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At least 577 records · Page 32Linked to original sources
PubMed1984

Formation of peripheral anterior synechiae following argon laser trabeculoplasty. A prospective study to determine relationship to position of laser burns.

One hundred eighteen eyes with primary open-angle glaucoma underwent argon laser trabeculoplasty . Laser burns were placed in the anterior trabecular meshwork (ATM) in 58 eyes and directly over Schlemm's canal in the posterior trabecular meshwork (PTM) in 60 eyes. Twenty-nine eyes received 100 burns and 89 eyes received 50 burns distributed equally over 360 degrees. Peripheral anterior synechiae (PAS) developed in seven (12%) of the eyes having anterior trabeculoplasty and in 26 (43%) of those having posterior trabeculoplasty . There was no correlation between the development of PAS and sex, width of the anterior chamber angle, or the number of laser burns. Eyes having anterior trabeculoplasty had a final decrease in intraocular pressure equal to those having posterior trabeculoplasties . Our results strongly suggest that trabeculoplasty is a safer but no less effective procedure when the laser burns are placed on the ATM rather than the PTM.

Glaucoma, Open-Angle↗
PubMed1996

In vitro studies and computer simulations to assess the use of a diode laser (850 nm) for laser-induced thermotherapy (LITT).

BACKGROUND AND OBJECTIVE: This study investigated the feasibility of 850 nm diode laser-induced thermotherapy (LITT), a new procedure providing local hyperthermia and photocoagulation, a minimally invasive treatment of tumors, and other disorders such as benign prostate hyperplasia. STUDY DESIGN/MATERIAL AND METHODS: An improved fiber optic diffuser inserted through a catheter was used to irradiate prostate, liver, and kidney tissue in-vitro. Experimental results were compared with predictions from mathematical simulations based on measured optical tissue parameters. RESULTS: After 10 minutes of irradiation with 2-4.6 W CW laser power, sizable coagulation diameters had been achieved. In prostate and kidney tissue, temperature rises and coagulation diameters after laser irradiation were found to be smaller than in liver tissue. Those tissues also had a higher threshold for carbonization, thus reducing the risk of damage to the delivery system. CONCLUSION: The data suggest that a low power diode laser can be recommended for use in LITT to treat prostate and kidney tissue.

Animals↗
PubMed2004

Laser spray: electric field-assisted matrix-assisted laser desorption/ionization.

A new liquid chromatography/mass spectrometry interface, the laser spray, has been developed. Explosive vaporization and mist formation occur when an aqueous solution effusing out from the tip of the stainless-steel capillary is irradiated from the opposite side of the capillary by a 10.6 microm infrared laser. Weak ion signals could be detected when the plume was sampled through the ion sampling orifice. When a high voltage (3-4 kV) was applied to the stainless-steel capillary, strong ion signals appeared. The ion abundances were found to be orders of magnitude greater than those obtained by conventional electrospray ionization in the case of aqueous solutions. The present method is regarded as an electric-field assisted form of matrix-assisted laser desorption/ionization in which the liquid chromatographic solvent (water, etc.) acts as a liquid matrix. Laser spray ionization is expected to become a versatile method for biological mass spectrometry because this method is compatible with the natural solvent, water.

Electromagnetic Fields↗
PubMed1988

Non-invasive laser microsurgery selectively damages populations of labeled mouse neurons: dependence on incident laser dose and absorption.

Selective photothermolysis (SP) is a novel technique by which brief, unfocused laser pulses are selectively absorbed by, and cause selective thermal damage to, endogenously pigmented structures. This report describes the use of an exogenous non-fluorescent chromophore (Procion blue) to effect cellular damage by SP. Cultured dorsal root ganglia neurons were selectively labeled with Procion blue and subjected to varying doses of laser illumination. Progressive cellular damage was assessed by leakage of propidium iodide through damaged membranes. The neurons targeted via an exogenous chromophore sustained damage which was proportionate to laser dose and chromophore concentration. The results of these experiments demonstrated that the rate and extent of neuronal damage can be controlled by adjusting either the incident dose of laser energy or the amount of target chromophore within cells. Selective photothermolysis will provide an experimental tool for neurobiologists in particular and will find general use within the biomedical field.

