scheimflug imaging. The Corneal Hysteresis and Corneal Resistance Factor were measured by the ocular response analyzer. Statistical analysis was performed by SPSS, using the Pearson correlation test. The spherical refractive error ranged from +7.00 to -13.00 diopters (-3.80 ± 2.89). The central pachymetry ranged from 494 to 634 μm (550.35 ± 32.13). For the central 4-mm ring, the apical protrusion ranged from 0 to +15 μ (6.93 ± 2.99) for the anterior float and from -3 to +20 μ (9.33 ± 4.55) for the posterior float. The Corneal Hysterisis (CH) ranged from 7 to 14.8 mmHg (10.18±1.44), while the Corneal Resistance Factor (CRF) ranged from 7.5 to 14.9 mmHg (10.58 ± 1.67). There was a strong positive correlation between the central corneal thickness and both Corneal Hysteresis (CH: r = 0.56, P ≤ 0.01) and Corneal Resistance Factor (r = 0.46, P ≤ 0.01). A significant correlation (P corneal thickness. Also, significant negative correlation (P Corneal Resistance

  19. 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.

  20. 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.

  1. Ten-year results of phototherapeutic keratectomy on recurrent corneal erosions

    Directory of Open Access Journals (Sweden)

    Belquiz Rodrigues do Amaral Nassaralla

    2012-02-01

    Full Text Available PURPOSE: To determine the ten-year visual results and outcomes of excimer laser phototherapeutic keratectomy (PTK for recurrent corneal erosions. METHODS: Twenty-six eyes of 23 patients with recurrent corneal erosions were treated by PTK from 1996 to 2000 at the Goiania Eye Institute, Brazil. All eyes had failed to respond to conventional therapy. Data regarding preoperative and postoperative best-spectacle-corrected visual acuity (BSCVA, spherical equivalent (SE, symptomatic relief, incidence of recurrence, and complications arising from the laser treatment were analyzed. The mean duration of symptoms prior to PTK was 18 months (range, 8 to 36 months. The corneal epithelium was debrided, and laser ablation was performed to a depth of 5 micron with an ablation zone of 7 to 9 mm, using the Technolas 217C Plano Scan excimer laser. Mean postoperative follow-up was 12 years (range, 10 to 14 years. RESULTS: At the last follow-up visit, 15 eyes (57.69% were symptomsfree. Five eyes (19.2% had occasional mild symptoms of irritation and photophobia upon awakening. Recurrence of painful corneal erosions occurred in six eyes (23.07%, which required a PTK retreatment. Twenty-four eyes had a preserved or improved BCVA, while 2 eyes showed deterioration of 1 line on Snellen test. Eleven eyes (42.3% had no change in SE, and the others (57.69% had a change of less than +/-0.75 diopters (D. There were no major complications during the follow-up period. CONCLUSION: Ten-year data show that PTK is a safe, fast, effective and minimal invasive choice of treatment for recurrent corneal erosions in patients who do not respond to conventional treatments.

  2. Application of Corvis ST to evaluate the effect of femtosecond laser-assisted cataract surgery on corneal biomechanics

    Science.gov (United States)

    Wei, Yinjuan; Xu, Lingxiao; Song, Hui

    2017-01-01

    The aim of the present study was to evaluate the effects of femtosecond laser-assisted cataract surgery (FLACS) and phacoemulsification on corneal biomechanics using corneal visualization Scheimpflug technology. The medical records of 50 eyes from 50 patients who received phacoemulsification and intraocular lens implantation because of age-related factors between June 2014 and September 2014 were retrospectively analyzed. FLACS was used in 12 eyes (FLACS group), and conventional phacoemulsification in 38 eyes (PHACO group). The evaluation of corneal biomechanical parameters included the first/second applanation time (A-time1/A-time2), the first/second applanation length (A-length1/A-length2), corneal velocity during the first/second applanation moment (Vin/Vout), highest concavity time, highest concavity-radius (HC-radius), peak distance (PD), deformation amplitude (DA), central corneal thickness (CCT), and intraocular pressure (IOP). The differences in A-length1/A-length2, IOP, CCT, PD, and DA were significant in the PHACO group between those before, 1 week after, and 1 month after surgery. No significant differences in corneal biomechanical parameters were found between those at 1 month after surgery and before surgery. There were significant differences in IOP and CCT in the FLACS group between those before, 1 week after, and 1 month after surgery. There were no significant differences in the other corneal biomechanical parameters. No significant differences were found in corneal biomechanical parameters between those 1 month after surgery and before surgery. There were significant differences in A-length1/A-length2, CCT, PD, and DA between the two groups at 1 week after surgery. There were no significant differences in corneal biomechanical parameters between the two groups at 1 month after surgery. In conclusion, the effect of FLACS on corneal biomechanics is smaller than that of phacoemulsification. The corneal biomechanical parameters are restored to

  3. Application of Corvis ST to evaluate the effect of femtosecond laser-assisted cataract surgery on corneal biomechanics.

    Science.gov (United States)

    Wei, Yinjuan; Xu, Lingxiao; Song, Hui

    2017-08-01

    The aim of the present study was to evaluate the effects of femtosecond laser-assisted cataract surgery (FLACS) and phacoemulsification on corneal biomechanics using corneal visualization Scheimpflug technology. The medical records of 50 eyes from 50 patients who received phacoemulsification and intraocular lens implantation because of age-related factors between June 2014 and September 2014 were retrospectively analyzed. FLACS was used in 12 eyes (FLACS group), and conventional phacoemulsification in 38 eyes (PHACO group). The evaluation of corneal biomechanical parameters included the first/second applanation time (A-time1/A-time2), the first/second applanation length (A-length1/A-length2), corneal velocity during the first/second applanation moment (Vin/Vout), highest concavity time, highest concavity-radius (HC-radius), peak distance (PD), deformation amplitude (DA), central corneal thickness (CCT), and intraocular pressure (IOP). The differences in A-length1/A-length2, IOP, CCT, PD, and DA were significant in the PHACO group between those before, 1 week after, and 1 month after surgery. No significant differences in corneal biomechanical parameters were found between those at 1 month after surgery and before surgery. There were significant differences in IOP and CCT in the FLACS group between those before, 1 week after, and 1 month after surgery. There were no significant differences in the other corneal biomechanical parameters. No significant differences were found in corneal biomechanical parameters between those 1 month after surgery and before surgery. There were significant differences in A-length1/A-length2, CCT, PD, and DA between the two groups at 1 week after surgery. There were no significant differences in corneal biomechanical parameters between the two groups at 1 month after surgery. In conclusion, the effect of FLACS on corneal biomechanics is smaller than that of phacoemulsification. The corneal biomechanical parameters are restored to

  4. In vivo confocal microscopic evaluation of corneal wound healing after femtosecond laser-assisted keratoplasty.

    Science.gov (United States)

    Shtein, Roni M; Kelley, Kurt H; Musch, David C; Sugar, Alan; Mian, Shahzad I

    2012-01-01

    To evaluate corneal wound healing after femtosecond laser-assisted keratoplasty (FLAK) using in vivo confocal microscopy (IVCM). Prospective, interventional, consecutive case series of 17 eyes after mushroom-shaped FLAK. IVCM was performed preoperatively and at 1, 3, 6, and 12 months postoperatively to assess wound healing. Mean keratocyte activation grade increased from preoperative levels to 1 month postoperatively in both the central (0.41 ± 0.62 to 1.73 ± 1.03) and peripheral (0.47 ± 0.52 to 1.57 ± 1.09) cornea, then gradually decreased through 12 months. Dendritic cells increased from preoperatively to 1 month postoperatively in both the central (0.71 ± 0.83 to 1.33 ± 0.98) and peripheral (0.79 ± 0.70 to 1.42 ± 0.90) cornea, then gradually decreased until 6 months postoperatively. Stromal reinnervation was 1 month postoperatively in 8 patients (50%). By 12 months, sub-epithelial nerves were observed centrally in 5 patients (45.5%). IVCM after FLAK shows an initial increase in keratocyte activation and dendritic cells that decrease over time. Corneal reinnervation is seen as early as 1 month postoperatively. Copyright 2012, SLACK Incorporated.

  5. Efficacy and safety of femtosecond laser-assisted corneal endothelial keratoplasty: a randomized multicenter clinical trial.

    Science.gov (United States)

    Cheng, Yanny Y Y; Schouten, Jan S A G; Tahzib, Nayyirih G; Wijdh, Robert-Jan; Pels, Elisabeth; van Cleynenbreugel, Hugo; Eggink, Catharina A; Rijneveld, Wilhelmina J; Nuijts, Rudy M M A

    2009-12-15

    To evaluate the efficacy and safety of femtosecond laser-assisted endothelial keratoplasty (FLEK) versus penetrating keratoplasty (PK) in patients with corneal endothelial disease. A randomized multicenter clinical trial of 80 eyes of 80 patients with corneal endothelial disease were randomized to FLEK or PK. Clinical outcomes (astigmatism and visual acuity) and incidence of postoperative complications were compared between the two groups. At 12 months, the percentage of eyes with a refractive astigmatism less than or equal to 3 diopters was higher in the FLEK group in comparison with the PK group (86.2% vs. 51.3%, P=0.004). The mean postoperative best corrected visual acuity was 20/70+/-2 lines in the FLEK group and 20/44+/-2 lines in the PK group (Pastigmatism and results in an absence of wound healing related problems in patients with endothelial disease. However, visual acuity is lower as compared with conventional PK, and the high level of endothelial cell loss warrants a modification of the insertion technique of the endothelial graft.

  6. 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.

  7. In vivo and in vitro evaluation of corneal damage induced by 1573 nm laser radiation

    Energy Technology Data Exchange (ETDEWEB)

    Courant, D.; Chapel, C. [CEA Fontenay-aux-Roses (DSV/DRR/SRBF), 92 (France). Dept. de Radiobiologie et de Radiopathologie; Pothier, C. [DGA-DCE/CTA/LOT, 94 - Arcueil (France); Sales, N. [CEA Fontenay-aux-Roses (DSV/DRM/SNV), 92 (France)

    2006-07-01

    Recent developments in laser technology have originated a variety of infrared laser sources between 1500-1700 nm called as 'eye-safe' which are gaining widespread use in industry, medicine and military applications. This spectral region has been called 'eye safe' because the cornea and aqueous humor absorb sufficient radiation to prevent nearly all potentially damaging radiation from reaching the retina whereas the lens does not absorb this spectral range and remains undamaged. However, in providing protection for the deeper layers of the eye, the cornea itself is susceptible to thermal damage. Previous studies, performed at 1540 nm with exposures less than 1 s, are inconsistent in the quantity of energy required to cause corneal damage. The purpose of this study was first, to determine the threshold damage exposure (E.D.{sub 50}) on rabbit cornea induced by a 3 ns single pulse emitted at 1573 nm, using clinical observations and histology and to compare the results to the limit values recommended by I.C.N.I.R.P. guidelines or international standards. Secondly, it was suggested to investigate the cellular effects of infrared radiation with biochemical techniques on cell cultures in order to specify a cellular damage threshold and a better understanding of the laser - tissue interaction and the corneal injury. The minimal damage criterion was defined by a shallow, very small depression of the epithelial surface with a mild fluorescein staining. The E.D.{sub 50} obtained with corneal beam diameter of 400 mm is 26.6 J.cm{sup -2}. The corresponding radiant exposure, calculated with the 1 mm aperture diameter recommended by I.C.N.I.R.P. guidelines or standards, is 4.3 J.cm{sup -2}. In vitro experiments have been carried out on primary keratocytes and H.T. 1080 epithelial cell line, using an expanded beam of 3.5 mm diameter on plates or Lab Tek holders. Cells were irradiated with 10 Hz pulse ratio frequency during 1, 2 or 3 s. The S A

  8. 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.

  9. 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.

  10. Corneal Laceration

    Medline Plus

    Full Text Available ... What Is Corneal Laceration? Corneal Laceration Symptoms What Causes Corneal Laceration? Corneal Laceration Diagnosis Corneal Laceration Treatment ... the corneal laceration is deep enough it can cause a full thickness laceration. This is when the ...

  11. Corneal Laceration

    Medline Plus

    Full Text Available ... What Is Corneal Laceration? Corneal Laceration Symptoms What Causes Corneal Laceration? Corneal Laceration Diagnosis Corneal Laceration Treatment What Is Corneal Laceration? Leer en Español: ¿Qué ...

  12. Diagnostic capability of scanning laser polarimetry with and without enhanced corneal compensation and optical coherence tomography.

    Science.gov (United States)

    Benítez-del-Castillo, Javier; Martinez, Antonio; Regi, Teresa

    2011-01-01

    To compare the abilities of the current commercially available versions of scanning laser polarimetry (SLP) and optical coherence tomography (OCT), SLP-variable corneal compensation (VCC), SLP-enhanced corneal compensation (ECC), and high-definition (HD) OCT, in discriminating between healthy eyes and those with early-to-moderate glaucomatous visual field loss. Healthy volunteers and patients with glaucoma who met the eligibility criteria were consecutively enrolled in this prospective, cross-sectional, observational study. Subjects underwent complete eye examination, automated perimetry, SLP-ECC, SLP-VCC, and HD-OCT. Scanning laser polarimetry parameters were recalculated in 90-degree segments (quadrants) in the calculation circle to be compared. Areas under the receiver operating characteristic curve (AUROCs) were calculated for every parameter in order to compare the ability of each imaging modality to differentiate between normal and glaucomatous eyes. Fifty-five normal volunteers (mean age 59.1 years) and 33 patients with glaucoma (mean age 63.8 years) were enrolled. Average visual field mean deviation was -6.69 dB (95% confidence interval -8.07 to -5.31) in the glaucoma group. The largest AUROCs were associated with nerve fiber indicator (0.880 and 0.888) for the SLP-VCC and SLP-ECC, respectively, and with the average thickness in the HD-OCT (0.897). The best performing indices for the SLP-VCC, SLP-ECC, and HD OCT gave similar AUROCs, showing moderate diagnostic accuracy in patients with early to moderate glaucoma. Further studies are needed to evaluate the ability of these technologies to discriminate between normal and glaucomatous eyes.

  13. 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

  14. 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

  15. 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.

  16. 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.

  17. Comparison of the change in posterior corneal elevation and corneal biomechanical parameters after small incision lenticule extraction and femtosecond laser-assisted LASIK for high myopia correction.

    Science.gov (United States)

    Wang, Bingjie; Zhang, Zhenyong; Naidu, Rajeev K; Chu, Renyuan; Dai, Jinhui; Qu, Xiaomei; Yu, Zhiqiang; Zhou, Hao

    2016-06-01

    To compare posterior corneal elevation (PCE) changes and corneal biomechanical changes post fematosecond laser-assisted laser in situ keratomileusis (FS-LASIK) and small incision lenticule extraction (SMILE) procedures using the Pentacam system and the Ocular Response Analyzer (ORA). Retrospective observational case series study. 106 patients with bilateral myopia who underwent either FS-LASIK (56 patients) or SMILE (50 patients) were reviewed, only the right eye was used in the analysis. Inclusion criteria include a spherical equivalent of -6.00DS and completion of 12 months follow up. The main outcome evaluated was change in PCE at 3 months, 6 months and 12 months post-operation using the Pentacam system. Corneal biomechanical parameters were evaluated at 6 and 12 months with the ORA. PCE change at 3 and 6 months were not significantly different between the two procedures (p=0.064, p=0.109 respectively). At 12 months, PCE change was greater in FS-LASIK than SMILE (p=0.048). One-way ANOVA showed that for either procedure, the change in PCE did not differ at 3, 6 or 12 months post operation. CH and CRF values were reduced after both procedures, with FS-LASIK demonstrating a greater reduction in CRF than SMILE at 6 and 12 months (p=0.037 and p=0.001). Both CH and CRF reduction correlated with PCE increase at 6 and 12 months. FS-LASIK demonstrated a greater increase in PCE than SMILE only at 12 months, as well as a greater reduction of CRF than SMILE. There were no significant differences in PCE change over time within either group. Copyright © 2016 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.

  18. 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.

  19. 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.

  20. Evaluation of a 345 nm Femtosecond Laser for Corneal Surgery with Respect to Intraocular Radiation Hazard.

    Directory of Open Access Journals (Sweden)

    Johannes Menzel-Severing

    Full Text Available We report our findings from a preclinical safety study designed to assess potential side effects of corneal ultraviolet femtosecond laser treatment on lens and retina.Refractive lenticules (-5 dpt with a diameter of 6 mm were created in the right cornea of eight Dutch Belted rabbits. Radiant exposure was 0.5 J/cm² in two animals and 18 J/cm² in six animals. The presence of lens opacities was assessed prior to and up to six months following laser application using Scheimpflug images (Pentacam, Oculus and backscatter analysis (Opacity Lensmeter 702, Interzeag. Ganzfeld flash and flicker electroretinogram (ERG recordings were obtained from both eyes prior to and up to six weeks following laser application. At the study endpoint, retinas were examined by light microscopy.Independent of energy dose applied, no cataract formation could be observed clinically or with either of the two objective methods used. No changes in ERG recordings over time and no difference between treated and untreated eye were detected. Histologically, retinal morphology was preserved and retinal pigment epithelium as well as photoreceptor inner and outer segments appeared undamaged. Quantitative digital image analysis did not reveal cell loss in inner or outer nuclear layers.Our analysis confirms theoretical considerations suggesting that ultraviolet femtosecond laser treatment of the cornea is safe for intraocular tissues. Transmitted light including stray light induces no photochemical effects in lens or retina at energy levels much higher than required for the clinical purpose. These conclusions cannot be applied to eyes with pre-existing retinal damage, as these may be more vulnerable to light.

