Excimer Laser System Research Articles

Photorefractive keratectomy for myopia and myopic astigmatism correction using the WaveLight Allegretto Wave Eye-Q excimer laser system

To analyze photorefractive keratectomy (PRK) outcomes in myopia and myopic astigmatism correction using the WaveLight Allegretto Wave Eye-Q(®) excimer laser system (WaveLight Laser Technologie AG, Erlangen, Germany). 222 eyes of 151 patients underwent PRK (mean age 33.5 ± 6.8 years). Pre-operative best spectacle-corrected visual acuity (BSCVA) ranged from 0.4 to -0.1 logMAR (mean -0.03 ± 0.06). Mean spherical equivalent (SE) was -3.29 ± 1.20 D. Efficacy, predictability and safety were evaluated. Minimum follow-up was 3 months. Accountability at 3 and 6 months was 100 and 54 %, respectively (median follow-up 5 months, mean 5.2 ± 2.6 months). At 3 months, mean uncorrected visual acuity (UCVA) was -0.02 ± 0.07 logMAR, BSCVA -0.03 ± 0.05 logMAR, efficacy index 0.98 and safety index 1.02. UCVA was ≥20/16 in 40.1 %, ≥20/20 in 86.5 % and ≥20/25 in 98.2 %. Mean SE was -0.02 ± 0.20 D. Residual refractive error was ± 0.13 D in 81.5 %, ± 0.25 D in 88.7 % and ± 0.50 D in 97.7 %. At 6 months, outcomes were similar: mean UCVA was -0.02 ± 0.07 logMAR, BSCVA -0.03 ± 0.06 logMAR, efficacy index 1.00 and safety index 1.03. UCVA was ≥20/16 in 43.7 %, ≥20/20 in 86.6 % and ≥20/25 in 96.6 %. Mean SE was -0.02 ± 0.17 D. Residual refractive error was ± 0.13 D in 86.6 %, ± 0.25 D in 93.3 % and ± 0.50 D in 98.3 %. Refractive stability was achieved at 3 months. No patient lost more than one line of BSCVA. There were no retreatments. The WaveLight Allegretto Wave Eye-Q is effective, predictable and safe in low-to-moderate myopia and myopic astigmatism PRK correction.

Laser direct patterning of a reduced-graphene oxide transparent circuit on a graphene oxide thin film

In this study, reduced-graphene oxide (GO) circuits were directly patterned on glass using an industrially available excimer laser system. A threshold of laser energy density was observed, which provided a clear differentiation on whether the GO was reduced. A sharp drop of resistance by a factor of 104 was measured as the laser energy density increased from 65 to 75 mJ/cm2. The highest conductivity measured was ∼1.33 × 104 S/m, which is among the best reported in the literature for any laser reduction method. Raman analysis of the excimer laser-reduced GO film revealed the formation of a prominent 2D peak at 2700 cm−1. The relative signal strength between the Raman D and G peaks suggests that the amount of structural disorder in the reduced GO is insignificant. The reduced GO displays a transmittance greater than 80% across the entire range from 450 to 800 nm. The outstanding electrical, optical, and morphological properties have enabled graphene to display promising applications, and this nano-processing method makes graphene even more attractive when used as a transparent electrode for touch screens and in many more applications.

Beyond the balloon: excimer coronary laser atherectomy used alone or in combination with rotational atherectomy in the treatment of chronic total occlusions, non-crossable and non-expansible coronary lesions

To establish success and complication rates of excimer laser coronary atherectomy (ELCA) in a contemporary series of patients with balloon failure during percutaneous coronary intervention (PCI) of both chronic total occlusions (CTO) and lesions with distal TIMI 3 flow. We identified 58 cases of balloon failure treated with ELCA±rotational atherectomy (RA) over four years, representing 0.84% of all PCI performed in our centre during this period. Balloon failures were classified according to: (i) mechanism of balloon failure; and (ii) whether this occurred in the context of treating a CTO. ELCA was performed following balloon failure using the CVX-300 Excimer Laser System and a 0.9 mm catheter with saline flush. For the entire cohort, procedure success was achieved in 91% (with ELCA successful: alone in 76.1%, after RA failure in 6.8% and in combination with RA for 8.6%). Only in one case did RA succeed where ELCA had failed. There were four procedure-related complications, including transient no-reflow, side branch occlusion and two coronary perforations, of which one was directly attributable to ELCA and led to subsequent mortality. ELCA provides safe and effective adjunctive therapy in contemporary PCI to treat lesions associated with balloon failure due to an inability either to cross the lesion or to expand a balloon sufficiently to permit stenting. ELCA was successful in the majority of these selected cases when used independently with further effectiveness achieved when combined with RA or after RA failure.