Animals↗
PubMed1994

A two-year review of pain control during laser therapy using the flashlamp pulsed dye laser.

Laser therapy is now accepted as the treatment of choice for port wine stains. Patient reaction to laser light exposure and methods used to control pain during 1357 treatment sessions for 350 medium to large port wine stains using the SPTL-1 laser (Candela Laser Corporation) are reported. In the majority of cases (86%) it was necessary to use either general anaesthesia or some other form of local pain control.

Adolescent↗
PubMed2006

Comparison of the IntraLase femtosecond laser and mechanical microkeratome for laser in situ keratomileusis.

PURPOSE: To compare clinical outcomes between the IntraLase femtosecond laser and the mechanical microkeratome for creating flaps during laser in situ keratomileusis. DESIGN: Nonrandomized clinical trial. METHODS: The study involved a total of 55 eyes of 30 patients, with 27 eyes of 16 patients comprising the microkeratome group and 28 eyes of 14 patients comprising the IntraLase group. Refractive errors, visual acuity, higher-order aberrations, contrast sensitivity, and corneal sensitivity were compared between the two groups. RESULTS: There were no statistically significant differences between the two groups in terms of refractive errors and postoperative uncorrected visual acuity. There was no loss of best-corrected visual acuity in either group. The higher-order aberrations were similar in both groups (P > .05), except for spherical aberration, which was greater in the microkeratome group (P < .05). In the IntraLase group, the contrast sensitivity value at 12 and 18 cycles per degree under mesopic conditions was significantly improved at three months postoperatively (P < .05). The IntraLase group showed faster corneal sensitivity recovery compared with the microkeratome group, and corneal sensitivity in the peripheral area was nearly normalized at three months postoperatively in the IntraLase group. CONCLUSIONS: The femtosecond laser may have advantages over the microkeratome in the flap-making procedure. However, the IntraLase femtosecond laser failed to have significant superiority over the mechanical microkeratome in clinical outcomes, except for faster recovery of corneal sensation, lesser degree of spherical aberration, and some contrast sensitivity value.

Adult↗
PubMed2004

Effect of expanding the treatment zone of the Nidek EC-5000 laser on laser in situ keratomileusis outcomes.

PURPOSE: To evaluate the effect of expanding the treatment zone of the Nidek EC-5000 laser on postoperative visual acuity as well as night glare and halos after laser in situ keratomileusis (LASIK) using 4 ablation zone diameters. SETTING: Division of Ophthalmology, Evanston Northwestern Healthcare and Northwestern University Medical School, Glenview, Illinois, USA. METHODS: This prospective study comprised 301 eyes of 154 consecutive patients who had LASIK in 1 or both eyes using the Nidek EC-5000 laser by 1 surgeon with experience in keratomileusis and excimer laser refractive surgery. A 6.5 mm optical zone was used with a transition zone 1.0 mm larger than the pupil under scotopic conditions (7.5, 8.0, 8.5, or 9.0 mm). Targeted correction was calculated according to a customized clinical nomogram. All patients were queried about glare and halos preoperatively and 3 months postoperatively using a questionnaire assigning numeric values to the degree of perceived visual disturbance (0 = no glare or halos, 1 = minimal, 2 = moderate, 3 = severe). RESULTS: The baseline uncorrected visual acuity (UCVA) was 20/200 or worse in 293 eyes. The baseline best spectacle-corrected visual acuity was 20/20 or better. The mean preoperative refractive sphere was -6.33 diopters (D) +/- 2.80 (SD) (range -1.00 to -16.25 D) and the mean preoperative refractive cylinder, 0.86 +/- 0.83 D (range 0 to +3.25 D). Three months postoperatively, 78% of eyes had a UCVA of 20/20 and 99%, of 20/40 or better. Preoperatively, 94 eyes (31%) had glare and halos. At 3 months, glare, halos, or both were present in 19 eyes of 11 patients (6.3%) (P<.0001); in 14 eyes, patients reported less severe glare and halos postoperatively than preoperatively. CONCLUSIONS: The use of a peripheral transition zone 1.0 mm larger than the pupil under scotopic conditions resulted in a low incidence of glare and halos postoperatively and did not adversely affect visual acuity. There was no increase in postoperative complications including corneal ectasia.