  1. A histological study of rabbit corneas after transepithelial corneal crosslinking using partial epithelial photoablation or ethanol treatment

    Directory of Open Access Journals (Sweden)

    Mehmet Cuneyt Ozmen

    2014-12-01

    Full Text Available AIM: To evaluate the histological changes after transepithelial corneal crosslinking (CXL using partial thickness excimer laser ablation or epithelial ethanol application in an experimental rabbit study.METHODS: Right eyes of twenty-four rabbits were studied. Four eyes received total epithelial debridement (group I. Four eyes received partial thickness epithelial ablation with excimer laser (group II. Twelve eyes were treated with different durations (30s and 60s and concentrations (18% to 48% of ethanol (group III. Riboflavin was applied for 30min intervals along with topical proparacaine drops with benzalkonium chloride, and 370 nm irradiation was performed for 30min, while riboflavin was instilled every 3min. Four eyes (group IV received 48% ethanol for 30s without riboflavin and irradiation. Eyes were collected after 24h and examined histologically.RESULTS: All eyes in group I showed keratocyte loss in the superficial 300 µ of corneal storma. In group II, 1-4 layers of epithelium were preserved and no keratocyte loss occurred. In group III, CXL after treatment with ethanol up to 24% concentration and up to 60s revealed no keratocyte loss. CXL after treatment with 48% and higher ethanol concentrations yielded keratocyte loss in the superficial 200 µ to 300 µ of cornea.CONCLUSION: Incomplete excimer laser ablation of the epithelium or treatment with ethanol up to 24% concentration and up to 60s duration yielded no stromal keratocyte loss. To get the same histological appearance seen in epithelial debridement group, partial thickness excimer laser epithelial ablation or ethanol application is not adequate for transepithelial CXL.

  2. 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.

  3. 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.)

  4. 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.

  5. 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.

  6. 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...

  7. 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.

  8. 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.

  9. Intrastromal corneal ring segment implantation by femtosecond laser for the correction of residual astigmatism after penetrating keratoplasty.

    Science.gov (United States)

    Prazeres, Tatiana Moura Bastos; Souza, Allan Cezar da Luz; Pereira, Nicolas Cesário; Ursulino, Fábio; Grupenmacher, Leon; de Souza, Luciene Barbosa

    2011-12-01

    To evaluate the safety and efficacy of intracorneal ring segments (ICRSs) aided by femtosecond (FS) laser for the correction of residual astigmatism after penetrating keratoplasty (PKP). This retrospective noncomparative study comprised 14 eyes of 14 patients with high astigmatism after PKP who had ICRS implantation by femtosecond laser. The study evaluated uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), refractive astigmatism, and corneal maximum curvature. The CDVA postoperatively improved after 3 months (P 0.999) as well as the UDVA (P = 0.276). The preoperative astigmatism was higher than that after surgery (P = 0.001). The preoperative maximum curvature was higher than that of the postoperative maximum curvature (P astigmatism post-PKP was safe and showed satisfactory results. It reduced refractive astigmatism and maximum corneal curvature and improved UDVA and CDVA.

  10. Corneal crosslinking with riboflavin and ultraviolet A. Part II. Clinical indications and results.

    Science.gov (United States)

    Raiskup, Frederik; Spoerl, Eberhard

    2013-04-01

    Changes in the biomechanical properties of the human cornea play an important role in the pathogenesis of corneal ectatic diseases. A variety of conditions in primary acquired (keratoconus and pellucid marginal degeneration) or secondary induced (iatrogenic keratectasia after excimer refractive laser surgery) corneal ectatic disorders lead to reduced biomechanical resistance. Corneal collagen crosslinking (CXL) has emerged as a promising technique to slow or even to stop the progression of these corneal ectatic pathologies. In this procedure, riboflavin (vitamin B2) is administered in conjunction with ultraviolet A light (UVA, 365 nm). This interaction causes the formation of reactive oxygen species, leading to the formation of additional covalent bonds between collagen molecules, with consequent biomechanical stiffening of the cornea. Although this method is not yet accepted as an evidence-based medicine modality for the treatment of corneal primary or secondary ectasias, the results of prospective, randomized studies of CXL used in the treatment of these pathologic entities show significant changes in the properties of corneal tissue. This procedure is currently the only etiopathogenetic approach in ectatic eyes that can delay or stop the process of cornea destabilization, reducing the necessity for keratoplasty. Despite promising results, CXL is associated with issues that include long-term safety and duration of the stabilizing effect. Combination of CXL with vision-improving procedures, such as topography-guided custom ablation and implantation of intracorneal ring segments of phakic intraocular lenses, may expand the indications for this procedure. Copyright © 2013 Elsevier Inc. All rights reserved.

  11. Corneal topography six years after photorefractive keratectomy for myopia and myopic astigmatism.

    Science.gov (United States)

    Serrao, Sebastiano; Lombardo, Giuseppe; Lombardo, Marco; Palombi, Marino; Roberts, Cynthia J

    2009-05-01

    To analyze the 6-year response of corneal topography to photorefractive keratectomy (PRK) for myopia and myopic astigmatism. Twenty patients (40 eyes) who had PRK using the Technolas Keracor 217C excimer laser platform were followed up to 6 years after surgery. The eyes were subdivided into three groups according to the preoperative spherical equivalent refraction and astigmatism component. Corneal topographic maps were obtained with a Placido disk topographer (Keratron Scout). The pre- and postoperative topographical data were imported into custom software, which computed the average composite corneal map and average difference map for each study group to quantify the anterior corneal changes following laser ablation. The software defined three concentric zones of the surface topography, allowing characterization of the regional corneal response following surgery. At 6 years, no changes in the surface topographic configuration of the central cornea were assessed following spherical myopic ablations in comparison with 1 year postoperatively. A slight peripheral flattening of approximately 0.60 diopters (D) (P < .001) was measured following the higher myopic ablations at 6 years compared with 1 year postoperatively. Minimal changes, of approximately 0.30 D (P < .001), in the anterior central cornea were observed following astigmatic correction during follow-up. Photorefractive keratectomy for the correction of myopia provides stable comeal topography, with no clinically significant changes in the curvature profile at 6 years after surgery.

  12. Comparison of corneal hysteresis and corneal resistance factor after small incision lenticule extraction and femtosecond laser-assisted LASIK: a prospective fellow eye study.

    Science.gov (United States)

    Agca, Alper; Ozgurhan, Engin Bilge; Demirok, Ahmet; Bozkurt, Ercument; Celik, Ugur; Ozkaya, Abdullah; Cankaya, Ilker; Yilmaz, Omer Faruk

    2014-04-01

    To compare corneal hysteresis (CH) and corneal resistance factor (CRF) between eyes treated with small incision lenticule extraction (SMILE) and femtosecond laser-assisted laser in situ keratomileusis (femto-LASIK). Beyoğlu Eye Training and Research Hospital. Prospective comparative case series. Sixty eyes from 30 patients with bilateral myopia or myopic astigmatism were studied. Inclusion criteria were spherical equivalent of subjective manifest refraction (SE) <10diopters (D) and a difference ≤0.50D between the SEs of both eyes. One eye of each patient was treated with SMILE, and the fellow eye underwent femto-LASIK. Randomization was performed using a sealed envelope system. The main outcome measures were CH and CRF measured preoperatively and postoperatively (1 and 6 months). Preoperative SE was similar in both groups (p=0.852). CH and CRF values were reduced postoperatively in both groups compared to their corresponding preoperative values (p<0.001). At the 6-month follow-up visit, the mean CH values in the SMILE and femto-LASIK groups were 8.95±1.47 and 9.02±1.27, respectively (p=0.852), and the mean CRF values were 7.77±1.37 and 8.07±1.26, respectively (p=0.380). CH and CRF decreased after SMILE. There were no differences between SMILE and femto-LASIK treatments in postoperative CH or CRF values. Crown Copyright © 2013. Published by Elsevier Ltd. All rights reserved.

  13. RECURRENT CORNEAL EROSION SYNDROME (a review

    Directory of Open Access Journals (Sweden)

    S. V. Trufanov

    2015-01-01

    is ineffective, surgical procedures (Bowman’s membrane polishing with diamond drill, anterior stromal puncture, excimer laser phototherapeutic keratectomy are required. RCE therapy decision making should consider disease severity, the presence of concurrent pathology, medical experience and surgical instrument availability if needed. 

  14. [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.

  15. Research of cornea section's shape ablated by 193-nm ArF laser spots

    Science.gov (United States)

    Zhu, Zhiqiang; Yu, Yinshan; Deng, Guoqing

    2005-11-01

    The ablation theory of cornea and biology effect by 193-nm ArF excimer laser are introduced. The ablation tracks model is put forward to make laser spots scan around cornea by many steps and many areas to change cornea curvature. The corneal average ablation curve is calculated by software so as to explain the feasibility of the ablation tracks model. By analyzing the actual ablation shapes of many arbitrary cornea sections, the optimal ablation method for deciding the random position of every laser spot in every ablation track is obtained. Experiments combining the ablation model with the device testify the energy stability of laser spots and the accuracy of rectifying anisometropia.

  16. 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.

  17. 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%.

  18. 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.

  19. Clinical outcomes of corneal wavefront customized ablation strategies with SCHWIND CAM in LASIK treatments.

    Science.gov (United States)

    Arbelaez, Maria Clara; Vidal, Camila; Arba-Mosquera, Samuel

    2009-09-01

    To evaluate the clinical outcomes of aspheric corneal wavefront (CW) ablation profiles in LASIK treatments. Thirty eyes treated with CW ablation profiles were included after a follow-up of 6 months. In all cases, standard examinations including preoperative and postoperative wavefront analysis with a CW topographer (Optikon Keratron Scout) were performed. Custom Ablation Manager (CAM) software was used to plan corneal wavefront customized aspheric treatments, and the ESIRIS flying spot excimer laser system was used to perform the ablations (both SCHWIND eye-tech-solutions, Kleinhostheim, Germany). Clinical outcomes were evaluated in terms of predictability, refractive outcome, safety, and wavefront aberration. In general, the postoperative uncorrected visual acuity and the best corrected visual acuity improved (p < 0.001). In particular, the trefoil, coma, and spherical aberrations, as well as the total root-mean-square values of higher order aberrations, were significantly reduced (p < 0.05) when the pre-existing aberrations were greater than the repeatability and the biological noise. The study results indicate that the aspheric corneal wavefront customized CAM approach for planning ablation volumes yields visual, optical, and refractive results comparable to those of other wavefront-guided customized techniques for correction of myopia and myopic astigmatism. The CW customized approach shows its strength in cases where abnormal optical systems are expected. Apart from the risk of additional ablation of corneal tissue, systematic wavefront-customized corneal ablation can be considered as a safe and beneficial method.

  20. Corneal Laceration

    Medline Plus

    Full Text Available ... Corneal Laceration? Corneal Laceration Diagnosis Corneal Laceration Treatment What Is Corneal Laceration? Leer en Español: ¿Qué Es una Laceración de la Córnea? Written By: Daniel ...

  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. Pseudophakic astigmatism reduction with femtosecond laser-assisted corneal arcuate incisions: a pilot study

    Directory of Open Access Journals (Sweden)

    Blehm C

    2017-01-01

    Full Text Available Clayton Blehm,1 Richard Potvin2 1Gainesville Eye Associates, Gainesville, GA, 2Science in Vision, Akron, NY, USA Purpose: The aim of this study was to assess the effectiveness of the Verion-LenSx guided arcuate incision technique to reduce refractive astigmatism in a pseudophakic population. Patients and methods: A prospective single-arm study was conducted in which one or both eyes of subjects required reduction of 1.0–2.0 D of refractive astigmatism after previous cataract surgery or refractive lens exchange. The surgeon used the refractive cylinder in the eye and the Woodcock astigmatism nomogram for preoperative planning, while the LenSx femtosecond laser with the Verion Image Guided System was used to create all arcuate incisions. The primary outcome measure was the uncorrected monocular distance visual acuity (UCVA. Secondary outcome measures included the change in corneal astigmatism, the change in refractive astigmatism, the best-corrected visual acuity and spectacle independence at distance from preoperative stage to 1 month and 2 months postoperatively. Results: Twenty-eight eyes of 18 subjects were treated. The best-corrected visual acuity at the 2-month postoperative (PO stage was not statistically significantly different from the preoperative visual acuity (0.02 logarithm of the minimum angle of resolution [logMAR] in both cases, P>0.05. Uncorrected visual acuity was statistically significantly better at the 2-month PO stage relative to the preoperative value (0.14 versus 0.34 logMAR, P<0.01. The mean change in refractive cylinder from the preoperative stage to the 2-month PO stage was 1.0 D. At the 2-month PO stage, two-thirds of the subjects (12/18 reported that they did not use glasses for distance vision and that their spectacle use for distance vision at 2 months was “lower” or “much lower” than the preoperative stage; in 71% of eyes (20/28, the residual refractive cylinder was ≤0.50 D. Vector changes in

  3. Algorithm for correcting the keratometric error in the estimation of the corneal power in eyes with previous myopic laser refractive surgery.

    Science.gov (United States)

    Camps, Vicente J; Piñero, David P; Mateo, Veronica; Ribera, David; de Fez, Dolores; Blanes-Mompó, Francisco J; Alzamora-Rodríguez, Antonio

    2013-11-01

    To calculate theoretically the errors in the estimation of corneal power when using the keratometric index (nk) in eyes that underwent laser refractive surgery for the correction of myopia and to define and validate clinically an algorithm for minimizing such errors. Differences between corneal power estimation by using the classical nk and by using the Gaussian equation in eyes that underwent laser myopic refractive surgery were simulated and evaluated theoretically. Additionally, an adjusted keratometric index (nkadj) model dependent on r1c was developed for minimizing these differences. The model was validated clinically by retrospectively using the data from 32 myopic eyes [range, -1.00 to -6.00 diopters (D)] that had undergone laser in situ keratomileusis using a solid-state laser platform. The agreement between Gaussian (Pc) and adjusted keratometric (Pkadj) corneal powers in such eyes was evaluated. It was found that overestimations of corneal power up to 3.5 D were possible for nk = 1.3375 according to our simulations. The nk value to avoid the keratometric error ranged between 1.2984 and 1.3297. The following nkadj models were obtained: nkadj = -0.0064286r1c + 1.37688 (Gullstrand eye model) and nkadj = -0.0063804r1c + 1.37806 (Le Grand). The mean difference between Pkadj and Pc was 0.00 D, with limits of agreement of -0.45 and +0.46 D. This difference correlated significantly with the posterior corneal radius (r = -0.94, P < 0.01). The use of a single nk for estimating the corneal power in eyes that underwent a laser myopic refractive surgery can lead to significant errors. These errors can be minimized by using a variable nk dependent on r1c.

  4. 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.

  5. Corneal imaging of intrastromal femtosecond laser treatment for presbyopia (Intracor(®)).

    Science.gov (United States)

    Trinh, L; Francoz, M; Chong-Sit, D; Labbé, A; Dupont-Monod, S; Baudouin, C

    2013-10-01

    To evaluate anatomic appearance and corneal cellular modifications after monocular Intracor(®) procedure with two different anterior segment imaging techniques within the first postoperative year. Four patients underwent an Intracor(®) procedure in one eye performed at Clinique de la vision, and corneal imaging was performed in Quinze-Vingts National Ophthalmology Hospital. Slit-lamp photography, confocal microscopy with Heidelberg retinal tomography (HRT) and anterior segment spectral-domain optical coherence tomography (OCT) were performed 2 days, and 1, 6, and 12 months after the procedure. Confocal microscopy showed strong cellular activation of keratocytes within the first postoperative month which diminished over time. The linear femtosecond incisions appeared as hyper-reflective regular lines and reflectivity decreased throughout the follow-up period. After 6 months, a fibrotic process with appearance of corneal scars was visible as small intrastromal hyper-reflective lines and thick hyper-reflective spicules around the incisions and remained stable over time. On spectral-domain OCT, the size and depth of the incisions decreased from the center to the periphery. Visibility of the corneal femtosecond incisions on OCT decreased from day 2 until they almost disappeared at 12 months. The incision angles seemed to curve progressively from the center to the periphery in their deep portion on the peripheral rings. Corneal cellular modifications found on HRT, anatomical features, and the sizes of the intrastromal rings, may provide valuable information on this new refractive technique. Copyright © 2013 Elsevier Masson SAS. All rights reserved.

  6. [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).

  7. Corneal Ulcer

    Science.gov (United States)

    ... Español Eye Health / Eye Health A-Z Corneal Ulcer Sections What Is a Corneal Ulcer? Corneal Ulcer ... Diagnosis Corneal Ulcer Treatment What Is a Corneal Ulcer? Leer en Español: ¿Qué es una Úlcera de ...