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

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

Advanced techniques for chronic lead extraction: heading from the laser towards the evolution system

The evolution mechanical dilator sheath has been reported to be an effective tool for chronic lead extraction (LE). We examined safety and efficacy of evolution system as compared with laser system. From 2005 to 2009, all extractions requiring the use of a powered sheath were performed using the excimer laser system (n = 73). Since 2009, laser system was no longer available and the evolution system was introduced as the first-line method for powered extraction (n = 48). All procedures were performed by a single first operator. Success and complications were defined according to the current guidelines. Patients of the evolution group compared with those of the laser group had a greater number of extracted leads per patient (2.77 vs. 2.4, P = 0.049) and a longer implant duration (101.1 vs. 62.4 months, P = 0.001). Additional use of snare was required in 27.1% of the evolution group and 8.2% of the laser group (P = 0.005). Complete procedural success was achieved in 91.7% of the evolution group and 97.3% of the laser group (P = 0.16). There was also no difference between evolution and laser groups in clinical success (97.9 vs. 98.6%, P = 0.76), as well as regarding major (4.2 vs. 2.7%, P = 0.66) or minor complications (4.2 vs. 5.5%, P = 0.76). Use of the recently introduced evolution system for LE exhibit acceptably high levels of safety, as well as of procedural and clinical success, although additional use of snare was required more frequently in the evolution compared with the laser group.

Three different aspheric treatment algorithms of laser-assisted sub-epithelial keratectomy in patients with high myopia

To compare visual outcomes and quality in high myopia patients treated using one of three aspheric treatment algorithms based on the NIDEK Advanced Vision Excimer Laser System. Sixty eyes of 60 high myopia patients (>-6 diopter) underwent topography-guided (CATz) (20 eyes), wavefront-guided (OPDCAT) (20 eyes), or topography and wavefront-guided (OPA) (20 eyes) laser-assisted sub-epithelial keratectomy. Visual acuity, manifest refraction spherical equivalent (MRSE), ocular and corneal higher order aberrations, corneal asphericity, point spread function (Strehl ratio) and modulation transfer function (MTF) were compared preoperatively and 1, 3 and 6months postoperatively. Six months after surgery, logMAR uncorrected visual acuity was 0.02±0.09 in the CATz group, 0.02±0.07 in the OPDCAT group and 0.02±0.08 in the OPA group, and there were no statistically significant differences (P=0.5355). No statistical differences were found among the three groups in MRSE (P=0.3541). Induced spherical aberrations and the change of corneal asphericity were less in the OPA group than in the others (P<0.0001). The MTF was slightly better in the OPA group than in the others. The Strehl ratio showed no statistically significant differences among the three groups. All three aspheric treatment algorithms were safe and effective in correcting high myopia. Among them, the OPA algorithm maintained optical quality and physiologic cornea longer than the others.

193 nm excimer laser lift-off for AlGaN/GaN high electron mobility transistors

AlGaN/GaN HEMTs grown on both-side-polished sapphire substrates were successfully lifted-off with a 193-nm UV excimer laser system. The photon energy of the 193 nm laser is larger than the band gap of AlN and thus it can be used to lift-off AlGaN HEMT structures with AlN or AlGaN interfacial layers grown on sapphire substrates prior to growth of the GaN buffer layers. The lifted-off HEMT chip was warped and showed 25–42% reduction of the saturation drain current. There was no degradation observed either in the forward or reverse gate current-voltage (I-V) characteristics or on the drain punch-through voltage. Based on comparisons of cross-sectional electron micrographs, no additional dislocations were created in the HEMT structures after the laser lift-off process. Reduction in saturation drain current was attributed to relaxation of the lifted-off HEMT structures. Newton's rings and Raman spectrum E2 peak shifts were used to estimate the strain relaxation of the laser lifted-off samples.

GaN-based light-emitting diodes on origami substrates

GaN-based light-emitting diodes (LEDs) were transferred to paper substrates after a laser lift-off (LLO) process with an ArF excimer laser system (λ = 193 nm) to remove the sapphire substrate and produce freestanding blue LED templates. The threshold voltage (∼2.7 V), current-voltage characteristics, and peak emission wavelength (442 nm) were not changed after the paper substrate was subsequently wrinkled. We were able to demonstrate transfers to both planar and folded (origami) paper structures, showing the promise of the LLO process for transferring LEDs to arbitrary surfaces.