Adult↗
PubMed2005

Enhancement outcomes after photorefractive keratectomy and laser in situ keratomileusis using topographically guided excimer laser photoablation.

PURPOSE: To evaluate the efficacy and safety of topographically guided excimer laser photoablation to retreat unsuccessful myopic and hyperopic photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK). SETTING: Eye Clinic, San Salvatore Hospital, University of L'Aquila, L'Aquila, Italy. METHODS: At least 3 months after primary PRK (Group A) or primary LASIK (Group B), 48 eyes of 42 patients were submitted to PRK or LASIK enhancements. The eyes were treated with an excimer laser linked to a computerized videokeratography unit with a topographically supported customized ablation workstation. RESULTS: The mean follow-up was 27.8 months +/- 8.2 (SD). In Group A, the uncorrected visual acuity (UCVA) changed from 0.5 +/- 0.7 logarithm of the minimum angle of resolution (logMAR) (range 20/600 to 20/200) to 0.1 +/- 0.7 logMAR (range 20/60 to 20/20); the mean best spectacle-corrected visual acuity (BSCVA) changed from 0.1 +/- 0.7 logMAR (range 20/50 to 20/20) to 0 +/- 0.7 logMAR (range 20/50 to 20/20) after the enhancement. In Group B, the UCVA changed from 0.7 +/- 0.8 logMAR (range 20/600 to 20/40) to 0.1 +/- 0.7 logMAR (range 20/40 to 20/20); the mean BSCVA improved from 0.2 +/- 0.8 logMAR (range 20/30 to 20/20) to 0 +/- 1.3 logMAR (range 20/25 to 20/20) after surgery. CONCLUSIONS: The enhancements using topographically guided excimer laser photoablation with a topographically supported customized ablation method resulted in satisfactory and stable visual outcome with good safety and efficacy after unsuccessful PRK and LASIK.

Adult↗
PubMed1984

Lasers in urology. I. Laser physics and safety.

Interest in the use of the laser in urology is increasing. A thorough understanding of the physical principles governing the laser will aid greatly in the choice of the proper laser for each indication. The tenets of laser safety are stressed, along with the current federal guidelines.

Environmental Exposure↗
PubMed2001

200 Hz flying-spot technology of the LaserSight LSX excimer laser in the treatment of myopic astigmatism: six and 12 month outcomes of laser in situ keratomileusis and photorefractive keratectomy.