  8. Biomechanical corneal changes induced by different flap thickness created by femtosecond laser

    Directory of Open Access Journals (Sweden)

    Fabricio W. Medeiros

    2011-01-01

    Full Text Available OBJECTIVE: To evaluate the impact of the creation of corneal flaps at different thicknesses on the biomechanical properties of swine corneas. METHOD: Twelve swine eyes were obtained to form two groups: 100 μm flap thickness and 300 μm flap thickness. Each eye was submitted to the following examinations: raster topography to investigate corneal curvature alterations, ocular response analyzer to investigate corneal hysteresis change, optical coherence tomography to measure central corneal and flap thickness and sonic wave propagation velocity as a measure of stiffness, before and immediately after flap creation. After flap amputation, surface wave velocity measurements were repeated. RESULTS: Measured flap thicknesses were statistically different for thin and thick flap groups, with an average of 108.5 + 6.9 and 307.8 + 11.5 μm respectively. Hysteresis and corneal resistance factor did not change significantly after flap creation in the thin flap group. With thicker flaps, both parameters decreased significantly from 8.0 +1.0 to 5.1 +1.5 mmHg and from 8.2 + 1.6 to 4.1 +2.5 mmHg respectively. Simulated keratometry values increased in the thick flap group (from 39.5 + 1 D to 45.9+1.2 D after flap creation but not in the thin flap group (from 40.6 + 0.6 D to 41.4+ 1.0 D. Regarding surface wave velocity analysis, the surgical procedures induced statistically lower results in some positions. CONCLUSION: In the experimental conditions established by this model, thicker flaps presented a greater biomechanical impact on the cornea.

  9. 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.

  10. Combined femtosecond laser-assisted intracorneal ring segment implantation and corneal collagen cross-linking for correction of keratoconus

    Directory of Open Access Journals (Sweden)

    Ibrahim O

    2016-03-01

    Full Text Available Osama Ibrahim,1 Ahmed Elmassry,1 Amr Said,1,2 Moones Abdalla,2 Hazem El Hennawi,1 Ihab Osman1 1Department of Ophthalmology, Alexandria University, Alexandria, Egypt; 2Roayah Vision Correction Center, Alexandria, Egypt Purpose: To assess the safety, predictability, and effectiveness of Keraring intrastromal corneal ring segments (ICRS insertion assisted by femtosecond laser and corneal collagen cross-linking (CXL for keratoconus correction. Patients and methods: In this prospective, noncomparative, and interventional case series, 160 eyes of 100 adult keratoconus patients with poor best-corrected visual acuity (BCVA (less than 0.7 and intolerance to contact lens wear were included. Patients underwent femtosecond laser-assisted placement of ICRS and CXL. All patients were examined for a complete ophthalmological test: uncorrected visual acuity (UCVA, BCVA, spherical equivalent, keratometry (K1-flat and K2-steep, pachymetry, and Scheimpflug imaging with the Pentacam at 1 week and at 1, 3, and 6 months postoperatively. Results: At 6 months, a significant difference was observed (P<0.001 in mean UCVA and BCVA from 0.92±0.677 and 0.42±0.600 logMAR preoperatively to 0.20±0.568 and 0.119±0.619 logMAR, respectively. Mean spherical equivalent refractions were significantly lower (P<0.001 at 6 months. Mean keratometry (K also significantly reduced (P<0.001 from 50.93±5.53 D (K1-flat and 55.37±5.76 D (K2-steep to 47.32±4.61 and 51.08±5.38 D, respectively. In terms of pachymetry, no significant difference was observed preoperatively versus postoperatively (P=1.000. Conclusion: Keraring ICRS insertion assisted by femtosecond laser and corneal CXL provided significant improvement in visual acuity, spherical equivalent, and keratometry, which suggests that it may be effective, safe, and predictable for keratoconus correction. Keywords: keratometry, pachymetry, keratectesia, Pentacam, irregular astigmatism

  11. Modificaciones de la curvatura posterior corneal después de la cirugía refractiva láser Modifications in the corneal posterior curve after laser refractive surgery

    Directory of Open Access Journals (Sweden)

    Lorelei Ortega Díaz

    2011-06-01

    Full Text Available OBJETIVO: Describir las modificaciones de la curvatura posterior corneal en pacientes sometidos a cirugía refractiva láser en el Instituto Cubano de Oftalmología "Ramón Pando Ferrer" en el período de mayo a octubre de 2010. MÉTODOS: Se realizó un estudio descriptivo, longitudinal y prospectivo, con un universo de 257 pacientes (504 ojos sometidos a cirugía refractiva láser. La muestra quedó conformada por 31 pacientes (59 ojos. Se analizaron variables como edad, sexo, equivalente esférico, paquimetría preoperatoria, cantidad de ablación, estroma residual y diferencia de elevación posterior corneal, esta última obtenida del mapa de diferencia del topógrafo Galilei, con medición preoperatoria al mes y a los tres meses de la cirugía. Mediante análisis de regresión múltiple fueron valorados dichos cambios de la paquimetría, la cantidad de ablación y el estroma residual. RESULTADOS: El equivalente esférico, la paquimetría, la cantidad de ablación y el estroma residual se encontraron dentro de los parámetros de seguridad establecidos. La diferencia promedio de la elevación corneal posterior fue de 15,62 µm al mes y de 11,78 µm a los tres meses, con disminución significativa con el tiempo (p= 0,000. Se observó asociación con la paquimetría preoperatoria y el estroma residual, y se encontró una correlación inversa entre este último y la elevación corneal posterior a los tres meses. CONCLUSIONES: La cirugía refractiva láser induce un aumento precoz en la elevación corneal posterior, con disminución progresiva hacia el tercer mes. Los factores que más influyeron en estos cambios fueron el estroma residual y la paquimetría preoperatoria.OBJECTIVES: To describe the modifications in the corneal posterior curve in patients underwent laser refractive surgery in the "Ramón Pando Ferrer" Cuban Institute of Ophthalmology from May to October, 2020. METHODS: A prospective, longitudinal and descriptive study was conducted

  12. Association of fluorescein anterior corneal mosaic and corneal K-structures by in vivo laser confocal microscopy in patients with keratoconus.

    Science.gov (United States)

    Kobayashi, Akira; Yokogawa, Hideaki; Mori, Natsuko; Masaki, Toshinori; Sugiyama, Kazuhisa

    2017-01-01

    To report the in vivo laser confocal microscopy findings of corneas with keratoconus, with special attention to abnormality of Bowman's layer and sub-Bowman's fibrous structures (Kobayashi-structures [K-structures]). Sixteen keratoconic eyes in 8 consecutive patients with keratoconus (4 males, 4 females, mean age, 41.1 years) were included in this study. Slit-lamp biomicroscopic photos were taken with or without fluorescein staining. The existence of anterior corneal mosaic (ACM) after eyelid rubbing under fluorescein staining was documented. In vivo laser confocal microscopic examinations were performed for all patients in both the central cone and the peripheral cornea to examine the existence of K-structures. According to the Amsler-Krumeich scale, the eyes were graded as follows: stage 1 (n=3), stage 2 (n=1), stage 3 (n=1), and stage 4 (n=11). ACM was observed in 7 eyes (61.1%) in the cone area and 16 eyes (100%) in the peripheral cornea among all keratoconic eyes enrolled in this study. In addition, K-structures were observed in the 7 eyes (61.1%) and 16 eyes (100%) in the peripheral cornea among all keratoconic eyes. The presence of the K-structures was completely matched (100%) with the presence of ACM in both the central cone and the peripheral cornea. In 11 eyes with stage 4 keratoconus, ACM and K-structure was absent in 9 eyes (81.8%) in the cone area. On the contrary, in 5 eyes with mild-to-moderate keratoconus (grade 1 to 3), ACM and K-structure was present in all eyes (100%) in the cone area. The absent ratio of ACM and K-structures in the cone area was significantly higher in stage 4 severe keratoconus compared to mild-to-moderate keratoconus (grade 1 to 3) (Fisher, P=0.005). The existence of ACM and K-structures in both the central cone and the peripheral cornea showed perfect accord in patients with keratoconus, indicating a strong association of ACM and K-structures in patients with keratoconus. With the progress of the keratoconus, it seemed that

  13. Indications, results, and complications of refractive corneal surgery with mechanical methods.

    Science.gov (United States)

    Hoffmann, F; Schüler, A

    1995-08-01

    Radial keratotomy (RK) incisions permanently weaken the cornea. This structural weakening can cause several complications and side effects, including diurnal fluctuation, progressive hyperopic shift, and the potential for traumatic rupture of the keratotomy scars. Minimally invasive-RK may be a useful alternative to reduce the invasiveness of RK while retaining its efficacy. Mild myopia can be treated by either RK or photorefractive keratectomy. Patients treated by RK in the first eye and photorefractive keratectomy in the second eye preferred the speed of recovery and the clarity of vision with RK. Combining the microkeratome and the excimer laser appears to be an ideal technique to correct high myopia. Laser ablation of the corneal lenticule while securely fixed by the suction ring in the Berlin microkeratome offers the advantage of perfect centration and fixation. Hexagonal keratotomy, used to treat hyperopia, appears to be an unpredictable, unsafe surgical procedure.

  14. 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.

  15. Real-time mapping of the corneal sub-basal nerve plexus by in vivo laser scanning confocal microscopy

    Science.gov (United States)

    Guthoff, Rudolf F.; Zhivov, Andrey; Stachs, Oliver

    2010-02-01

    The aim of the study was to produce two-dimensional reconstruction maps of the living corneal sub-basal nerve plexus by in vivo laser scanning confocal microscopy in real time. CLSM source data (frame rate 30Hz, 384x384 pixel) were used to create large-scale maps of the scanned area by selecting the Automatic Real Time (ART) composite mode. The mapping algorithm is based on an affine transformation. Microscopy of the sub-basal nerve plexus was performed on normal and LASIK eyes as well as on rabbit eyes. Real-time mapping of the sub-basal nerve plexus was performed in large-scale up to a size of 3.2mm x 3.2mm. The developed method enables a real-time in vivo mapping of the sub-basal nerve plexus which is stringently necessary for statistically firmed conclusions about morphometric plexus alterations.

  16. Comparison of mechanical and femtosecond laser tunnel creation for intrastromal corneal ring segment implantation in keratoconus: prospective randomized clinical trial.

    Science.gov (United States)

    Kubaloglu, Anil; Sari, Esin Sogutlu; Cinar, Yasin; Cingu, Kürşat; Koytak, Arif; Coşkun, Erol; Ozertürk, Yusuf

    2010-09-01

    To compare the outcomes of mechanical and femtosecond laser-assisted tunnel creation for intrastromal corneal ring segment (ICRS) implantation in eyes with keratoconus. Kartal Training and Research Hospital, Istanbul, Turkey. In this prospective study, consecutive eyes with keratoconus were randomly assigned to have ICRS tunnel creation with a mechanical device or a femtosecond laser. Keraring ICRS with a 5.0 mm diameter and 160-degree arc length were implanted in all cases. The uncorrected (UDVA) and corrected (CDVA) distance visual acuities, refraction, and keratometry (K) readings were measured preoperatively and 1 year postoperatively, and the data in the mechanical group and the femtosecond group were compared statistically. One year postoperatively, there was significant improvement in UDVA, CDVA, K readings, spherical equivalent (SE), and manifest sphere and cylinder in both groups (Pmechanical group and 2.0 lines in the femtosecond group and the CDVA by 3.3 lines and 2.7 lines, respectively; the mean reduction in maximum keratometry was 4.50 diopters (D) and 4.70 D, respectively, and the mean reduction in SE, 3.18 D and 3.09 D, respectively. There were no statistically significant differences between the 2 groups in visual or refractive results (P>.05). Anterior corneal perforation, superficial segment placement, and segment extrusion occurred in 1 eye each in the mechanical group. Segment migration occurred in 1 eye in the femtosecond group. Despite intraoperative complications in the mechanical group, the visual and refractive outcomes were similar to those in the femtosecond group. Copyright (c) 2010 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  17. Influence of LASIK on scanning laser polarimetric measurement of the retinal nerve fibre layer with fixed angle and customised corneal polarisation compensation

    Science.gov (United States)

    Holló, G; Katsanos, A; Kóthy, P; Kerek, A; Süveges, I

    2003-01-01

    Background/aim: Retinal nerve fibre layer thickness (RNFLT), as measured with scanning laser polarimetry using the fixed angle corneal polarisation compensator (SLP-F), has been found to be reduced after uncomplicated laser assisted in situ keratomileusis (LASIK) compared to the pre-LASIK measurement. Since this virtual RNFLT thinning is attributed to the corneal changes induced by the LASIK, the authors investigated whether customised corneal polarisation compensation (SLP-C), which compensates for the actual corneal polarisation during each measurement, can avoid the LASIK induced, virtual changes of the polarimetric RNFLT values. Methods: Scanning laser polarimetry using both the SLP-F and SLP-C methods (GDx-Access, software version 5.0) was performed on 15 consecutive healthy subjects with no eye disease who underwent LASIK for ametropia correction. The SLP measurements were performed before the surgery, then on day 1 and day 6 after LASIK. Thickness data from images of one randomly selected eye per subject were analysed using the ANOVA and Scheffe multiple comparison tests. Results: Superior maximum, inferior maximum, normalised superior area, and normalised inferior area (SLP parameters representing the RNFLT at the superior and inferior poles of the optic nerve head) remained unchanged with SLP-C (ANOVA, p>0.05) but decreased (superior maximum, normalised superior area, Scheffe test, p0.05) after LASIK. Superior to nasal ratio, symmetry of the superior and inferior RNFLT as well as the parameter showing the probability of having glaucoma (called “the number”) remained unchanged with both types of corneal compensation (ANOVA, p>0.05). With SLP-C the parameter ellipse average thickness increased after LASIK (Scheffe test, p = 0.021). No parameter value altered between day 1 and day 6 after LASIK, for either method. Conclusion: The results suggest that the LASIK induced decrease of the polarimetric RNFLT, which is consistently detected with polarimeters

  18. 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.

  19. Current approaches to the intraocular correction of postoperative aphakia after corneal refractive surgery (a review

    Directory of Open Access Journals (Sweden)

    Yu. A. Gusev

    2015-01-01

    Full Text Available Cataract surgery after radial keratotomy (RK represents many challenges as many patients who had RK are now developing visually significant cataracts. Currently, cataract surgery is not only the exchange of opaque lens but a refractive procedure as well. Despite a huge armamentarium of diagnostic methods, intraocular lens (IOL power calculations in these patients can be inaccurate and are associated with residual refractive errors for many reasons (overestimation of the corneal power by keratometry and corneal topography, errors in the assessment of effective lens position, inadequate selection of power calculation formulas. Methods based on refractive history which consider refraction and K values before corneal refractive surgery and its refractive result before cataract development as well as methods based on corneal topography are the most accurate methods to neutralize keratometry errors. Methods of «true» refraction estimation using correction coefficients which were calculated based on regression analysis of IOL implantation results after corneal refractive surgery are of significant importance as well. Patients with prior RK who undergo cataract surgery often require intraocular correction of astigmatism. The techniques include positioning and modifications of tunnel incision, anterior dosed keratotomy, excimer laser surgery, and toric IOL implantation. Finally, phaco technique should be carefully selected in patients with prior RK. Intraoperative dehiscence of RK incisions is the key challenge. 1.8‑2.2‑mm corneal incision placed between keratotomy incisions prevents this complication. In numerous keratotomy incisions, scleral tunnel is recommended.

  20. BMP7 gene transfer via gold nanoparticles into stroma inhibits corneal fibrosis in vivo.

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    Ashish Tandon

    Full Text Available This study examined the effects of BMP7 gene transfer on corneal wound healing and fibrosis inhibition in vivo using a rabbit model. Corneal haze in rabbits was produced with the excimer laser performing -9 diopters photorefractive keratectomy. BMP7 gene was introduced into rabbit keratocytes by polyethylimine-conjugated gold nanoparticles (PEI2-GNPs transfection solution single 5-minute topical application on the eye. Corneal haze and ocular health in live animals was gauged with stereo- and slit-lamp biomicroscopy. The levels of fibrosis [α-smooth muscle actin (αSMA, F-actin and fibronectin], immune reaction (CD11b and F4/80, keratocyte apoptosis (TUNEL, calcification (alizarin red, vonKossa and osteocalcin, and delivered-BMP7 gene expression in corneal tissues were quantified with immunofluorescence, western blotting and/or real-time PCR. Human corneal fibroblasts (HCF and in vitro experiments were used to characterize the molecular mechanism mediating BMP7's anti-fibrosis effects. PEI2-GNPs showed substantial BMP7 gene delivery into rabbit keratocytes in vivo (2×10(4 gene copies/ug DNA. Localized BMP7 gene therapy showed a significant corneal haze decrease (1.68±0.31 compared to 3.2±0.43 in control corneas; p88%; p<0.0001, and immunoblotting of BMP7-transefected HCFs grown in the presence of TGFβ demonstrated significantly enhanced pSmad-1/5/8 (95%; p<0.001 and Smad6 (53%, p<0.001, and decreased αSMA (78%; p<0.001 protein levels. These results suggest that localized BMP7 gene delivery in rabbit cornea modulates wound healing and inhibits fibrosis in vivo by counter balancing TGFβ1-mediated profibrotic Smad signaling.

  1. A new paradigm for use of ultrafast lasers in ophthalmology for enhancement of corneal mechanical properties and permanent correction of refractive errors

    Science.gov (United States)

    Wang, Chao; Fomovsky, Mikhail; Hall, Jamie R.; Paik, David C.; Trokel, Stephen L.; Vukelic, Sinisa

    2017-02-01

    A new paradigm for strengthening of corneal tissue as well as permanent correction of refractive errors has been proposed. Ultrafast laser irradiation is confined to the levels below optical breakdown such that tissue damage is avoided while creating an ionization field responsible for subsequent photochemical modification of the stroma. The concept was assed using newly developed platform for precise application of a near-IR femtosecond laser irradiation to the cornea in in-vitro experiments. Targeted irradiation with tightly focused ultrafast laser pulses allows spatially resolved crosslinking in the interior of the porcine cornea in the absence of photosensitizers. The formation of intra- or interstromal covalent bonds in collagen matrix locally increases lamellar density. Due to high resolution, treatment is spatially resolved and therefore can be tailored to either enhance structure of corneal stroma or adjust corneal curvature towards correcting refractive errors. As the induced modification is primarily driven by nonlinear absorption, the treatment is essentially wavelength independent, and as such potentially less harmful than current method of choice, joint application of UVA light irradiation in conjunction with riboflavin. Potential applicability of a near-IR femtosecond laser for biomechanical stabilization of cornea and non-invasive refractive eye corrections is discussed.