Aspheric photorefractive keratectomy for myopia and myopic astigmatism with the SCHWIND AMARIS laser: 2 years postoperative outcomes

PurposeTo evaluate mid-term refractive outcomes and higher order aberrations of aspheric PRK for low, moderate and high myopia and myopic astigmatism with the AMARIS excimer laser system (SCHWIND eye-tech-solutions GmbH, Kleinostheim, Germany). MethodsThis prospective longitudinal study evaluated 80 eyes of 40 subjects who underwent aspheric PRK. Manifest refractive spherical equivalent (MRSE) of up to −10.00 diopters (D) at the spectacle plane with cylinder up to 3.25 was treated. Refractive outcomes and corneal wavefront data (6mm pupil to the 7th Zernike order) were evaluated out to 2 years postoperatively. Statistical significance was indicated by P<0.05. ResultsThe mean manifest spherical equivalent refraction (MRSE) was −4.77±2.45 (range, −10.00D to −0.75D) preoperatively and −0.12±0.35D (range, −1.87D to +0.75D) postoperatively (P<0.0001). Postoperatively, 91% (73/80) of eyes had an MRSE within ±0.50D of the attempted. No eyes lost one or more lines of corrected distance visual acuity (CDVA) and CDVA increased by one or more lines in 26% (21/80) of eyes. Corneal trefoil and corneal higher order aberration root mean square did not statistically change postoperatively compared to preoperatively (P>0.05, both cases). There was a statistical increase in postoperative coma (+0.12μm) and spherical aberration (+0.14μm) compared to preoperatively (P<0.001, both cases). ConclusionAspheric PRK provides excellent visual and refractive outcomes with induction in individual corneal aberrations but not overall corneal aberrations.

Laser sheath for tunneled dialysis catheters extraction

The number of patients with acute renal failure and end-stage renal disease undergoing hemodialysis (HD) has increased during the past years, and the management of vascular access is pivotal. Among tunneled dialysis catheters (TDC), Tesio twin-catheter system (Medcomp, Harleysville, PA, USA) provides good long-term survival with acceptably high blood flow and low complication rates [1, 2]. Unfortunately, catheter infection is still a serious and common complication related to temporary HD vascular access. When catheter infection and/or dysfunction occur, extraction is mandatory [3]. Although the development of a fibro-epithelial sheath is a common occurrence, TDC extraction is usually easily performed by traction or cut down technique [3, 4]. However, when the catheters are tethered or attached to central veins and/or to right atrium, these techniques could lead to their rupture and retention and could increase the risk of vascular or atrial wall avulsion. Laser extraction technique is usually adopted for pacing leads, but it can also be helpful in TDC extraction to avoid the previous mentioned complications. A circumferential Excimer laser beam applied at the tip of a specialized telescopic sheath is passed over the lead. The energy source comes from a xenon chloride laser with an output wave length of 308 nm. It is a cool cutting laser (50 C) with a very limited absorption depth; twothirds of the energy are absorbed within 0.06 mm from the tip of the sheath by proteins and lipids instead of water. These technical characteristics allow the ablation of the fibro-epithelial sheath surrounding TDC without damaging the endothelial wall and the catheter itself [5]. According to these assumptions, our laboratory has decided to adopt this technique to extract tethered TDCs. A woman of 57 years, affected by endstage renal disease, was admitted to our Department for a Tesio twin-catheter system-associated bacteraemia. A transesophageal echocardiographic evaluation showed a thrombus occluding the apex of the right atrial appendage. A valvular involvement was excluded. After 2 months of oral anticoagulation therapy, she underwent TDC extraction performed using an Excimer Laser system emitting energy at the tip of a flexible, fiber-optic 12F-sheath (Spectranetics Inc., Colorado Springs, CO, USA). The procedure was performed under assistant sedation with i.v. midazolam. First, the TDC was isolated. Then, an A. Curnis L. Bontempi M. Cerini F. Vassanelli A. Lipari N. Ashofair C. Pagnoni L. Dei Cas Division of Cardiology, EP Lab, Post Graduate School of Cardiology, Spedali Civili, University of Brescia, Brescia, Italy

Stability of Therapeutic Retreatment of Corneal Wavefront Customized Ablation With the SCHWIND CAM: 4-year Data