PURPOSE: To evaluate safety, efficacy, predictability, and stability in the treatment of myopic astigmatism with laser in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK) using the 200 Hz flying-spot technology of the LaserSight LSX excimer laser. SETTING: SynsLaser Clinic, Tromsø, Norway. METHODS: This retrospective study included 110 eyes treated with LASIK and 87 eyes treated with PRK that were available for evaluation at 6 and 12 months, respectively. The mean preoperative spherical equivalent (SE) was -5.35 diopters (D) +/- 2.50 (SD) (range -1.13 to -11.88 D) in the LASIK eyes and -4.72 +/- 2.82 D (range -1.00 to -15.50 D) in the PRK eyes. The treated cylinder was 4.00 D in both groups. Eleven (8.5%) LASIK eyes and 8 (7.4%) PRK eyes had secondary surgical procedures before 6 and 12 months, respectively, and were excluded when the 6 and 12 month outcomes were analyzed. RESULTS: None of the eyes lost 2 or more lines of best spectacle-corrected visual acuity. Seventy-seven percent of the LASIK eyes and 78% of the PRK eyes achieved an uncorrected visual acuity of 20/20 or better; 98% in both groups achieved 20/40 or better. The SE was within +/-0.5 D of the desired refraction in 83% of the LASIK eyes and 77% of the PRK eyes; it was within +/-1.0 D in 97% and 98%, respectively. The cylinder correction had a mean magnitude of error of 0.04 +/- 0.31 D (range -0.96 to +0.85 D) in the LASIK eyes and 0.02 +/- 0.37 D (range -1.44 to +0.72 D) in the PRK eyes. Refractive stability was achieved at 1 month and beyond in the LASIK eyes and at 3 months and beyond in the PRK eyes. CONCLUSION: The outcomes of this study are comparable to those achieved with lasers that use small-beam technology with a lower frequency, as well as with other types of delivery systems. They suggest that the 200 Hz technology used in the LaserSight LSX excimer laser is safe, effective, and predictable and that with LASIK and PRK the results are stable when treating low to moderate myopia and astigmatism up to 4.0 D.

Adult↗
PubMed1988

Intraocular lens damage from Nd:YAG laser pulses focused in the vitreous. Part I: Q-switched lasers.

The damage resulting from laser-induced optical breakdown and plasma formation on or near an intraocular lens (IOL) has been well described, but there is another form of damage, not associated with optical breakdown, that can harm an IOL. The parameters that lead to this damage were investigated. Polymethylmethacrylate IOLs were irradiated by a Q-switched Nd:YAG laser beam focused so that plasmas were formed well clear of the IOL. Damage was induced in the volume of plastic through which the laser beam passed and was cumulative, not being visible until several laser pulses had passed through the lens. The number of pulses required to produce damage varied inversely with the distance between the IOL and the site of plasma formation. This damage is most likely to occur clinically when vitreous structures are targeted in the pseudophakic eye.

Humans↗
PubMed2007

Verifiable CPD paper: introduction, history of lasers and laser light production.

The word laser conjures in the mind's eye many aspects of what might be described as 'modern' life. The words 'powerful', 'precise' and 'innovative' complement our conception of the world in terms of technology, whereas patients often associate the words 'magical' and 'lightening quick' with the use of lasers in medical practice. The purpose of this series of articles is to explore the history and development of lasers, the integration of lasers into clinical dentistry and the safeguards as to their regulated use.

Dental Cavity Preparation↗
PubMed1999

Laser therapy of spider leg veins: clinical evaluation of a new long pulsed alexandrite laser.

BACKGROUND: The response of spider leg veins to laser or intense pulsed light therapy has generally been characterized by varying degrees of success and frequently inconsistent clinical response rates. OBJECTIVE: The purpose of this study was to examine the effectiveness of the 755 nm long pulsed infrared alexandrite (LPA) laser for the treatment of leg telangiectasias. METHODS: This study was constructed in four phases. Phase I examined 28 patients with variable sized telangiectasias using 5 treatment parameters (15 J/cm2 x 1 pulse, 20 J/cm2 x 1 pulse, 20 J/cm2 x 2 pulses, 20 J/cm2 x 3 pulses, or 30 J/cm2 x 1 pulse). Each patient received 3 treatments at 4 week intervals with the LPA. Patient diaries were obtained to examine the effects of the treatments. Subjective grading was performed at each follow-up visit by the investigators. Blinded objective grading was performed at the conclusion of the study by trained observers. Phase II examined the effects of these treatment parameters on varying vessel diameters. Vessels were grouped into small (<0.4 mm), intermediate (0.4-1.0 mm), and large (1.0-3.0 mm) subsets. Phase III examined the effects of a combination of LPA treatment followed by 23.4% hypertonic saline sclerotherapy. Subjective and blinded objective grading was used to determine improvement after a single treatment with the LPA at 20 J/cm2, single pulsed with a pulse duration of 5 or 10 msec followed by treatment with 23.4% hypertonic saline injected 3, 7, 14, or 28 days after laser therapy. Phase IV involved biopsies after LPA treatment alone at time intervals of immediately posttreatment and 5 and 21 days posttreatment. RESULTS: These evaluations revealed that the optimal treatment parameters for LPA therapy alone appeared to be 20 J/cm2, double pulsed at a repetition rate of one Hz. After 3 treatments at 4 week intervals, subjective grading indicated a 63% reduction in leg telangiectasias. Medium diameter vessels responded best with small vessel diameters responding poorly, if at all. The addition of 23.4% hypertonic saline sclerotherapy performed 3 to 7 days after laser therapy (LPA at 20 J/cm2, single pulsed with a pulse duration of 5 msec) produced 87% reduction in leg telangiectasias. Biopsies after LPA treatment revealed vessel wall endothelial cell necrosis at 5 days with fibrosis occurring at 3 weeks. The optimal clinical "window" for sclerotherapy seems to coincide with the period of endothelial cell necrosis. CONCLUSION: LPA therapy is most effective for leg telangiectasias 0.4-3.0 mm in diameter. This LPA technique is significantly improved with the addition of sclerotherapy.