  2. Femtosecond laser-assisted lamellar keratoplasty (FSLK) for anterior corneal stromal diseases.

    Science.gov (United States)

    Almousa, Radwan; Samaras, Konstantinos E; Khan, Saj; Lake, Damian B; Daya, Sheraz M

    2014-02-01

    Our objective was to study the outcome of femtosecond-assisted lamellar keratoplasty (FSLK) in stromal corneal diseases. This is a retrospective chart review of 17 patients (20 eyes) who underwent FSLK for anterior corneal pathologies. Main outcome measures were refractive results following FSLK, complications, and graft survival. Mean follow-up time was 42 ± 15 (7-58) months. Preoperative best spectacle-corrected visual acuity (BSCVA) was ≤20/40 in 17 eyes. Postoperative BSCVA ≥ 20/40 was achieved in 12/14 at 12 months, 11/12 at 24 months, and 10/12 eyes at 36 months; postoperative BSCVA ≥ 20/25 was achieved in 8/14, 8/12, and 5/12 eyes at 12, 24, and 36 months, respectively. One eye had vertical gas break through the epithelium during the FSLK. One eye had postoperative epithelial rejection and two eyes had stromal rejection treated successfully with topical steroids. Another eye had epithelial ingrowth that was not progressive; however, the same eye developed bacterial keratitis and scarred graft 32 months post-FSLK. One eye had graft dehiscence and one eye developed excessive interface fibrosis. Five out of 20 grafts failed due to the recurrence of the original disease (3), corneal scarring (1), and excessive interface fibrosis (1). FSLK provides many advantages over conventional PK and DALK, with faster visual rehabilitation and emmetropization of the manifest refraction rather than inducing ametropia and irregular astigmatism.

  3. Postoperative Efficacy, Predictability, Safety, and Visual Quality of Laser Corneal Refractive Surgery: A Network Meta-analysis.

    Science.gov (United States)

    Wen, Daizong; McAlinden, Colm; Flitcroft, Ian; Tu, Ruixue; Wang, Qinmei; Alió, Jorge; Marshall, John; Huang, Yingying; Song, Benhao; Hu, Liang; Zhao, Yune; Zhu, Senmiao; Gao, Rongrong; Bao, Fangjun; Yu, Ayong; Yu, Ye; Lian, Hengli; Huang, Jinhai

    2017-06-01

    To compare the postoperative efficacy, predictability, safety, and visual quality of all major forms of laser corneal refractive surgeries for correcting myopia. Systematic review and network meta-analysis. Search of MEDLINE, EMBASE, Cochrane Library, and the US trial registry was conducted up to November 2015. Randomized controlled trials (RCT) reporting in accordance with the eligibility criteria were included in this review. We performed a Bayesian random-effects network meta-analysis. Forty-eight RCTs were identified. For efficacy (uncorrected visual acuity [UCVA]), there were no statistically significant differences between any pair of treatments analyzed. The SUCRA (surface under the cumulative ranking curve) ranking (from best to worst) was femtosecond-based laser in situ keratomileusis (FS-LASIK), LASIK, small-incision lenticule extraction, femtosecond lenticule extraction (FLEx), photorefractive keratectomy (PRK), laser epithelial keratomileusis (LASEK), epipolis (Epi)-LASIK, transepithelial PRK (T-PRK). For predictability (refractive spherical equivalent [SE]), a statistically significant difference was found when FS-LASIK was compared with LASIK (odds ratio [OR] 2.29, 95% credible interval [CrI] 1.20-4.14), PRK (OR 2.16, 95% CrI 1.15-4.03), LASEK (OR 2.09, 95% CrI 1.08-4.55), and Epi-LASIK (OR 2.74, 95% CrI 1.11-6.20). The SUCRA ranking (from best to worst) was FS-LASIK, T-PRK, LASEK, PRK, LASIK, Epi-LASIK. There were no statistically significant differences in the safety (best spectacle-corrected visual acuity) comparisons. For both postoperative higher-order aberrations (HOAs) and contrast sensitivity (CS), there were no statistically significant differences between any pair of treatments analyzed. The SUCRA ranking results show that some corneal surface ablation techniques (PRK and LASEK) rank highest. This network meta-analysis shows that there were no statistically significant differences in either visual outcomes (efficacy and safety) or visual

  4. Choice of the laser wavelength for a herpetic keratitis treatment

    Science.gov (United States)

    Razhev, Alexander M.; Bagayev, Sergei N.; Chernikh, Valery V.; Kargapoltsev, Evgeny S.; Trunov, Alexander; Zhupikov, Andrey A.

    2002-06-01

    For the first time the effect of the UV laser radiation to human eye cornea with herpetic keratitis was experimentally investigated. In experiments the UV radiation of ArF (193 nm), KrCl (223 nm), KrF (248 nm) excimer lasers were used. Optimal laser radiation parameters for the treatment of the herpetic keratitis were determined. The immuno-biochemical investigations were carried out and the results of clinical trials are presented. The maximum ablation rate was obtained for the 248 nm radiation wavelength. The process of healing was successful but in some cases the haze on the surface of the cornea was observed. When used the 193 nm radiation wavelength the corneal surface was clear without any hazes but the epithelization process was slower than for 248 nm wavelength and in some cases the relapse was occurred. The best results for herpetic keratitis treatment have been achieved by utilizing the 223 nm radiation wavelength of the KrCl excimer laser. The use of the 223 nm radiation wavelength allows treating the herpetic keratitis with low traumatic process of ablation and provides high quality of corneal surface.

  5. Intrastromal refractive sugery with ultrashort laser pulses in living animals

    Science.gov (United States)

    Heisterkamp, Alexander; Mamom, Thanongsak; Kermani, Omid; Drommer, Wolfgang; Welling, Herbert; Ertmer, Wolfgang; Lubatschowski, Holger

    2002-06-01

    In order to perform refractive surgery, fs-laser pulses of 130-fs pulse duration were focused into animal cornea. By focusing the radiation down to spot-sizes of 5 micrometers , very precise cuts could be achieved inside the treated eyes, accompanied with minimum collateral damage to the tissue by thermal or mechanical effects. Due to these low side effects, micrometers -cutting precisions at preparing of corneal flaps and lenticules can be achieved. Thus, animal studies with 8 living rabbits were performed, in which intrastromal lenticules and flaps were created and extracted. Wound healing reactions were studied by histo- pathological analysis of the treated eyes in intervals at one, 7, 14 and 28 days after surgery. The treated eyes showed mild wound healing reactions with comparable results to what is known from Excimer-LASIK. Moreover the use of the fs-laser offered new possibilities in preparation of corneal flaps, providing advantages to the use of the mechanical keratome.

  6. Application of ultrashort laser pulses for intrastromal refractive surgery.

    Science.gov (United States)

    Lubatschowski, H; Maatz, G; Heisterkamp, A; Hetzel, U; Drommer, W; Welling, H; Ertmer, W

    2000-01-01

    Recently, laser systems have become available which generate ultrashort laser pulses with a duration of 100-200 femtoseconds (fs). By generating micro-plasmas inside the corneal stroma with fs pulses, it is possible to achieve a cutting effect inside the tissue while leaving the anterior layers intact. The energy threshold to generate a micro-plasma with fs pulses is some orders of magnitude lower than it is for picosecond or nanosecond pulses. This results in a strong reduction of the thermal and mechanical damage of the surrounding tissue. With a titanium:sapphire fs laser system, the cutting effect on corneal tissue from freshly enucleated porcine eye globes was investigated with different pulse energies. The irradiated samples were examined by light and electron microscopy. The laser-induced pressure transients and the laser-induced bubble formation were analysed with a broadband acoustic transducer and by flash photography. With fs laser pulses, the extent of thermal and mechanical damage of the adjacent tissue is in the order of 1 microm or below and therefore comparable with the tissue alterations after ArF excimer laser ablation. Using pulse energies of approximately 1-2 microJ and a spot diameter of 5-10 microm, intrastromal cuts can be performed very precisely in order to prepare corneal flaps and lenticules. Femtosecond photodisruption has the potential to become an attractive tool for intrastromal refractive surgery.

  7. Transepithelial Phototherapeutic Keratectomy Using a 213-nm Solid-State Laser System Followed by Corneal Collagen Cross-Linking with Riboflavin and UVA Irradiation

    Directory of Open Access Journals (Sweden)

    George D. Kymionis

    2010-01-01

    Full Text Available Purpose. To present a case of a keratoconic patient who underwent epithelial removal with transepithelial phototherapeutic keratectomy (t-PTK using a 213-nm solid-state laser system followed by corneal collagen cross-linking (CXL with riboflavin and ultraviolet-A (UVA irradiation. Methods. Case report. Results. A twenty-four-year-old male with keratoconus underwent CXL treatment after epithelial removal with t-PTK using a solid-state laser system. No intra- or early postoperative complications were found. One month postoperatively, uncorrected visual acuity (UCVA improved from 20/63 to 20/32 while best spectacle- corrected visual acuity (BSCVA improved from 20/40 to 20/25. Corneal topography revealed a significant improvement which remained stable during the six-month followup period. Conclusions. Epithelial removal with t-PTK before CXL could improve patient's visual outcome.

  8. [Corneal biomechanics: Corvis® ST parameters after LASIK].

    Science.gov (United States)

    Frings, A; Linke, S J; Bauer, E L; Druchkiv, V; Katz, T; Steinberg, J

    2015-09-01

    Corneal refractive surgery alters the biomechanical properties of the cornea. This study was initiated to evaluate corneal biomechanical parameters after LASIK using a Corvis® ST tonometer (CST). This retrospective study included 51 eyes of 32 myopic 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 second applanation length, mean first and second deflection lengths, mean first and second deflection amplitudes, peak distance and radius of curvature. Statistically significant positive correlations were found between the change (Δ) in radius of curvature and Δ in manifest refraction spherical equivalent (MRSE), between the ablation depth and the Δ in intraocular pressure. Applying multiple regression models also revealed statistically significant differences in parameters obtained by CST measurements. 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.

  9. Laser corneal refractive surgery in the twenty-first century: a review of the impact of refractive surgery on high-order aberrations (and vice versa)

    Science.gov (United States)

    Arba-Mosquera, Samuel; Arbelaez, Maria C.; de Ortueta, Diego

    2010-07-01

    Here we review the situation of laser corneal refractive surgery in the twenty-first century. We pay special attention to the change in aberrations, covering the compensation of the loss of ablation efficiency at non-normal incidence, the effects of cyclotorsional errors, aspheric, wavefront optimized and aberration neutral concepts, and centration of refractive profiles. A review of the clinical outcomes is provided including myopic, hyperopic, and astigmatic, as well as wavefront customized or presbyopic outcomes.

  10. [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.

  11. 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.

  12. Detection of Progressive Retinal Nerve Fiber Layer Loss in Glaucoma Using Scanning Laser Polarimetry with Variable Corneal Compensation

    Science.gov (United States)

    Medeiros, Felipe A.; Alencar, Luciana M.; Zangwill, Linda M.; Bowd, Christopher; Vizzeri, Gianmarco; Sample, Pamela A.; Weinreb, Robert N.

    2010-01-01

    Purpose To evaluate the ability of scanning laser polarimetry with variable corneal compensation to detect progressive retinal nerve fiber layer (RNFL) loss in glaucoma patients and patients suspected of having the disease. Methods This was an observational cohort study that included 335 eyes of 195 patients. Images were obtained annually with the GDx VCC scanning laser polarimeter, along with optic disc stereophotographs and standard automated perimetry (SAP) visual fields. The median follow-up time was 3.94 years. Progression was determined using commercial software for SAP and by masked assessment of optic disc stereophotographs performed by expert graders. Random coefficient models were used to evaluate the relationship between RNFL thickness measurements over time and progression as determined by SAP and/or stereophotographs. Results From the 335 eyes, 34 (10%) showed progression over time by stereophotographs and/or SAP. Average GDx VCC measurements decreased significantly over time for both progressors as well as non-progressors. However, the rate of decline was significantly higher in the progressing group (−0.70 μm/year) compared to the non-progressing group (−0.14 μm/year; P = 0.001). Black race and male sex were significantly associated with higher rates of RNFL loss during follow-up. Conclusions The GDx VCC scanning laser polarimeter was able to identify longitudinal RNFL loss in eyes that showed progression in optic disc stereophotographs and/or visual fields. These findings suggest that this technology could be useful to detect and monitor progressive disease in patients with established diagnosis of glaucoma or suspected of having the disease. PMID:19029038

  13. [Infectious corneal ulcers--once with endophthalmitis--after photorefractive keratotomy with disposable contact lens].

    Science.gov (United States)

    Faschinger, C; Faulborn, J; Ganser, K

    1995-02-01

    Infections of the cornea with or without involvement of intraocular tissues are severe complications after photorefractive keratectomy. We report on three cases with ulcerative keratitis and one case with severe endophthalmitis, which developed some days after laser treatment. After 39 photo-therapeutic and 118 photo-refractive treatments without complications four young treated persons suffered from corneal infiltrations. Three of them developed severe corneal ulcerations, one a severe endophthalmitis. We used the laser machine of the company Schwind (193 nm wavelength, repetition rate 10 Hz, fluence 180-200 mJ/cm2). One part of the treatment which all patients had in common was the application of a disposable contact lens postoperatively, which was worn overnight. THERAPY AND FOLLOW-UP: Because all three patients with ulcerations revealed hyphen of fungi in their corneal-scratch material they were treated with antifungal agents locally and systemically. Due to the local and temporal connection the patient with the endophthalmitis was treated with antifungal agents, too. All corneal ulcerations healed with scars similar to a haze graded 3 to 4, the eye with the endophthalmitis healed almost completely. Probably the use of disposable contact lenses postoperatively, especially the overnight wear, during an extremely hot and humid summer lead to the described severe infections of the eyes after the "traumatisation" of the cornea by the excimer laser. A known higher concentration of Aspergillus in the air due to renovations of buildings in the clinical area might have been an additional negative effect. The avoidance of the use of disposable contact lenses postoperatively, especially the overnight wear, is emphasized.

  14. Clinical results of 123 femtosecond laser-assisted penetrating keratoplasties.

    Science.gov (United States)

    Birnbaum, Florian; Wiggermann, Antonia; Maier, Philip C; Böhringer, Daniel; Reinhard, Thomas

    2013-01-01

    Postoperative astigmatism following penetrating keratoplasty is a major problem after corneal transplantation. The main goal of new trephination techniques such as femtosecond laser or excimer-laser trephination is to improve refractive and visual outcomes. The femtosecond laser technique makes profiled corneal trephinations such as the top hat or mushroom profile possible. We present the postoperative outcome of femtosecond laser-assisted penetrating keratoplasties. We performed 123 femtosecond laser-assisted penetrating keratoplasties in 119 patients. The main outcome measures were intraoperative specifics, astigmatism, and irregularity in Orbscan corneal topography, as well as the occurrence of immune reactions and side-effects. All sutures have been removed in 49 of these 123 eyes. Their mean follow-up was 13.9 ± 4.5 months. Time to complete suture removal (n = 49) was 12.0 ± 3.7 months in the mushroom group and 9.8 ± 2.1 months in the top hat group. Mean astigmatism in Orbscan topography was 6.4 ± 3.0 diopters in the mushroom and 5.8 ± 4.6 diopters in the top hat group (all sutures out). Femtosecond laser-assisted penetrating keratoplasty is a safe surgical technique. Due to the steps in profiled trephinations, the wound area is larger and theoretically the wound healing is, thus, faster and more stable. Complete suture removal is possible at an earlier time point compared to conventional penetrating keratoplasty. However, refractive results are not superior to those following conventional trephination.

  15. Evaluation of Corneal Cross-Linking for Treatment of Fungal Keratitis: Using Confocal Laser Scanning Microscopy on an Ex Vivo Human Corneal Model.

    Science.gov (United States)

    Alshehri, Jawaher M; Caballero-Lima, David; Hillarby, M Chantal; Shawcross, Susan G; Brahma, Arun; Carley, Fiona; Read, Nick D; Radhakrishnan, Hema

    2016-11-01

    Some previous reports have established the use of photoactivated chromophore-induced corneal cross-linking (PACK-CXL) in treating fungal keratitis. The results of these case reports have often been conflicting. To systematically study the effect of PACK-CXL in the management of Fusarium keratitis, we have developed an ex vivo model of human corneal infection using eye-banked human corneas. Sixteen healthy ex vivo human corneas were divided into four study groups: (1) untreated control, (2) cross-linked, (3) infected with fungal spores, and (4) infected with fungal spores and then cross-linked. All infected corneas were inoculated with Fusarium oxysporum spores. The PACK-CXL procedure was performed 24 hours post inoculation for group 4. For PACK-CXL treatment, the corneas were debrided of epithelium; then 1% (wt/vol) isotonic riboflavin was applied dropwise at 5-minute intervals for 30 minutes and during the course of UV-A cross-linking for another 30 minutes. The corneas were imaged using a confocal microscope at 48 hours post inoculation, and the Fusarium hyphal volume and spore concentration were calculated. The infected and then cross-linked group had a significantly lower volume of Fusarium hyphae, compared to the infected (P = 0.001) group. In the infected and then cross-linked group there was significant inhibition of Fusarium sporulation compared with the infected (P = 0.007) group. A model of human corneal infection was successfully developed for investigation of the effects of PACK-CXL on fungal keratitis. A treatment regimen of combined UV-A/riboflavin-induced corneal cross-linking appears to be a valuable approach to inhibit the growth and sporulation of Fusarium and suppress the progression of fungal keratitis.