To evaluate the long-term outcomes of aspheric corneal wavefront ablation profiles for excimer laser retreatment. Eighteen eyes that had previously undergone LASIK or photorefractive keratectomy (PRK) were retreated with LASIK using the corneal wavefront ablation profile. Custom Ablation Manager (SCHWIND eye-tech-solutions, Kleinostheim, Germany) software and the ESIRIS flying spot excimer laser system (SCHWIND) were used to perform the ablations. Refractive outcomes and wavefront data are reported up to 4 years after retreatment. Pre- and postoperative data were compared with Student t tests and (multivariate) correlation tests. P<.05 was considered statistically significant. A bilinear correlation of various postoperative wavefront aberrations versus planned correction and preoperative aberration was performed. Mean manifest refraction spherical equivalent (MRSE) before retreatment was -0.38±1.85 diopters (D) and -0.09±0.22 D at 6 months and -0.10±0.38 D at 4 years postoperatively. The reduction in MRSE was statistically significant at both postoperative time points (P<.005). Postoperative aberrations were statistically lower (spherical aberration P<.05; coma P<.005; root-mean-square higher order aberration P<.0001) at 4 years postoperatively. Distribution of the postoperative uncorrected distance visual acuity (P<.0001) and corrected distance visual acuity (P<.01) were statistically better than preoperative values. Aspheric corneal wavefront customization with the ESIRIS yields visual, optical, and refractive results comparable to those of other wavefront-guided customized techniques for the correction of myopia and myopic astigmatism. The corneal wavefront customized approach shows its strength in cases where abnormal optical systems are expected. Systematic wavefront customized corneal ablation appears safe and efficacious for retreatment cases.

Laser‐SNMS investigations on pyrene using Ga+, Bi1+, Bi3+ and Bi5+ as primary ions and different laser wavelengths and laser power densities for photoionization

Laser secondary neutral mass spectrometry (Laser‐SNMS) has been used to simultaneously ionize sputtered secondary neutrals in a nonselective way. To investigate the sputtering and photoionization processes, we examined the dependence of the Laser‐SNMS molecular yield on (i) different primary ion bombardment conditions using mono‐ and polyatomic ions and (ii) the laser parameters wavelength and laser power density. The Laser‐SNMS experiments were carried out using Ga+, Bi1+, Bi3+ and Bi5+ as primary ions and two different excimer laser systems for photoionization working at wavelengths of 157 and 193 nm, respectively, with power densities varying between 4 × 106 and 4 × 108 W/cm2. It was found that Bi3+ as primary ion is most suited to investigate organic surfaces. The highest yields could be obtained using a laser wavelength of 157 nm after ionization. Copyright © 2012 John Wiley &amp; Sons, Ltd.

U-Pb dating of zircon by laser ablation ICP-MS: recent improvements and new insights

A robust method for U-Pb dating of zircon by laser ablation ICP-MS was established using a Thermo-Finnigan Element2 sector field ICP-MS coupled to a New Wave UP193HE ArF Excimer laser system. This included the construction of a low-volume sample cell and the establishment of a data reduction routine. A detailed systematic approach for determining optimal ablation settings and ICP-MS parameters is presented, which is also applicable to other instrument set-ups. Laser induced time-dependent elemental fractionation is corrected using the intercept method, whereas instrument drift, mass bias and elemental fractionation caused by ionisation differences are corrected by applying external standardisation using the matrix-matched reference zircon GJ-1. The isobaric interference of 204Hg on 204Pb is reduced by using a gold trap enabling the application of an accurate common Pb correction. Typical laser craters are 12, 25 or 35 μm in diameter and ca . 20 μm deep. A single analysis takes 65 s and the automated analysis of a measurement sequence ensures optimal efficiency. The performance of the established procedure was assessed by analysing zircon ranging in age from Mesoproterozoic to Miocene. Concordia ages obtained from multiple analyses on the various well-characterised zircons are all within uncertainty of the accepted values, demonstrating the high accuracy of the method. The uncertainty on the individual ages ranges from 1 to 4 % (2σ), depending on the absolute age, Pb content and homogeneity of the analysed zircon. These results indicate that the precision and accuracy obtained using the technique presented in this study are similar to those of other LA-ICP-MS laboratories and SIMS analyses.