Adult↗
PubMed1990

Application systems for intracorporeal laser-induced shockwave lithotripsy using the Nd:YAG Q-switched laser.

For laser-induced shockwave lithotripsy, the electromagnetic energy of a laser light pulse is converted intracorporeally into the acoustic energy of a shockwave. The lithotriptor is based on a specially developed, Q-switched Nd:YAG laser whose high power light pulses (70 mJ, 25 nsec) are coupled into a flexible quartz fiber with a core diameter of 600 mum. Using focusing elements, energy densities higher than 6 x 10 5 J m -2 can be achieved, resulting in an optical breakdown in water followed by a shockwave. As a result of different absorption mechanisms, the breakdown threshold can be decreased by placing a metallic target into the laser beam. The different shockwave formations of such optomechanical transducers have been measured. First clinical applications have been performed.

Equipment Design↗
PubMed1997

Laser irradiation of bone. I. An in vitro study concerning the effects of the CO2 laser on oral mucosa and subjacent bone.

The purpose of this study was twofold: first, to evaluate the histologic effects of CO2 laser irradiation on biopsies of porcine oral mucosa and underlying bone under conditions that simulate the applications of the laser during gingival surgery; and second, to evaluate the histologic effects on cortical bone following irradiation with increasing energy densities. Specimens consisting of mucosa and underlying bone were subjected to multiple passes of the laser beam in the same line of incision at energy densities ranging from 240 to 1,032 J/cm2. A second group of specimens consisting only of cortical bone was irradiated by a single pass of the laser at energy densities ranging from 40 to 2,062 J/cm2. In both groups the mean depth of ablation, width of surface damage, and widths of the zones of thermal necrosis and thermal damage were determined. Results showed a direct correlation between increasing energy density and/or number of energy beam passes and increasing depths of ablation and widths of surface damage. Further, more than three passes at 1,032 J/cm2 penetrated the mucosal layer to involve underlying bone. The mean depth of ablation for bone specimens following a single pass of the energy beam ranged from 0.02 mm at 160 J/cm2 to a maximum of 0.75 mm at 2,062 J/cm2. Using those energy densities most common to oral soft tissue surgery, the mean depth of ablation in bone specimens ranged from 0.17 mm at 240 J/cm2 to 0.28 mm at 640 J/cm2 to 0.35 mm at 1,032 J/cm2. All specimens regardless of tissue composition, energy density, or number of energy beam passes exhibited a distinct layer of residual carbonized tissue, a zone of thermal necrosis characterized by tissue coagulation, and a zone of tissue exhibiting thermal damage.

Animals↗
PubMedDate not supplied

Laser in situ keratomileusis for recurrent hyperopia following laser thermal keratoplasty.