  16. Corneal Laceration

    Medline Plus

    Full Text Available ... or apply pressure to eye avoid giving aspirin, ibuprofen or other non-steroidal, anti-inflammatory drugs. These ... lost sight from a corneal scar as a child. Now that I’m older, will a corneal ...

  17. Corneal Laceration

    Medline Plus

    Full Text Available ... rub or apply pressure to eye avoid giving aspirin, ibuprofen or other non-steroidal, anti-inflammatory drugs. ... lost sight from a corneal scar as a child. Now that I’m older, will a corneal ...

  18. Corneal Laceration

    Medline Plus

    Full Text Available ... Now that I’m older, will a corneal transplant help me? May 15, 2015 Why Do My ... May Have A Future Alternative to Full Corneal Transplantation Nov 29, 2016 Combating Eye Injuries from Air ...

  19. Analysis of seasonal changes in residual refraction 1-year after corneal laser refractive surgery: a retrospective study.

    Science.gov (United States)

    Luger, Michiel H A; Ewering, Tobias; Arba-Mosquera, Samuel

    2014-01-01

    To analyze the effect of seasonal changes in residual refraction 1-year after corneal refractive surgery using the SCHWIND AMARIS laser system. 5740 consecutive treatments have been retrospectively reviewed. For all eyes, aspheric treatments were planned with the Custom Ablation Manager software and the ablations were performed with the SCHWIND AMARIS system (SCHWIND eye-tech-solutions). Seasonal outcomes were evaluated in terms of residual refraction stratified per treatment month, as well as stratified per year season. Student's T test comparing stratified values with global ones was used for the statistical analysis. Treatments performed in April, June, August, September, and October showed relative undercorrections of the spherical equivalent (SE) (-0.09D), whereas treatments performed in January, February, and March showed relative overcorrections of the SE (+0.13D). Similarly, treatments performed in spring and summer showed relative undercorrections of the SE (-0.04D), whereas treatments performed in winter showed relative overcorrections of the SE (+0.10D). Seasonal differences in refractive outcomes were observed among a large scale population. The effect of these environmental variables on refractive outcomes warrants further evaluation. Copyright © 2013 Spanish General Council of Optometry. Published by Elsevier Espana. All rights reserved.

  20. 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

  1. Computational Model for Corneal Transplantation

    Science.gov (United States)

    Cabrera, Delia

    2003-10-01

    We evaluated the refractive consequences of corneal transplants using a biomechanical model with homogeneous and inhomogeneous Young's modulus distributions within the cornea, taking into account ablation of some stromal tissue. A FEM model was used to simulate corneal transplants in diseased cornea. The diseased cornea was modeled as an axisymmetric structure taking into account a nonlinearly elastic, isotropic formulation. The model simulating the penetrating keratoplasty procedure gives more change in the postoperative corneal curvature when compared to the models simulating the anterior and posterior lamellar graft procedures. When a lenticle shaped tissue was ablated in the graft during the anterior and posterior keratoplasty, the models provided an additional correction of about -3.85 and -4.45 diopters, respectively. Despite the controversy around the corneal thinning disorders treatment with volume removal procedures, results indicate that significant changes in corneal refractive power could be introduced by a corneal transplantation combined with myopic laser ablation.

  2. Corneal first-surface aberration analysis of the biomechanical effects of astigmatic keratotomy and a microkeratome cut after penetrating keratoplasty.

    Science.gov (United States)

    Kohnen, Thomas; Bühren, Jens

    2005-01-01

    Astigmatic keratotomy (AK) was performed in a patient after penetrating keratoplasty (PKP) for keratoconus to reduce high post-PKP astigmatism. The procedure led to a significant decrease in astigmatism, but corneal higher-order aberrations (HOAs) increased. After PKP, the patient was scheduled for 2-step laser in situ keratomileusis (LASIK) to correct myopia and astigmatism. One day after the microkeratome cut, a decrease of -2.75 diopters in the spherical equivalent (SE) was noted. Although subjective manifest cylinder and corneal spherical aberrations were marginally affected, a marked decrease in coma and other HOAs could be observed. One month after the cut, the SE was unchanged. Excimer laser ablation was not performed as the patient was satisfied with the result and refused further treatment. This case shows that AK cuts can induce HOAs and a single microkeratome cut performed in corneal grafts can have strong biomechanical effects on lower-order aberrations and HOAs. If LASIK is planned after PKP, a 2-step approach is recommended to anticipate biomechanical effects and avoid overcorrection or undercorrection.

  3. Corneal dystrophies

    Directory of Open Access Journals (Sweden)

    Klintworth Gordon K

    2009-02-01

    Full Text Available Abstract The term corneal dystrophy embraces a heterogenous group of bilateral genetically determined non-inflammatory corneal diseases that are restricted to the cornea. The designation is imprecise but remains in vogue because of its clinical value. Clinically, the corneal dystrophies can be divided into three groups based on the sole or predominant anatomical location of the abnormalities. Some affect primarily the corneal epithelium and its basement membrane or Bowman layer and the superficial corneal stroma (anterior corneal dystrophies, the corneal stroma (stromal corneal dystrophies, or Descemet membrane and the corneal endothelium (posterior corneal dystrophies. Most corneal dystrophies have no systemic manifestations and present with variable shaped corneal opacities in a clear or cloudy cornea and they affect visual acuity to different degrees. Corneal dystrophies may have a simple autosomal dominant, autosomal recessive or X-linked recessive Mendelian mode of inheritance. Different corneal dystrophies are caused by mutations in the CHST6, KRT3, KRT12, PIP5K3, SLC4A11, TACSTD2, TGFBI, and UBIAD1 genes. Knowledge about the responsible genetic mutations responsible for these disorders has led to a better understanding of their basic defect and to molecular tests for their precise diagnosis. Genes for other corneal dystrophies have been mapped to specific chromosomal loci, but have not yet been identified. As clinical manifestations widely vary with the different entities, corneal dystrophies should be suspected when corneal transparency is lost or corneal opacities occur spontaneously, particularly in both corneas, and especially in the presence of a positive family history or in the offspring of consanguineous parents. Main differential diagnoses include various causes of monoclonal gammopathy, lecithin-cholesterol-acyltransferase deficiency, Fabry disease, cystinosis, tyrosine transaminase deficiency, systemic lysosomal storage

  4. Corneal collagen cross-linking combined with simulation of femtosecond laser-assisted refractive lens extraction: an ex vivo biomechanical effect evaluation.

    Science.gov (United States)

    Kanellopoulos, Anastasios J; Kontos, Mark A; Chen, Shihao; Asimellis, George

    2015-05-01

    To evaluate biomechanical changes induced by in situ corneal cross-linking (CXL) with stromal pocket delivered enhanced concentration riboflavin and high-fluence, high-energy UV-A irradiation. Eight human donor corneas were subjected to intrastromal lamellar corneal tissue removal of anterior 140-μm deep, 80-μm thick × 5-mm diameter central stromal buttons, extracted through a 3.5-mm width tunnel, surfacing in the superior cornea periphery. Enhanced concentration riboflavin solution (0.25%) was instilled in the pocket. In study group A (CXL), superficial high-fluence UV-A irradiation was applied, whereas in control group B (no CXL), none. To comparatively assess changes in corneal rigidity, corneal specimens were subjected to transverse biaxial resistance measurements by application of a unidirectional tangential shear force. Biomechanical differences were evaluated through stress and Young shear modulus. Stress at 10% strain was 305 ± 24 kPa in study group A versus 157 ± 11 kPa in control group B (relative difference Δ = 107%, P = 0.021). Stress at 20% strain was 1284 ± 34 kPa in study group A versus 874 ± 29 kPa in control group B (Δ = 47%, P = 0.043). Average shear modulus in study group A at 10% strain was 6.98 ± 1.12 MPa versus 4.04 ± 0.85 MPa in control group B (Δ = 73%, P = 0.036). Average shear modulus in study group A at 20% strain was 11.46 ± 0.75 MPa versus 8.80 ± 0.72 MPa in group B (Δ = 30%, P = 0.047). Adjunct CXL in this ex vivo simulation refractive lens extraction procedure seems to provide significant increase in corneal rigidity, up to +107%. These findings also support our previous reported work on laser in situ keratomileusis combined with CXL.

  5. Imaging Mass Spectrometry by Matrix-Assisted Laser Desorption/Ionization and Stress-Strain Measurements in Iontophoresis Transepithelial Corneal Collagen Cross-Linking

    Directory of Open Access Journals (Sweden)

    Paolo Vinciguerra

    2014-01-01

    Full Text Available Purpose. To compare biomechanical effect, riboflavin penetration and distribution in transepithelial corneal collagen cross-linking with iontophoresis (I-CXL, with standard cross linking (S-CXL and current transepithelial protocol (TE-CXL. Materials and Methods. The study was divided into two different sections, considering, respectively, rabbit and human cadaver corneas. In both sections corneas were divided according to imbibition protocols and irradiation power. Imaging mass spectrometry by matrix-assisted laser desorption/ionization (MALDI-IMS and stress-strain measurements were used. Forty-eight rabbit and twelve human cadaver corneas were evaluated. Results. MALDI-IMS showed a deep riboflavin penetration throughout the corneal layers with I-CXL, with a roughly lower concentration in the deepest layers when compared to S-CXL, whereas with TE-CXL penetration was considerably less. In rabbits, there was a significant increase (by 71.9% and P=0.05 in corneal rigidity after I-CXL, when compared to controls. In humans, corneal rigidity increase was not significantly different among the subgroups. Conclusions. In rabbits, I-CXL induced a significant increase in corneal stiffness as well as better riboflavin penetration when compared to controls and TE-CXL but not to S-CXL. Stress-strain in human corneas did not show significant differences among techniques, possibly because of the small sample size of groups. In conclusion, I-CXL could be a valid alternative to S-CXL for riboflavin delivery in CXL, preserving the epithelium.

  6. The effect of humidity and temperature on visual outcomes after myopic corneal laser refractive surgery.

    Science.gov (United States)

    Hood, Christopher T; Shtein, Roni M; Veldheer, Daniel; Hussain, Munira; Niziol, Leslie M; Musch, David C; Mian, Shahzad I

    2016-01-01

    To determine whether procedure room environmental conditions are associated with outcomes after myopic laser in situ keratomileusis (LASIK) or laser-assisted keratomileusis (LASEK). Retrospective chart review. Eight hundred sixty-three eyes of 458 consecutive patients at a university-based academic practice. We reviewed the medical records of consecutive patients who underwent LASIK or LASEK over a 3-year period. Linear mixed regression models were used to investigate the association of laser room temperature and humidity with the outcomes of visual acuity and postoperative manifest spherical equivalent refraction. Repeated measures logistic regression models were used for the outcomes of diffuse lamellar keratitis (DLK) and need for enhancement surgery. Subjects were on an average 38.6 years old at the time of surgery (standard deviation [SD] =10.3) and the average spherical equivalent refraction of eyes was 3.8 diopters (SD =2.03). Regression models did not reveal a significant association between temperature and uncorrected distance visual acuity (UDVA) or corrected distance visual acuity (CDVA), or between humidity and UDVA (P>0.05 for all). However, increased humidity was associated with a small but statistically significant improvement in CDVA after LASIK at 1 day, 1 month, 3 months, and 1 year postoperatively (Prefraction. While increased laser room humidity was consistently associated with small improvements in CDVA after myopic LASIK over time, variations in room temperature and humidity were not associated with UDVA, the need for enhancement, the incidence of DLK, or refraction after myopic LASIK or LASEK.

  7. Amniotic membrane transplantation in corneal melting after anterior lamellar keratoplasty assisted by femtosecond laser in children.

    Science.gov (United States)

    Buzzonetti, Luca; Petrocelli, Gianni; Valente, Paola

    2012-01-01

    To evaluate the efficacy of amniotic membrane transplantation in lamella melting after anterior lamellar keratoplasty (ALK) assisted by femtosecond laser in a pediatric patient. An 11-year-old girl with progressive keratoconus underwent ALK assisted by femtosecond laser on the right eye. The surgical procedure was performed under general anesthesia. The 60-KHz IntraLase femtosecond laser (Abbott Medical Optics) created both the donor (thickness 350 µm; diameter 8.1 mm; side cut 70°) and recipient (thickness 260 µm; diameter 8.0 mm; side cut 70°) lamellae. The recipient lamella was then gently removed and donor was fitted into place and sutured using 4 interrupted sutures added to a running suture in nylon 10-0. The surgery was uneventful. Two months after surgery, a lamella melting was observed. One month after topical steroid treatment, amniotic membrane transplantation was performed. When lamella melting was observed, the best-corrected visual acuity (BCVA) was 0.1 and 0.5 with foramen and no inflammatory reaction in the anterior chamber was reported. Eleven months after amniotic membrane transplantation, BCVA was 0.9 and no visual acuity increase was recorded with foramen. Our findings show that amniotic membrane transplantation could be considered in lamella melting after ALK assisted by femtosecond laser in children.

  8. Femtosecond laser refractive surgery: small-incision lenticule extraction vs. femtosecond laser-assisted LASIK.

    Science.gov (United States)

    Lee, Jimmy K; Chuck, Roy S; Park, Choul Yong

    2015-07-01

    Small-incision lenticule extraction (SMILE) is a novel technique devised to correct refractive errors. SMILE circumvents excimer laser photoablation of cornea, as the stromal lenticule cut by femtosecond laser is removed manually. Smaller incisions and preservation of anterior corneal biomechanical strength have been suggested as some of the advantages of SMILE over femtosecond laser-assisted LASIK (FS-LASIK). In this review, we compared previous published results of SMILE and FS-LASIK. The advantage, efficacy and safety of SMILE are compared with FS-LASIK. SMILE achieved similar efficacy, predictability and safety as FS-LASIK. Greater preservations of corneal biomechanical strength and corneal nerves were observed in SMILE when compared with LASIK or PRK. Additionally, the incidence of postoperative dry eye syndrome was found to be less problematic in SMILE than in FS-LASIK. SMILE is a promising new surgery for refractive error correction. Prospective and retrospective studies of SMILE have shown that results of SMILE are similar to FS-LASIK. With advances in femtosecond laser technology, SMILE may gain greater acceptance in the future.

  9. [Comparison of Lasik with femtosecond laser versus Lasik with mechanical microkeratome: predictability of flap depth, corneal biomechanical effects and optical aberrations].

    Science.gov (United States)

    Kouassi, F-X; Blaizeau, M; Buestel, C; Schweitzer, C; Gallois, A; Colin, J; Touboul, D

    2012-01-01

    To compare the predictability of flap thickness, high-order optic aberrations (HOAs), and biomechanical properties of cornea between patients treated by Lasik with mechanical microkeratome versus patients treated by FemtoLasik. Department of ophthalmology, Pellegrin University Hospital, Bordeaux, France. We conducted a retrospective study on 53 myopic patients who underwent Lasik with either mechanical microkeratome (MK group) or femtosecond laser (FS group). Refraction, central corneal thickness, high-order optic aberrations (HOAs), corneal hysteresis (CH), and corneal resistance factor (CRF), were analysed pre- and postoperatively in both groups. The central corneal thickness was measured with OCT-Visante(®) (Carl-Zeiss, Meditec), biomechanical parameters with ORA(®) (Reichert), and optical aberrations with the Wave Scan(®) (AMO) aberrometer. We included 44 eyes of 22 patients in the MK group and 62 eyes of 31 patients in the FS group. Preoperatively, the mean best-corrected visual acuity was 0.95 in both groups. In the MK group, the flap was significantly thicker than expected (162/130 μm), but in the FS group, there was no significant difference (117/120 μm). The biomechanical properties of the cornea were lower in both groups independently of the flap cutting technique. The HOAs increased after Lasik and were not influenced by the flap cutting technique. Neither mechanical microkeratome, nor femtosecond laser for flap creation, increases HOAs and the biomechanical changes of the cornea, according to ORA(®), significantly after Lasik. Copyright © 2011 Elsevier Masson SAS. All rights reserved.

  10. 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...

  11. Laser-induced corneal cross-linking upon photorefractive ablation with riboflavin

    OpenAIRE

    Kornilovskiy IM; Kasimov EM; Sultanova AI; Burtsev AA

    2016-01-01

    Igor M Kornilovskiy,1 Elmar M Kasimov,2 Ayten I Sultanova,2 Alexander A Burtsev1 1Department of Eye Diseases, Federal State Budgetary Institution “National Pirogov Medical Surgical Centre”, Ministry of Health, Moscow, Russia; 2Department of Eye Diseases, Zarifa Aliyeva National Ophthalmology Center, Ministry of Health, Baku, Azerbaijan Aim: To estimate the biomechanical effect of the laser-induced cross-linking resulting from photorefractive ablation of the cornea with r...

  12. 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.