Wavefront-guided versus cross-cylinder photorefractive keratectomy in moderate-to-high astigmatism: a cohort of two consecutive clinical trials

BackgroundAlthough there have been many studies of the efficacy and safety of wavefront- guided (WF) and cross-cylinder photorefractive keratectomy (PRK), there are few studies on moderate-to-high astigmatism cases. The aim of this study was to assess and compare the efficacy of WF and cross-cylinder PRK in moderate-to-high astigmatism.MethodsIn a comparative cohort, the results of two before-and-after clinical trials conducted on moderate-to-high astigmatism were studied. In the first trial, 50 eyes of 25 patients with stable refraction were enrolled in a before-and-after clinical trial to undergo WF PRK using the VISX™ (VISX Inc, Santa Clara, CA) system. The second clinical trial enrolled 48 eyes of 24 patients with stable refraction and moderate-to-high astigmatism to undergo PRK by the cross-cylinder method using a NIDEK EC-5000 excimer laser system (NIDEK Co Ltd, Gamagori, Japan).ResultsAfter 6 months, 80% of the eyes in the WF group had uncorrected visual acuity of 20/20 or better compared to 40% in the cross-cylinder group. Only one eye in the cross-cylinder group and no eyes in the WF group lost more than one line of best corrected visual acuity (BCVA) after 6 months of treatment. No treated eyes in either group lost more than two lines of BCVA. The percentage of eyes with no change in BCVA was 54% and 58.3% in the WF and cross-cylinder groups, respectively. Mean postoperative absolute changes in total root-mean-square higher order aberrations in the WF group and cross-cylinder group were 0.05 ± 0.22 μm and 0.17 ± 0.20 μm, respectively (P < 0.001).ConclusionBoth methods of PRK, using the NIDEK EC-5000 and VISX excimer laser systems, are effective for correcting moderate-to-high astigmatism. The WF approach appeared more successful in improving the refractive results.

Conical Structures on Acrylic Intraocular Lens (IOLs) Materials after 193-nm Excimer Laser Ablation

Intraocular lens (IOLs) implants are synthetic lenses used to replace the natural lens of the eye and obtain optical reha- bilitation. The materials and methods of IOLs fabrication have been correlated with postoperative complications such as diffractive aberrations, capsular opacification or discoloration. Thus, several new materials and patterns are studied for the formation and etching of intraocular lenses (IOLs). In our work, we studied the use of UV laser as an alternative method to conventional surface shaping techniques for IOLs etching. Ablation experiments were conducted on hydrophobic acrylic IOLs by a commercial excimer laser system used in photorefractive surgery. The morphology of the irradiated area was observed by scanning electron microscopy (SEM) and a mathematical algorithm was used for SEM image processing. The effect of IOLs exposure to UV light before excimer laser irradiation was also examined, since natural ageing and cross-linking of IOLs material were reported. Conical structures were revealed after UV laser ablation and their population was increased with the number of laser pulses. Period distribution of cones was measured with the combination of image processing and a scanning algorithm which was developed for this reason. According to the graphs, the mean period and the distribution of the cones was depending of the number of irradiation pulses and the exposure to UV lamp before laser irradiation. Although a photochemical and a theoretically smooth-surface ablation mechanism is considered for the UV excimer laser interaction with polymers, surface conical-like abnormalities and thermal degradation of the lenses materials was observed.

Visual Outcomes After Epi-LASIK and PRK for Low and Moderate Myopia

To evaluate visual outcomes following epi-LASIK compared to photorefractive keratectomy (PRK). Of a total 294 patients aged ≥21 years, 145 (290 eyes) underwent epi-LASIK and 149 (298 eyes) underwent PRK for low to moderate myopia or myopic astigmatism. Epi-LASIK was performed with the Amadeus II epikeratome (Abbott Medical Optics) and PRK with the Amoils rotary epithelial brush (Innovative Excimer Solutions). All ablations were performed using the same excimer laser system. Outcome measures included intraoperative complications, corneal reepithelialization, postoperative pain, uncorrected distance visual acuity (UDVA), manifest refraction spherical equivalent (MRSE), corrected distance visual acuity (CDVA), corneal haze, and quality of vision. Mean preoperative MRSE was -2.97±1.19 diopters (D) for epi-LASIK versus -2.95±1.06 D for PRK. Complete reepithelialization was achieved by postoperative day 4 in 46.9% of epi-LASIK eyes versus 92.4% of PRK eyes, with superior UDVA at postoperative day 1 in the PRK group (P=.002). Using Fisher exact test, a significantly higher percentage of epi-LASIK eyes compared to PRK eyes achieved 20/15 or better at 1 month (25.8% vs 17.8%, P=.031), 3 months (62.3% vs 49.3%, P=.004), 6 months (77.1% vs 57.9%, P<.001), and 12 months (75.9% vs 61.9%, P=.002). A change in MRSE >0.50 D occurred in 8.4% of epi-LASIK eyes within the 3- and 12-month interval versus 17.7% of PRK eyes (P=.04). No differences were noted between the two procedures in CDVA or clinically significant haze. Epi-LASIK showed superior refractive efficacy and stability but required more time for wound healing, resulting in inferior early visual outcomes and a tendency to overcorrect higher refractive errors compared to PRK. Both treatments were safe and comparable in terms of pain and haze formation.