PURPOSE: Laser thermal keratoplasty (LTK) has its main indication in the correction of hyperopia. However, regression of refractive effect following LTK is a limitation. Laser in situ keratomileusis (LASIK) may provide a good alternative to correct residual refractive errors. METHODS: Fifty hyperopic eyes with varying amounts of regression after LTK underwent LASIK. The Chiron Automated Corneal Shaper microkeratome was used to make a flap of 160 microm and laser ablation was performed with the Technolas 217 Planoscan excimer laser. Postoperative follow-up was 6 months. RESULTS: Mean spherical equivalent refraction improved from +2.92+/-1.60 D to +0.36+/-1.48 D. Mean best spectacle-corrected visual acuity changed from 0.78+/-0.14 before LASIK to 0.76+/-0.16 D 6 months after LASIK. Mean uncorrected visual acuity changed from 0.37+/-0.16 to 0.66+/-0.24. Forty-two percent (21 eyes) were within +/-0.50 D of intended correction, 60% (30 eyes) were within +/-1.00 D, and 76% (38 eyes) were within +/-2.00 D. After LASIK, confluent haze between previous LTK spots was observed in most eyes, as LASIK ablation took place at the sites of the LTK spots. CONCLUSIONS: LASIK after LTK is a good alternative for hyperopic regression. Predictability and efficacy are less than with primary LASIK for hyperopia, but the procedure is equally safe.

Adult↗
PubMed2006

Laser subepithelial keratomileusis for the correction of high myopia with the Schwind ESIRIS scanning spot laser.

PURPOSE: To investigate the efficacy of laser subepithelial keratomileusis (LASEK) for the correction of high myopia with the Schwind ESIRIS scanning spot laser (Schwind eye-tech-solutions Gmbh & Co, Kleinostheim, Germany). METHODS: Fifty-one patients (76 eyes) were treated with a mean preoperative spherical equivalent refraction of -7.55 diopters (D) (range: -6.0 to -10.75 D). All eyes received a LASEK technique using 15% alcohol with a 20-second application. RESULTS: An intact epithelial flap was obtained in 73 (96%) eyes. At 1 week, uncorrected visual acuity (UCVA) was > or =20/30 in 53 (70%) eyes and > or =20/60 in all eyes. At 6 months (n=76), the mean SE was +0.08 D (range: -1.00 to +1.875 D) with 73 (96%) eyes within +/-1.0 D of the intended correction and 60 (79%) eyes within +/-0.5 D. At 12 months (n=46), the mean SE was -0.07 D (range: -1.375 to +2.0 D) with 44 (96%) eyes within +/-1.0 D of the intended correction and 37 (80%) eyes within +/-0.5 D. Myopic cylindrical corrections were attempted in 68 eyes (range: -0.25 to -4.25 D) with vector analysis demonstrating a mean 85% correction. At last follow-up, UCVA was > or =20/20 in 47 (62%) eyes, > or =20/25 in 63 (83%) eyes, and > or =20/40 in 75 (99%) eyes. Three (4%) eyes gained two lines of Snellen decimal equivalent best spectacle-corrected visual acuity compared to preoperative levels, 68 (89%) eyes showed no change or gained one line, and 5 (7%) eyes lost one line. None lost more than one line. Only 2 (3%) eyes at 6 to 12 months had more than +1 axial corneal haze and 50 (66%) showed no evidence of haze on slit-lamp examination. CONCLUSIONS: Laser subepithelial keratomileusis for myopia up to -11.00 D with the Schwind ESIRIS laser provides good refractive and visual outcomes, with acceptable visual recovery and minimal complications.

Adult↗
PubMed2000

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

PURPOSE: To determine the effects of the incidental exposure of stents to pulsed 308 nanometer ultraviolet excimer laser energy. METHODS: 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. RESULTS: 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. CONCLUSION: 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.

Atherectomy, Coronary↗