  13. The effect of humidity and temperature on visual outcomes after myopic corneal laser refractive surgery

    Directory of Open Access Journals (Sweden)

    Hood CT

    2016-11-01

    Full Text Available Christopher T Hood,1 Roni M Shtein,1 Daniel Veldheer,1,2 Munira Hussain,1 Leslie M Niziol,1 David C Musch,1,3 Shahzad I Mian1 1Department of Ophthalmology and Visual Sciences, University of Michigan W.K. Kellogg Eye Center, Ann Arbor, MI, 2Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, WI, 3Department of Epidemiology, University of Michigan, Ann Arbor, MI, USA Objective: To determine whether procedure room environmental conditions are associated with outcomes after myopic laser in situ keratomileusis (LASIK or laser-assisted keratomileusis (LASEK. Design: Retrospective chart review. Participants: Eight hundred sixty-three eyes of 458 consecutive patients at a university-based academic practice. Methods: We reviewed the medical records of consecutive patients who underwent LASIK or LASEK over a 3-year period. Linear mixed regression models were used to investigate the association of laser room temperature and humidity with the outcomes of visual acuity and postoperative manifest spherical equivalent refraction. Repeated measures logistic regression models were used for the outcomes of diffuse lamellar keratitis (DLK and need for enhancement surgery. Results: Subjects were on an average 38.6 years old at the time of surgery (standard deviation [SD] =10.3 and the average spherical equivalent refraction of eyes was 3.8 diopters (SD =2.03. Regression models did not reveal a significant association between temperature and uncorrected distance visual acuity (UDVA or corrected distance visual acuity (CDVA, or between humidity and UDVA (P>0.05 for all. However, increased humidity was associated with a small but statistically significant improvement in CDVA after LASIK at 1 day, 1 month, 3 months, and 1 year postoperatively (P<0.05 for all. There was no significant association between temperature and humidity and the need for enhancement, the incidence of DLK, or postoperative manifest refraction. Conclusion: While increased laser

  14. Atypical birefringence pattern and the diagnostic ability of scanning laser polarimetry with enhanced corneal compensation in glaucoma.

    Science.gov (United States)

    Rao, Harsha L; Yadav, Ravi K; Begum, Viquar U; Addepalli, Uday K; Senthil, Sirisha; Choudhari, Nikhil S; Garudadri, Chandra S

    2015-03-01

    To evaluate the effect of typical scan score (TSS), when within the acceptable limits, on the diagnostic performance of retinal nerve fibre layer (RNFL) parameters with the enhanced corneal compensation (ECC) protocol of scanning laser polarimetry (SLP) in glaucoma. In a cross-sectional study, 203 eyes of 160 glaucoma patients and 140 eyes of 104 control subjects underwent RNFL imaging with the ECC protocol of SLP. TSS was used to quantify atypical birefringence pattern (ABP) images. Influence of TSS on the diagnostic ability of SLP parameters was evaluated by receiver operating characteristic (ROC) regression models after adjusting for the effect of disease severity [based on mean deviation (MD)] on standard automated perimetry). Diagnostic abilities of all RNFL parameters of SLP increased when the TSS values were higher. This effect was statistically significant for TSNIT (coefficient: 0.08, p<0.001) and inferior average parameters (coefficient: 0.06, p=0.002) but not for nerve fibre indicator (NFI, coefficient: 0.03, p=0.21). In early glaucoma (MD of -5 dB), predicted area under ROC curve (AUC) for TSNIT average parameter improved from 0.642 at a TSS of 90 to 0.845 at a TSS of 100. In advanced glaucoma (MD of -15 dB), AUC for TSNIT average improved from 0.832 at a TSS of 90 to 0.947 at 100. Diagnostic performances of TSNIT and inferior average RNFL parameters with ECC protocol of SLP were significantly influenced by TSS even when the TSS values were within the acceptable limits. Diagnostic ability of NFI was unaffected by TSS values. © 2014 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

  15. Transplante de córnea com uso inadvertido de córnea de doador previamente submetido à cirurgia refrativa: relato de caso Corneal transplant utilizing a corneal graft that had undergone laser surgery: case report

    Directory of Open Access Journals (Sweden)

    Roberta Jansen de Mello Farias

    2005-04-01

    Full Text Available Relato de caso de paciente atendido no Departamento de Córnea do Hospital Oftalmológico de Sorocaba e submetido a transplante penetrante de córnea para correção de ceratocone no olho esquerdo. Foi utilizada córnea doadora previamente submetida a LASIK. A cirurgia foi completada sem intercorrências, embora durante o ato cirúrgico o cirurgião tenha percebido que havia um "flap" no botão doador. O paciente está no 6º mês pós-operatório com visão de 20/40 com correção. O PAM era de 20/40. Há epitélio na interface superior do "flap" sem sinais de progressão. Devem-se procurar novos métodos de avaliação de córneas doadoras; a utilização inadvertida de córnea doadora submetida a LASIK não interferiu até o 6º mês pós-operatório no resultado final do transplante; acompanhamento prolongado é necessário para avaliar a transparência e evolução da ceratometria e erro refracional deste transplante a longo prazo.Report on a successful clinical case of a corneal penetrating keratoplasty using inadvertently a corneal graft that had undergone laser assisted in situ keratomileusis (LASIK. Review of a clinical case of a patient of the Cornea Department of the "Hospital Oftalmológico de Sorocaba" who underwent a penetrating keratoplasty (PK to correct keratoconus in his left eye. A corneal graft from a donor who had LASIK surgery was used. Surgery was completed without complications, although a separation of the corneal lamellae was noted during surgery. Patient evolution was good with a final corrected visual acuity of 20/40. PAM was also 20/40. Epithelial growth was noticed on the flap interface, although, without progression of this finding. Eye Banks should improve screening techniques to rule out refractive surgery in the donor corneas; there was no impairment of the final result of this transplant until the 6th month after surgery; long-term follow-up is necessary to reveal if surgical success was impaired by prior

  16. Preloaded refractive-addition corneal inlay to compensate for presbyopia implanted using a femtosecond laser: one-year visual outcomes and safety.

    Science.gov (United States)

    Baily, Caroline; Kohnen, Thomas; O'Keefe, Michael

    2014-08-01

    To report the results of the Icolens corneal inlay 12 months after implantation. Department of Refractive Surgery, Mater Private Hospital, Dublin, Ireland. Prospective case series. The inlay was implanted in the nondominant eye of emmetropic patients through a femtosecond laser-created corneal pocket. The mean uncorrected near visual acuity (UNVA) in the surgical eye (n = 52) improved from N18/N24 preoperatively to N8 postoperatively (P = .000); all patients had a UNVA of N16 or better and 9 (17%), of N5 or better. The uncorrected distance visual acuity (UDVA) in the surgical eye increased from 0.05 logMAR ± 0.12 (SD) preoperatively to 0.22 ± 0.15 logMAR postoperatively (P = .000). There was a mean loss of 1.67 ± 1.77 lines of UDVA (P = .000). Binocularly, there was a mean gain of 0.48 ± 1.16 lines of UDVA postoperatively (P = .000), with 22 patients (42%) gaining more than 1 line. The mean loss of corrected distance visual acuity postoperatively was 1.78 ± 1.04 lines (P = .000). There was no significant change in corneal topography or endothelial cell count. On the satisfaction survey, 90% of patients reported being happy ("yes" or "rather yes") with the overall procedure in general. Eleven implants were explanted because of minimal improvement in UNVA. No significant adverse events were reported throughout the study. The new refractive-addition corneal inlay effectively corrected presbyopia in emmetropic presbyopic patients. No author has a financial or proprietary interest in any material or method mentioned. Copyright © 2014. Published by Elsevier Inc.

  17. 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.

  18. Correlations between corneal hysteresis, intraocular pressure, and corneal central pachymetry.

    Science.gov (United States)

    Touboul, David; Roberts, Cynthia; Kérautret, Julien; Garra, Caroline; Maurice-Tison, Sylvie; Saubusse, Elodie; Colin, Joseph

    2008-04-01

    To analyze the correlation between corneal hysteresis (CH) measured with the Ocular Response Analyzer (ORA, Reichert) and ultrasonic corneal central thickness (CCT US) and intraocular pressure measured with Goldmann applanation tonometry (IOP GA). Bordeaux 2 University, Ophthalmology Department, Bordeaux, France. This study comprised 498 eyes of 258 patients. Corneal hysteresis, corneal resistance factor (CRF), and IOP corneal-compensated (IOPcc) were provided by the ORA device; CCT US and IOP GA were also measured in each eye. The study population was divided into 5 groups: normal (n = 122), glaucoma (n = 159), keratoconus (n = 88), laser in situ keratomileusis (LASIK) (n = 78), and photorefractive keratectomy (n = 39). The Pearson correlation was used for statistical analysis. Corneal hysteresis was not strongly correlated with IOP or CCT US. The mean CH in the LASIK (8.87 mm Hg) and keratoconus (8.34 mm Hg) groups was lower than in the glaucoma (9.48 mm Hg) and normal (10.26 mm Hg) groups. The lower the CH, the lower its correlation with IOPcc and IOP GA. A CH higher than the CRF was significantly associated with the keratoconus and post-LASIK groups. Corneal hysteresis, a new corneal parameter, had a moderate dependence on IOP and CCT US. Weaker corneas could be screened with ORA parameters, and low CH could be considered a risk factor for underestimation of IOP. The CCT US should continue to be considered a useful parameter.

  19. [Corneal biomechanics].

    Science.gov (United States)

    Torres, R M; Merayo-Lloves, J; Jaramillo, M A; Galvis, V

    2005-04-01

    To review the corneal biomechanic concepts and to analyse, clarify and understand their relevance in refractive surgery. A literature review has been done using different databases. Corneal biomechanic concepts are not new and are applied implicitly in numerous surgical procedures. Their origin is related to tonometry studies, but they gained in popularity when they were linked to the treatment of keratoconus, a pathology in which the mechanical properties of the cornea are altered. Factors determining corneal stability were thus defined. Corneal biomechanics have also been used following refractive surgery to study post-operative keratectasia and to improve ablation patterns, which ignores the corneal response. The new ablation systems need to include the biomechanical factors, which motivate research conducted in physical-mathematical models and in corneal wound healing, improving our knowledge about the corneal biomechanical response. The corneal biomechanic concepts have gained in popularity with the advent of refractive surgery, although they did exist previously. Their relevance is linked to improvements in the ablation systems used in an attempt to obtain more accurate and reliable results.

  20. Corneal Laceration

    Medline Plus

    Full Text Available ... Answers How often and for how long should I use a hair dryer to treat my Fuchs’ dystrophy? May 06, 2017 I lost sight from a corneal scar as a child. Now that I’m older, will a corneal transplant help me? ...

  1. Corneal Laceration

    Medline Plus

    Full Text Available ... Tips & Prevention News Ask an Ophthalmologist Patient Stories Español Eye Health / Eye Health A-Z Corneal Laceration ... Laceration Treatment What Is Corneal Laceration? Leer en Español: ¿Qué Es una Laceración de la Córnea? Written ...

  2. Corneal Laceration

    Medline Plus

    Full Text Available ... Health Find an Ophthalmologist Academy Store Eye Health A-Z Symptoms Glasses & Contacts Tips & Prevention News Ask ... Ophthalmologist Patient Stories Español Eye Health / Eye Health A-Z Corneal Laceration Sections What Is Corneal Laceration? ...

  3. Femtosecond laser corneal refractive surgery for the correction of high myopic anisometropic amblyopia in juveniles

    Directory of Open Access Journals (Sweden)

    Jing Zhang

    2017-11-01

    Full Text Available AIM: To evaluate the effects of femtosecond laser-assisted in situ keratomileusis (FS-LASIK and small-incision lenticule extraction (SMILE to correct high myopic anisometropic amblyopia in juvenile patients. METHODS: From November 2013 to January 2015, 33 amblyopic patients with high myopic anisometropic amblyopia were studied. FS-LASIK (30 eyes or SMILE (3 eyes was performed in the amblyopic eyes. Visual acuity, refraction, contrast sensitivity, stereoacuity and complications were evaluated. Patients completed follow-up examinations at 3d, 1mo, 3mo and the last follow-up time (mean 8.17±3.23mo after surgery. RESULTS: The mean age at surgery was 9.04±3.04y (range 6-16y. The mean spherical equivalent in the amblyopic eyes was significantly decreased from -10.00±2.39 D preoperatively to -0.06±1.06 D at 1mo, -0.19±1.33 D at 3mo and -0.60±1.43 D at approximately 8mo postoperatively (P<0.05 for all. The mean myopic anisometropia was significantly decreased from -9.45±2.33 D preoperatively to +0.37±1.48 D at 1mo, -0.46±1.47 D at 3mo and -0.09±1.83 D at approximately 8mo (P<0.05 for all. The logarithm of the minimum angle of resolution (logMAR for uncorrected and corrected distance visual acuity (UDVA and CDVA, respectively of the amblyopic eye improved from 1.74±0.35 and 0.98±0.63 preoperatively to 0.45±0.31 and 0.41±0.33 at approximately 8mo after surgery, respectively. The logMAR CDVA at 3d, 1, 3 and 8mo postoperatively improved by means of 1.42, 2.22, 2.96, and 4.39 lines, and a gain of more than two lines accounted for 45%, 50%, 74% and 86% of all patients, respectively. The contrast sensitivity of both amblyopic eyes and dominant eyes at 0.5, 2, 8 cycles per degree was significantly improved postoperatively (P<0.05 for all. Of the 33 pediatric patients, no patients had near stereopsis preoperatively and seven patients (21.2% recovered near stereopsis (400″ to 60″ at approximately 8mo after surgery. No intraoperative or

  4. Human corneal epithelial subpopulations

    DEFF Research Database (Denmark)

    Søndergaard, Chris Bath

    2013-01-01

    subpopulations in human corneal epithelium using a combination of laser capture microdissection and RNA sequencing for global transcriptomic profiling. We compared dissociation cultures, using either expansion on γ-irradiated NIH/3T3 feeder cells in serum-rich medium or expansion directly on plastic in serum......-free EpiLife medium, using a range of physiologically relevant oxygen concentrations (2%, 5%, 10%, 15% and 20%). Using immunocytochemistry and advanced fluorescence microscopy, cells were characterized regarding growth, cell cycle distribution, colony-forming efficiency (CFE), phenotypes...... was not dependent on the system used for propagation (Bath et al. 2013a). Laser capture microdissection was used to isolate cellular subpopulations in situ from the spatially defined differentiation pathway in human corneal epithelium according to an optimized protocol for maintenance of expression profiles...

  5. Clinical use of in vivo confocal microscopy through focusing in corneal refractive surgery.

    Science.gov (United States)

    Ying, Li; Xiao, Zhang; Liuxueying, Zhong; Yumei, Jin

    2006-11-01

    To illustrate the use of in vivo confocal microscopy through focusing to observe normal cornea and corneal wound healing after excimer laser refractive surgery. A total of 197 eyes, including both unoperated eyes and eyes that had undergone LASIK, photorefractive keratectomy (PRK), or laser epithelial keratomileusis (LASEK), were examined using in vivo confocal microscopy through focusing. Images of the various corneal layers resolved by confocal microscopy through focusing were recorded and analyzed. Pachymetry of the cornea, epithelium, and stroma was also recorded for all eyes. The t test was used to evaluate the differences between unoperated eyes and postoperative eyes and the change in corneal pachymetry preoperatively to postoperatively with each type of surgery. A P value <.05 was considered statistically significant. Each layer of the cornea could be resolved in unoperated eyes and eyes that had undergone refractive surgery. Wound healing could be followed over time using confocal microscopy through focusing. In eyes that underwent PRK, at 1 month postoperatively, the entire cornea and stroma were thinner than preoperatively, whereas the epithelial layer was statistically significantly thicker (P<.05). Haze after PRK is seen as reflectivity of subepithelial anterior stroma. No clinically significant haze was observed in eyes that underwent LASEK or LASIK. The features of the eyes that underwent LASIK were the same as those of unoperated eyes. Confocal microscopy through focusing was useful in documenting cellular morphology in unoperated corneas and corneas that had undergone refractive surgery. Wound-healing characteristics of eyes that had undergone refractive surgery were also documented using confocal microscopy.

  6. Reasons not to select patients for corneal refractive surgery Razões para recusar candidatos à cirurgia refrativa corneana

    Directory of Open Access Journals (Sweden)

    André Luiz Parolin Ribeiro

    2002-08-01

    Full Text Available Purpose: To present how the section of Refractive Surgery of the Federal University of São Paulo assesses the candidates and the reasons to indicate for corneal refractive surgery. Methods: We examined 1626 patients. Anamnesis, complete ophthalmologic examination and corneal topography were performed in all patients. The patients spontaneously seeked evaluation at the Refractive Surgery Section by telephone without a previous screening. Reasons to refuse patients for refractive surgery were previously established by the Refractive Surgery Section. Results: Based on current technology and clinical experience, 265 patients (16.29% were refused for excimer laser corneal refractive surgery. Myopia of patients who had insufficient preoperative corneal pachymetry for the laser treatment was the main cause for refusal (51 patients. Cataract (45 patients, keratoconus (31 patients, amblyopia (21 patients, hyperopia > 5 diopters and mixed astigmatism (19 patients, presbyopia (unaware ness of the need for optical correction after the procedure; 16 patients, pupillary diameter > 5mm (9 patients, single eye (9 patients, progressive myopia (8 patients, postradial keratotomy (7 patients and low ametropia (7 patients were among the reasons for the refusal. Conclusion: Candidates for excimer laser corneal refractive surgery may present risk factors that should be known in order to avoid complications.Objetivo: O objetivo deste estudo é mostrar como o setor de Cirurgia Refrativa da Escola Paulista de Medicina da Universidade Federal de São Paulo avalia seus candidatos e quais as razões para não selecioná-los para cirurgia refrativa. Métodos: Foram examinados 1626 pacientes. Anamnese, avaliação oftalmológica completa e topografia corneana foram realizadas em todos os pacientes. Os pacientes procuraram avaliação no setor de Cirurgia Refrativa espontaneamente sem triagem prévia. Resultados: Não foram selecionados 265 pacientes (16,29% para cirurgia

  7. 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.