I‐LASIK retreatment of residual refractive errors after microkeratome and femtosecond assisted LASIK

AbstractPurpose To evaluate the efficacy and safety of femtosecond‐assisted sub‐bowman keratomileusis (I‐LASIK) retreatment for residual refractive errors after either I‐LASIK or microkeratome assisted LASIK.Methods We performed i‐lasik retreatment in 14 eyes of 10 patients (mean age 37) for residual myopic and astigmatic refractive errors after previous both i‐lasik and lasik procedures. All patients had stable residual refractive errors for at least 2 years. I‐lasik was performed in all cases with AMO's IntraLase™ FS and STAR S4 IR™ Excimer Laser System, corneal flap thickness was 100µm and hinge position was 90 degrees with reverse 120° side cut. The optical zone of the ablation was from 6.5 to 7 mm, transition zone from 8 to 9 mm.Results Controls were made at 1day, 1 and 3 months. Anterior segment OCT and corneal confocal microscopy were performed in every case. No flap decentration was observed in any case, we had 2 cases of epithelial ingrowth, 4 cases of dry eye, no cases of corneal ectasia and no retinal complications. All spherical equivalent results were within 0.50 diopters.Conclusion In our experience I‐lasik procedure demonstrated itself to be safe and effective also in patients with residual refractive errors from previous i‐lasik and lasik treatments.

Clinical observation of laser in situ keratomileusis (LASIK) with corneal flap created by femtosecond laser

Objective To investigate the safety, predictability and effectiveness of laser in situ keratomileusis (LASIK) with laser flap created by femtosecond laser. Methods 1016 eyes of 512 patients with refractive error received LASIK with vlSX Star S4 excimer laser system and Intralase femtosecond laser. The period of follow-up ranged from 6 to 12 months. The transparency of cornea and the refractive changes after surgery were examined by slit-lamp microscope and corneal topographic device. Results At 6 months after operation,the mean residual spheroequivalent of refraction was ( - 0.25±0.75 ) D ( range - 1.00D to +1.25D). 923 eyes (90.85%) had uncorrected visual acuity of 1.0 or better, 1002 eyes (98.62%) had uncorrected visual acuity equal to or better than preoperative best corrected visual acuity. The intraoperative complication was subconjunctival hemorrhage (57 eyes, 5.61% ) , and no other complications were found.Conclusion LASIK with corneal flap created by femtosecond laser is a safe and effective procedure for the correction of refractive error. It has good predictability. Key words: femtosecond laser; corneal flap; LASIK

高功率XeCl准分子激光系统前端平滑实验

The seed beam smoothing experiments were performed to get a smoothing and partial coherence seed by using Amplified Spontaneous Emission(ASE) and scattering methods.The relationship between the uniformity of seed beam intensity distribution,energy,the divergence of seed beam and the beam diameter and postion was investigated based on a short pulse XeCl excimer laser.And then the factors which infulenced the parameters of the seed beam were analysed.Experimental results indicate that the lowest nonuniformity of the seed beam produced by ASE method is 2.01%,and the energy is several μJ.But the horizontal divergence of the seed beam is different from the vertical one.The nonuniformity of the seed beam produced by scattering method is 1.54%,the energy is about one hundred nJ as the divergence is 5.5 mrad,and the laser beam diffraction limited times can be adjusted from 14 to 37.Furthermore,the size of the pumping source influences the divergence of the seed produced by ASE,and the input laser energy,laser diameter on scattering board and the focus of the lens for gathering light influence the parameters of scattering seed.After being amplified,the nonuniformity of the source beam is 2.04%,and the energy is about 8.0 mJ.The results mentioned above show that the seed adapts to the high power XeCl excimer laser system.

高功率准分子激光系统光学设计

高功率准分子激光系统光学设计