  8. Effects of laser peripheral iridotomy on corneal endothelial cell density and cell morphology in primary angle closure suspect subjects

    Directory of Open Access Journals (Sweden)

    Hossein Jamali

    2016-01-01

    Conclusion: In PACS eyes, we did not find a decline in corneal endothelial cell density or a change in cell morphological characteristics, including cell hexagonality and CV, in the central, nasal, and temporal regions of the cornea in any of our subjects over a one-year follow-up period.

  9. 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.

  10. The retinal nerve fibre layer thickness in glaucomatous hydrophthalmic eyes assessed by scanning laser polarimetry with variable corneal compensation in comparison with age-matched healthy children.

    Science.gov (United States)

    Hložánek, Martin; Ošmera, Jakub; Ležatková, Pavlína; Sedláčková, Petra; Filouš, Aleš

    2012-12-01

    To compare the thickness of the retinal nerve fibre layer (RNFL) in hydrophthalmic glaucomatous eyes in children with age-matched healthy controls using scanning laser polarimetry with variable corneal compensation (GDxVCC). Twenty hydrophthalmic eyes of 20 patients with the mean age of 10.64 ± 3.02 years being treated for congenital or infantile glaucoma were included in the analysis. Evaluation of RNFL thickness measured by GDxVCC in standard Temporal-Superior-Nasal-Inferior-Temporal (TSNIT) parameters was performed. The results were compared to TSNIT values of an age-matched control group of 120 healthy children published recently as referential values. The correlation between horizontal corneal diameter and RNFL thickness in hydrophthalmic eyes was also investigated. The mean ± SD values in TSNIT Average, Superior Average, Inferior Average and TSNIT SD in hydrophthalmic eyes were 52.3 ± 11.4, 59.7 ± 17.1, 62.0 ± 15.6 and 20.0 ± 7.8 μm, respectively. All these values were significantly lower compared to referential TSNIT parameters of age-matched healthy eyes (p = 0.021, p = 0.001, p = 0.003 and p = 0.018, respectively). A substantial number of hydrophthalmic eyes laid below the level of 5% probability of normality in respective TSNIT parameters: 30% of the eyes in TSNIT average, 50% of the eyes in superior average, 30% of the eyes in inferior average and 45% of the eyes in TSNIT SD. No significant correlation between enlarged corneal diameter and RNFL thickness was found. The mean values of all standard TSNIT parameters assessed using GDxVCC in hydrophthalmic glaucomatous eyes in children were significantly lower in comparison with referential values of healthy age-matched children. © 2011 The Authors. Acta Ophthalmologica © 2011 Acta Ophthalmologica Scandinavica Foundation.

  11. 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.

  12. Corneal Laceration

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    Full Text Available ... by something sharp flying into the eye. It can also be caused by something striking the eye ... If the corneal laceration is deep enough it can cause a full thickness laceration. This is when ...

  13. Corneal Laceration

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    Full Text Available ... itself. A corneal laceration is a very serious injury and requires immediate medical attention to avoid severe ... 27, 2015 Dark Spot in Vision After Blunt Trauma Dec 21, 2014 Pain a Year After Eyelid ...

  14. Corneal Laceration

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    Full Text Available ... the blood and may increase bleeding after you have finished protecting the eye, see a physician immediately ... Jun 30, 2017 People with Advanced Keratoconus May Have A Future Alternative to Full Corneal Transplantation Nov ...

  15. Corneal Laceration

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    Full Text Available ... People with Advanced Keratoconus May Have A Future Alternative to Full Corneal Transplantation Nov 29, 2016 Combating Eye Injuries from ... of Service For Advertisers For Media Ophthalmology Job Center © American Academy of Ophthalmology 2017 ...

  16. Corneal Laceration

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    Full Text Available ... inflammatory drugs. These drugs thin the blood and may increase bleeding after you have finished protecting the ... a hair dryer to treat my Fuchs’ dystrophy? May 06, 2017 I lost sight from a corneal ...

  17. Corneal Laceration

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    Full Text Available ... By: Devin A Harrison MD Sep. 01, 2017 The cornea is the clear front window of the eye . A corneal laceration is a cut on the cornea. It is usually caused by something sharp ...

  18. Corneal Laceration

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    Full Text Available ... itself. A corneal laceration is a very serious injury and requires immediate medical attention to avoid severe ... Ask an Ophthalmologist Answers Did my traumatic brain injury cause early cataracts? Jan 21, 2018 Did I ...

  19. Corneal Laceration

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    Full Text Available ... caused by something striking the eye with significant force, like a metallic hand tool. A corneal laceration ... and preserving your vision. Privacy Policy Related Top 5 Eye Health Stories of 2017 Dec 21, 2017 ...

  20. Corneal Laceration

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    Full Text Available ... itself. A corneal laceration is a very serious injury and requires immediate medical attention to avoid severe ... Dangerous for Your Eyes Sep 20, 2017 Eye Injuries from Laundry Packets On the Rise Jun 30, ...

  1. 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.

  2. Corneal collagens.

    Science.gov (United States)

    Robert, L; Legeais, J M; Robert, A M; Renard, G

    2001-05-01

    Cornea is a highly differentiated tissue rich in extracellular matrix (ECM) specifically distributed in space in order to insure its dual role--transparency and protection of inner eye-tissues. Corneal ECM is especially rich in collagens. Since the characterisation of a number of distinct collagen types it appeared that most of them are present in the cornea. Their synthesis follows a specific program of sequential expression of the different collagen types to be synthesised during the development and maturation of the cornea. The precise regulation of the diameter and orientation of fibers, and of the interfibrillar spaces is partially at least attributed to interactions between glycosaminoglycans and collagens. The 'program' of vectorial collagen synthesis and GAG-collagen interactions changes also with age and in several pathological conditions as corneal dystrophies and wound healing. The Maillard reaction, especially in diabetes, is one of these important factors involved in age-dependent modifications of corneal structure and function. Far from being inert, corneal collagens were shown to have relatively short half-lives. The biosynthesis of corneal collagens was studied also during wound healing. The refibrillation of wounded corneas does not follow the original 'program' of ECM-synthesis as shown by the comparative study of wound healing using biochemical and morphometric methods. This review recapitulates briefly previous and recent studies on corneal collagens in order to present to clinicians and scientists an overview of the state of the art of this important field at the intersection of eye research and matrix biology.

  3. 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.

  4. Current status of accelerated corneal cross-linking

    Directory of Open Access Journals (Sweden)

    Michael Mrochen

    2013-01-01

    Full Text Available Corneal cross-linking with riboflavin is a technique to stabilize or reduce corneal ectasia, in diseases such as keratoconus and post-laser-assisted in situ keratomileusis (LASIK ectasia. There is an interest by patient as well as clinicians to reduce the overall treatment time. Especially, the introduction of corneal cross-linking in combination with corneal laser surgery demands a shorter treatment time to assure a sufficient patient flow. The principles and techniques of accelerated corneal cross-linking is discussed.

  5. 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.

  6. Corneal Transplantation

    DEFF Research Database (Denmark)

    Hjortdal, Jesper Østergaard

    Corneal transplantation has been performed for more than 100 years. Until 15 years ago the state-of-the art type of transplantation was penetrating keratoplasty, but since the start of this millennium, newly designed surgical techniques have developed considerably. Today, the vast majority...... with less risk of rejection episodes. Besides covering updated chapters on penetrating keratoplasty, and anterior and posterior lamellar procedures, this textbook also gives a thorough overview of the history of corneal transplantation and a detailed presentation of the microstructural components....... Economic considerations on cost and benefi t of medical treatment and surgical procedures are today an integrated part of the health system in many countries, and a chapter covers these aspects of corneal transplantation. This textbook is aimed at presenting an updated review of the new techniques...

  7. [Intraocular pressure, ocular blood flow, and corneal biomechanics changes after LASIK surgery for myopia].

    Science.gov (United States)

    Avetisov, S E; Mamikonyan, V R; Shmeleva-Demir, O A; Karamyan, A A; Bubnova, I A; Kazaryan, E E; Galoyan, N S; Karapetyan, A T

    2016-01-01

    to study changes in intraocular pressure (IOP), volumetric ocular blood flow (OBF) rate, and biomechanical properties of the cornea after excimer laser ablation in patients with myopia of different degrees. A total of 16 patients (32 eyes) with myopia ranging from 2.75 to 9.0 D were examined before and after LASIK. Ocular Blood Flow Analyzer (OBFA) was used to measure IOP and OBF as well as pulse amplitude and volume. Ocular Response Analyzer (ORA) was also employed to provide the following data: Goldmann-equivalent IOP, corneal compensated IOP, corneal hysteresis, and corneal resistance factor. The eyes were then divided into two groups: group 1 - 15 eyes with less than 70-µm deep ablation of the cornea and group 2 - 17 eyes with more than 70-µm deep ablation. Group 1 demonstrated a statistically reliable decrease in IOP values provided by either method and biomechanical parameters of the cornea (p0.05). In group 2, all the parameters changed reliably, except for the pulse volume (p>0.05). In particular, a decrease was recorded for IOP (with no dependence to the method of measurement; pcorneal hysteresis (pcorneal resistance factor (p<0.001); an increase - for OBF (p<0.05). One should allow for possible mismeasurement of IOP and OBF as well as biomechanical parameters of the cornea in post-LASIK patients, keeping in mind that the extent of error depends on the depth of ablation. Shallow ablation (no more than 70-µm deep) has no statistically significant effect on OBF readings, while IOP seems to decrease considerably. In deep ablation (more than 70-µm deep), both parameters are reliably lower than at baseline.

  8. Technology needs for corneal transplant surgery

    Science.gov (United States)

    Vaddavalli, Pravin K.; Yoo, Sonia H.

    2011-03-01

    Corneal transplant surgery has undergone numerous modifications over the years with improvements in technique, instrumentation and eye banking. The main goals of corneal transplantation are achieving excellent optical clarity with long-term graft survival. Penetrating, anterior and posterior lamellar surgery along with femtosecond laser technology have partially met these goals, but outcomes are often unpredictable and surgeon dependent. Technology to predictably separate stroma from Descemet's membrane, techniques to minimize endothelial cell loss, improvements in imaging technology and emerging techniques like laser welding that might replace suturing, eventually making corneal transplantation a refractively predictable procedure are on the wish list of the cornea surgeon.

  9. Paradigm shifts in corneal transplantation.

    Science.gov (United States)

    Tan, Donald T H; Anshu, Arundhati; Mehta, Jodhbir S

    2009-04-01

    Conventional corneal transplantation, in the form of penetrating keratoplasty (PK), involves full-thickness replacement of the cornea, and is a highly successful procedure. However, the cornea is anatomically a multi-layered structure. Pathology may only affect individual layers of the cornea, hence selective lamellar surgical replacement of only the diseased corneal layers whilst retaining unaffected layers represents a new paradigm shift in the field. Recent advancements in surgical techniques and instrumentation have resulted in several forms of manual, microkeratome and femto-second laser-assisted lamellar transplantation procedures. Anterior lamellar keratoplasty (ALK) aims at replacing only diseased or scarred corneal stroma, whilst retaining the unaffected corneal endothelial layer, thus obviating the risk of endothelial allograft rejection. Posterior lamellar keratoplasty/endothelial keratoplasty (PLK/EK) involves the replacement of the dysfunctional endothelial cell layer only. Whilst significant technical and surgical challenges are involved in performing lamellar micro-dissection of a tissue which is only 0.5 mm thick, the benefits of a more controlled surgical procedure and improved graft survival rates have resulted in a shift away from conventional PK. This review details the current advances in emerging lamellar corneal surgical procedures and highlights the main advantages and disadvantages of these new lamellar corneal procedures.

  10. Corneal Intelligence

    African Journals Online (AJOL)

    Murdoch3

    the damping effect of the tissue to an applied force) or corneal compliance being the major risk factor. Figure 1. The percentage of participants in the observation group who developed primary open-angle glaucoma (median follow-up, 72 months) ...

  11. Corneal ulcers

    African Journals Online (AJOL)

    visual acuity chart. • fluorescein strips. • topical anaesthetic eye drops. • direct ophthalmoscope. Examination. Assessing vision with a Snellen visual acuity chart gives a clue as to the extent of the problem (e.g. a corneal abrasion with good vision is unlikely to require specialist intervention). Each eye should be tested ...

  12. Corneal Intelligence

    African Journals Online (AJOL)

    Murdoch3

    Corneal Intelligence. Ian Murdoch. Institute of Ophthalmology, Bath Street, London. In 2002, the ocular hypertension treatment study (OHTS) published their results. This study had taken 1636 ocular hypertensives. 1, 2. (IOP 24-32mmHg) and randomized them to receive therapy or no therapy. The primary outcome of the ...

  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. Corneal thickness changes after corneal collagen crosslinking for keratoconus and corneal ectasia: one-year results.

    Science.gov (United States)

    Greenstein, Steven A; Shah, Vinnie P; Fry, Kristen L; Hersh, Peter S

    2011-04-01

    To determine the changes in corneal thickness over time after corneal collagen crosslinking (CXL) for keratoconus and corneal ectasia. Cornea and refractive surgery subspecialty practice. Prospective randomized controlled clinical trial. Corneal thickness at the apex, thinnest point, and pupil center were measured using Scheimpflug imaging (Pentacam) at baseline and 1, 3, 6, and 12 months after CXL. The treatment group was compared with both a sham-procedure control group and a fellow-eye control group. Associations with clinical outcomes (uncorrected and corrected distance visual acuities and maximum keratometry) were analyzed. The study comprised 82 eyes, 54 with keratoconus and 28 with ectasia after laser in situ keratomileusis. The mean preoperative thinnest pachymetry was 440.7 μm ± 52.9 (SD). After CXL, the cornea thinned at 1 month (mean change -23.8 ± 28.7 μm; Pdegree of corneal thinning at 3 months and clinical outcomes after CXL. After CXL, the cornea thins and then recovers toward baseline thickness. The cause and implications of corneal thickness changes after CXL remain to be elucidated. No author has a financial or proprietary interest in any material or method mentioned. Additional disclosure is found in the footnotes. Copyright © 2011 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  16. Effects of new biomimetic regenerating agents on corneal wound healing in an experimental model of post-surgical corneal ulcers.

    Science.gov (United States)

    Alcalde, I; Íñigo-Portugués, A; Carreño, N; Riestra, A C; Merayo-Lloves, J M

    2015-10-01

    The purpose of this study is to assess the effectiveness of the topical application of cacicol regenerating agent (RGTA) in an experimental model of corneal ulcer after photorefractive keratectomy (PRK) in mice. Mice were subjected to PRK surgery with a 2.0mm ablation zone on the central cornea and 45mm of depth on a VISX Star S2 excimer laser. Corneas were treated topically with cacicol drops 1hour and 48hours after injury. Control groups received balanced salt solution (BSS) in the same dosage. Clinical and histopathological events were evaluated at 1, 2, 3 and 7 days after surgery. Sections obtained through the central region of the corneas were used to analyze the histopathological events of injured and healed corneas. αSMA (myofibroblast transformation), E cadherin (assembly of epithelial cells) and neuronal class III β-tubulin (innervation) were performed. Corneas treated topically with cacicol for 7 days showed a greater degree of transparency compared to controls. cacicol treated corneas showed improved epithelial cytoarchitecture. Analysis of αSMA profiles in the stroma showed that cacicol reduced or delayed the presence of myofibroblasts in the stroma compared to BSS (P<0.001). Finally, a putative neuroregenerative effect of cacicol was found in corneas subjected to an experimental PRK lesion. In some cases some interindividual variability could be observed due to the design of the experimental model. This is a limitation to consider, despite the statistical significance of the data. In a model of laser induced surgical lesions in the cornea, topical application of an RGTA (i.e. cacicol) could be involved in avoiding myofibroblast scarring formation and promoting nerve regeneration. Copyright © 2014 Sociedad Española de Oftalmología. Published by Elsevier España, S.L.U. All rights reserved.

  17. 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

  18. High interocular corneal symmetry in average simulated keratometry, central corneal thickness, and posterior elevation.

    Science.gov (United States)

    Myrowitz, Elliott H; Kouzis, Anthony C; O'Brien, Terrence P

    2005-05-01

    The purpose of this study was to assess interocular corneal symmetry in average simulated keratometry, corneal thickness, and posterior corneal elevation. This retrospective analysis included data from scanning slit topography (Orbscan II; Bausch and Lomb, Rochester, NY) on 242 eyes from 121 consecutive patients undergoing standard evaluation for consideration of elective laser vision correction. The symmetry between the right and left eye in average simulated keratometry, minimum central corneal thickness, and posterior corneal elevation was assessed by comparative data analysis. Simulated keratometry ranged from 39.9 to 48.6 D. The interocular difference in average simulated keratometry was 0.47 D (standard deviation [SD] 0.43). The interocular Pearson correlation coefficient for average simulated keratometry was 0.90 (p central corneal thickness was 0.95 (p symmetry in all these parameters was very high in this group of consecutive patients. Asymmetry of these interocular parameters may warrant repeat clinical testing for accuracy and may predict corneal abnormalities. Normative data on posterior cornea elevation is presented. This study points out potentially clinically important high interocular corneal symmetry data in simulated keratometry, corneal thickness, and posterior corneal elevation.

  19. 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.

  20. Proteomic Analyses of the Acute Tissue Response for Explant Rabbit Corneas and Engineered Corneal Tissue Models Following In Vitro Exposure to 1540 nm Laser Light

    National Research Council Canada - National Science Library

    Eurell, T. E; Johnson, T. E; Roach, W. P

    2005-01-01

    Two-dimensional electrophoresis and histomorphometry were used to determine if equivalent protein changes occurred within native rabbit corneas and engineered corneal tissue models following in vitro...

  1. 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.

  2. Corneal Laceration

    Medline Plus

    Full Text Available ... Uveitis Focus On Pediatric Ophthalmology Education Center Oculofacial Plastic Surgery Center Laser Surgery Education Center Redmond Ethics Center ... Uveitis Focus On Pediatric Ophthalmology Education Center Oculofacial Plastic Surgery Center Laser Surgery Education Center Redmond Ethics Center ...

  3. Corneal Laceration

    Medline Plus

    Full Text Available ... Plastic Surgery Center Laser Surgery Education Center Redmond Ethics Center Global Ophthalmology Guide Academy Publications EyeNet Ophthalmology ... Plastic Surgery Center Laser Surgery Education Center Redmond Ethics Center Global Ophthalmology Guide Find an Ophthalmologist Advanced ...

  4. Corneal Laceration

    Medline Plus

    Full Text Available ... Uveitis Focus On Pediatric Ophthalmology Education Center Oculofacial Plastic Surgery Center Laser Surgery Education Center Redmond Ethics Center ... Glaucoma Education Center Pediatric Ophthalmology Education Center Oculofacial Plastic ... Center Laser Surgery Education Center Redmond Ethics Center ...

  5. Corneal Laceration

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    Full Text Available ... Uveitis Focus On Pediatric Ophthalmology Education Center Oculofacial Plastic Surgery Center Laser Surgery Education Center Redmond Ethics ... Glaucoma Education Center Pediatric Ophthalmology Education Center Oculofacial Plastic Surgery Center Laser Surgery Education Center Redmond Ethics ...

  6. Repeatability and Reproducibility of Retinal Nerve Fiber Layer Parameters Measured by Scanning Laser Polarimetry with Enhanced Corneal Compensation in Normal and Glaucomatous Eyes.

    Science.gov (United States)

    Ara, Mirian; Ferreras, Antonio; Pajarin, Ana B; Calvo, Pilar; Figus, Michele; Frezzotti, Paolo

    2015-01-01

    To assess the intrasession repeatability and intersession reproducibility of peripapillary retinal nerve fiber layer (RNFL) thickness parameters measured by scanning laser polarimetry (SLP) with enhanced corneal compensation (ECC) in healthy and glaucomatous eyes. One randomly selected eye of 82 healthy individuals and 60 glaucoma subjects was evaluated. Three scans were acquired during the first visit to evaluate intravisit repeatability. A different operator obtained two additional scans within 2 months after the first session to determine intervisit reproducibility. The intraclass correlation coefficient (ICC), coefficient of variation (COV), and test-retest variability (TRT) were calculated for all SLP parameters in both groups. ICCs ranged from 0.920 to 0.982 for intravisit measurements and from 0.910 to 0.978 for intervisit measurements. The temporal-superior-nasal-inferior-temporal (TSNIT) average was the highest (0.967 and 0.946) in normal eyes, while nerve fiber indicator (NFI; 0.982) and inferior average (0.978) yielded the best ICC in glaucomatous eyes for intravisit and intervisit measurements, respectively. All COVs were under 10% in both groups, except NFI. TSNIT average had the lowest COV (2.43%) in either type of measurement. Intervisit TRT ranged from 6.48 to 12.84. The reproducibility of peripapillary RNFL measurements obtained with SLP-ECC was excellent, indicating that SLP-ECC is sufficiently accurate for monitoring glaucoma progression.

  7. Corneal Backscatter Analysis by In Vivo Confocal Microscopy: Fellow Eye Comparison of Small Incision Lenticule Extraction and Femtosecond Laser-Assisted LASIK

    Directory of Open Access Journals (Sweden)

    Alper Agca

    2014-01-01

    Full Text Available Purpose. To evaluate and compare corneal backscatter from anterior stroma between small incision lenticule extraction (SMILE and femtosecond laser-assisted LASIK (femto-LASIK. Methods. A cohort of 60 eyes of 30 patients was randomized to receive SMILE in one eye and femto-LASIK in the fellow eye. In vivo confocal microscopy was performed at 1 week and 1, 3, and 6 months after surgery. The main outcome measurements were maximum backscattered intensity and the depth from which it was measured, the backscattered light intensity 30 μm below Bowman’s membrane at the flap interface and 150 μm below the superficial epithelium, and the number of refractive particles at the flap interface. Results. The mean backscattered light intensity (LI at all measured depths and the maximum backscattered LI were higher in the SMILE group than the femto-LASIK group at all postoperative visits. LI differences at 1 week and 1- and 3-month visits were statistically significant (P<0,05. LI differences at 6 months were not statistically significant. There was no difference in the number of refractive particles at the flap interface between the groups at any visit. Conclusions. SMILE results in increased backscattered LI in the anterior stroma when compared with femto-LASIK were evaluated.

  8. A Large-Scale Computational Analysis of Corneal Structural Response and Ectasia Risk in Myopic Laser Refractive Surgery.

    Science.gov (United States)

    Dupps, William Joseph; Seven, Ibrahim

    2016-08-01

    To investigate biomechanical strain as a structural susceptibility metric for corneal ectasia in a large-scale computational trial. A finite element modeling study was performed using retrospective Scheimpflug tomography data from 40 eyes of 40 patients. LASIK and PRK were simulated with varied myopic ablation profiles and flap thickness parameters across eyes from LASIK candidates, patients disqualified for LASIK, subjects with atypical topography, and keratoconus subjects in 280 simulations. Finite element analysis output was then interrogated to extract several risk and outcome variables. We tested the hypothesis that strain is greater in known at-risk eyes than in normal eyes, evaluated the ability of a candidate strain variable to differentiate eyes that were empirically disqualified as LASIK candidates, and compared the performance of common risk variables as predictors of this novel susceptibility marker across multiple virtual subjects and surgeries. A candidate susceptibility metric that expressed mean strains across the anterior residual stromal bed was significantly higher in eyes with confirmed ectatic predisposition in preoperative and all postoperative cases (P≤.003). The strain metric was effective at differentiating normal and at-risk eyes (area under receiver operating characteristic curve ≥ 0.83, P≤.002), was highly correlated to thickness-based risk metrics (as high as R(2) = 95%, Prefractive response to surgery (R(2) = 57%, Prefractive surgery. Mechanical strain is an effective marker of known ectasia risk and correlates to predicted refractive error after myopic photoablative surgery.

  9. Corneal plaque containing levofloxacin in a dog.

    Science.gov (United States)

    Park, Young-Woo; Kang, Byung-Jae; Lim, Jae Hyun; Ahn, Jung-Mo; Lim, Hyun Sook

    2015-11-01

    A 13-year-old castrated male Yorkshire terrier developed a corneal ulcer 2 weeks after intracapsular lens extraction (ICLE) in the right eye. The corneal ulcer was treated with levofloxacin eye drops. A plaque with a white luster developed in the central cornea 2 weeks after treatment with levofloxacin eye drops. The corneal plaque was surgically removed under inhalant anesthesia. The corneal plaque displayed antimicrobial activity against Escherichia coli. Furthermore, levofloxacin content in the plaque was confirmed by matrix-assisted laser desorption/ionization time-of-flight/time-of-flight (MALDI-TOF/TOF) mass spectrometry (MS). The corneal ulcer completely resolved 2 weeks after the surgical removal of the corneal lesion and replacement of levofloxacin eye drops with tobramycin eye drops. Although the topical use of levofloxacin is unlikely to lead to corneal chemical deposits due to the high water solubility of the drug compared to other topical fluoroquinolones, this patient developed corneal plaque of the antibiotic drop. © 2015 American College of Veterinary Ophthalmologists.

  10. Corneal collagen crosslinking for keratoconus. A review

    OpenAIRE

    M. M. Bikbov; V. K. Surkova

    2014-01-01

    Photochemical crosslinking is widely applied in ophthalmology. Its biochemical effect is due to the release of singlet oxygen that promotes anaerobic photochemical reaction. Keratoconus is one of the most common corneal ectasia affecting 1 in 250 to 250 000 persons. Currently, the rate of iatrogenic ectasia following eximer laser refractive surgery increases due to biomechanical weakening of the cornea. Morphologically and biochemically, ectasia is characterized by corneal layers thinning, co...

  11. 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.

  12. Correlation of both corneal surfaces in corneal ectasia after myopic LASIK.

    Science.gov (United States)

    Peinado, Teresa Fernández; Piñero, David P; López, Ignacio Alcaraz; Alio, Jorge L

    2011-04-01

    We report a case of corneal ectasia in a 25-year-old man after myopic laser in situ keratomileusis in which a complete characterization of the corneal structure was performed by means of a Scheimpflug photography-based system. The patient presented in the ectatic eye with a subjective refraction of +0.50 to 6.00 × 100°, which with correction gave a visual acuity of 20/25. With the topographic analysis, corneal shapes from both corneal surfaces at the four different quadrants were found to be complementary, maintaining the meniscus-shaped profile of the cornea. This correlation between the anterior and posterior corneal surfaces was also confirmed with an optical tomography evaluation. Corneal biomechanics was also evaluated by means of the Ocular Response Analyzer (Reichert), which confirmed the biomechanical alteration. In summary, biomechanical changes leading to corneal ectasia in this case affected the global corneal structure, inducing alterations in the shape of both anterior and posterior corneal surfaces.

  13. Corneal hysteresis, resistance factor, topography, and pachymetry after corneal lamellar flap.

    Science.gov (United States)

    Gatinel, Damien; Chaabouni, Slim; Adam, Pierre-Alexandre; Munck, Jacques; Puech, Michel; Hoang-Xuan, Thanh

    2007-01-01

    To measure prospectively the early changes in corneal hysteresis, topography, and pachymetry after the creation of a stromal flap cut without laser photoablation. A 37-year-old man was referred for a bioptic procedure to correct for compound myopic astigmatism in the left eye. A 159-microm-thick 8x8.5-mm superior hinged flap was created with a mechanical microkeratome in the left cornea. Changes in the corneal hysteresis, corneal resistance factor, Goldmann correlated intraocular pressure (lOP), corneal compensated IOP, anterior and posterior topography, and optical and ultrasound pachymetry were monitored prospectively before and at 1 hour, 1 day, 5 days, and 25 days after flap creation. The right eye served as a control. In the left eye, corneal hysteresis and corneal resistance factor decreased immediately after the flap cut and remained lower than preoperatively at 1 hour, 1 day, 5 days, and 25 days. Corneal compensated IOP varied significantly less than Goldmann correlated IOP in both eyes. Central flattening of the horizontal meridians was observed on the difference topography maps. The values of the left eye posterior best fit sphere increased after the flap cut. Increased central corneal thickness occurred immediately after the flap cut and decreased over time without returning to its preoperative value. The creation of a stromal flap can modify the biomechanical properties of the cornea, including a reduction in corneal hysteresis. The topographic changes were consistent with previously reported cases of flap cut in normal corneas.

  14. Repair of corneal ulcer or perforation using the corneal stromal lenticule

    Directory of Open Access Journals (Sweden)

    Xiao-Feng Hao

    2018-01-01

    Full Text Available AIM: To describe the outcomes of corneal stromal lenticules in repairing of corneal ulcer and/or perforation. METHODS: This was a retrospective chart review of 6 eyes of 6 patients from January to June 2017,who underwent corneal ulcer repair with the corneal, stromal lenticules harvested from femtosecond laser refractive surgery and kept in pure glycerin for use. Three cases of infectious corneal ulcers were bacterial, fungal, and infection with foreign bodies in corneal deep layer, one each. The other 3 were corneal ulcer perforation. Making sure no air bubble between donor graft and Descemet membrane. The mean follow-up time was 3.71±1.56mo(range 1-6mo. RESULTS: All eyes were successfully treated under control of infection without intra-operative complications, and early postoperative evaluation showed a clear graft in all cases. The last follow-up visit showed the mean best corrected visual acuity(VAsignificantly improved after surgery. There was significant difference from 0.48±0.12 to 1.50±0.08(PCONCLUSION: The preliminary results suggest that the use of corneal stromal lenticules may be a safe and effective surgical alternative for corneal ulcer, even though the long-term outcome of the graft needs to be further observed.

  15. Corneal Laceration

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  16. Corneal Transplantation in Children

    OpenAIRE

    Gabrić, N.; Dekaris, I.; Vojniković, B.; Karaman, Ž.; Mravičić, I.; Katušić, J.

    2001-01-01

    The main purpose of the study was to describe the surgical success rate and visual results of penetrating keratoplasty in children. This retrospective study included children that underwent corneal transplantation at the Department of Ophthalmology, General Hospital »Sveti Duh«, in the period 1994–1999. Patients’ age ranged from 6 to 16 years. Twenty-five corneal transplants were performed in 24 eyes. Corneal pathologies were corneal leucoma, congenital dystrophy, corneal combu...

  17. Influence of corneal astigmatism, corneal curvature and meridional differences on corneal hysteresis and corneal resistance factor.

    Science.gov (United States)

    Wong, Yin-zhi; Lam, Andrew K C

    2011-09-01

    This study investigated the influence of corneal astigmatism, corneal curvature and meridional differences on corneal hysteresis (CH) and the corneal resistance factor (CRF) in a group of normal Chinese persons. Ninety-five participants were recruited and data from the eye with higher corneal astigmatism were analysed. The anterior corneal curvature was measured by corneal topography. The Goldmann-correlated intraocular pressure (IOPg), corneal-compensated intraocular pressure (IOPcc), CH and CRF at different meridians (default horizontal position, 10°, 20° and 30° along the superotemporal and inferonasal meridians) were obtained from an ocular response analyser. The corneal powers at these specific meridians also were calculated. At the default position, the IOPg and CRF had weak correlations with corneal astigmatism, while the IOPcc and CH were not significantly correlated with corneal astigmatism. Both the IOPg and IOPcc were measured significantly higher at the default position. The CH and CRF were lower at the default position but the difference in the CRF from obliquity could not reach statistical significance. The CH was not significantly correlated with the corneal power at all meridians. The CRF correlated with the corneal power only at 30° superotemporal. Corneal astigmatism and head tilt did not have much effect on the measurement of CH and the CRF, both of which were lowest along the horizontal meridian. Clinically, the difference was small. The influence of corneal power on CH and the CRF was minimal. © 2011 The Authors. Clinical and Experimental Optometry © 2011 Optometrists Association Australia.

  18. Comparison of central corneal thickness measured by anterior segment optical coherence tomography, pentacam and ultrasonic pachymetry

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    Wei Zhao

    2013-12-01

    Full Text Available AIM: To investigate and analyze the differences in central corneal thickness(CCTmeasurement by anterior segment optical coherence tomography(AS-OCT, pentacam rotating Scheimpflug camera and ultrasonic pachymetry(USP. METHODS: The retrospective study measured CCT of 43 patients(86 eyesperformed excimer laser myopia corrective surgery by the same examiner using RTVue AS-OCT with an anterior segment adaptor, pentacam rotating Scheimpflug camera, and PACSCAN300P USP. Data of three groups were compared and statistically analyzed by pair t test.RESULTS: The mean CCT(±SDmeasured by AS-OCT,pentacam and USP were 535±52, 550±52, 550±51μm, respectively. Paired-sample t test showed that the results of AS-OCT, pentacam and USP were statistically different. There were no statistically significant differences in the mean CCT between the pentacam and USP group. Significant correlations of measurement result were found between pentacam and USP(r=0.998, Pr=0.993, Pr=0.991, PCONCLUSION:RTVue AS-OCT significantly under estimates the CCT, while the measurement results by pentacam are similar to those by USP which is regarded as the golden standard.

  19. Effects of corneal irregular astigmatism on visual acuity after conventional and femtosecond laser-assisted Descemet's stripping automated endothelial keratoplasty.

    Science.gov (United States)

    Tomida, Daisuke; Yamaguchi, Takefumi; Ogawa, Akiko; Hirayama, Yumiko; Shimazaki-Den, Seika; Satake, Yoshiyuki; Shimazaki, Jun

    2015-07-01

    To compare short-term outcomes of Descemet's stripping automated endothelial keratoplasty (DSAEK) using a graft prepared with either a femtosecond laser or a microkeratome. Thirty-eight patients underwent DSAEK with grafts prepared with either a femtosecond laser (f-DSAEK; 21 eyes) or a microkeratome (m-DSAEK; 17 eyes). Visual acuity, endothelial cell density, regular astigmatism and irregular astigmatism were compared between the two groups preoperatively and at 1, 3, and 6 months post-operatively. Fourier analysis was conducted to calculate astigmatism of the anterior and posterior surfaces, and total cornea, using anterior segment optical coherence tomography (AS-OCT). Visual acuity (logMAR) improved from 1.20 ± 0.60 to 0.43 ± 0.25 after m-DSAEK (P astigmatism of the total cornea and the posterior surface was significantly lar