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At least 595 records · Page 33Linked to original sources
PubMed2002

Laser angioplasty and laser-induced thrombolysis in revascularization of anomalous coronary arteries.

Acute coronary syndromes such as unstable angina and myocardial infarction are attributed to a pathophysiologic process that involves rupture of atherosclerotic plaque and subsequent thrombosis. Percutaneous intervention of anomalous coronary arteries in patients who present with acute coronary syndromes impose unique technical challenges related to the specific anatomic course and morphology of these vessels. Selection of appropriate guiding catheter configuration, choice of supportive guidewire, and proper delivery and activation of debulking devices and stents are important steps toward achieving adequate results. Excimer laser angioplasty is a debulking technology for removal of atherosclerotic plaque and associated thrombi. To date, application of laser angioplasty in anomalous coronary arteries is unreported. We herein present clinical data and discuss technical aspects related to performance of excimer laser angioplasty in three symptomatic patients with acute coronary syndrome, two having an anomalous right coronary artery and one with an anomalous circumflex artery. The delivery of laser energy in these cases resulted in rapid thrombolysis of an occlusive thrombus, successful debulking of the underlying atherosclerotic plaque, facilitation of adjunct balloon angioplasty and stenting, and ultimately, improved clinical condition.

Aged↗
PubMed1983

Laser cyclotrabeculospasis in the system of laser treatment in glaucoma.

Different methods of glaucoma treatment by laser have their specific indications and taken together can be considered a kind of "system." A new method of so-called laser cyclotrabeculospasis was developed for use in open-angle simple glaucoma. The anterior surface of the ciliary body (seen gonioscopically) is coagulated by a conventional (argon-gas) laser close to the scleral spur. Tractional pull onto the trabeculum and the inner wall of Schlemm's canal is a probable explanation for hypotensive effect of the procedure and the improved aqueous outflow. There is no risk of serious complications. The laser cyclotrabeculospasis was used clinically to limit the use of surgery, but potentially the method may have some advantages over therapy by drugs as well.

Ciliary Body↗
PubMed1993

[Laser treatment for the membranous cataract: the significance of pre-laser interferometric acuity].

Laser interferometer was used for the detection of interferometric acuity before and after membranous cataract disruption by Q--switched Nd: YAG laser in 23 patients (23 eyes). There was no significant difference between the interferometric acuity before and after laser surgery (p < 0.05). The postoperative corrected acuity was related positively to the preoperative one (p < 0.05). 65.2% of the eyes had a postoperative corrected acuity better than the postoperative interferometric acuity. These results show that laser interferometric acuity is a valuable method in the evaluation of postoperative visual acuity, but false negative and false positive ones should be considered under some circumstances. The interferometric acuity can be affected by aphakia (high refractive error).

Aged↗
PubMedDate not supplied

Comparative effects of exposure to different light sources (He-Ne laser, InGaAl diode laser, a specific type of noncoherent LED) on skin blood flow for the head.

BACKGROUND AND OBJECTIVE: This study assessed the effects of optic stimuli emitted by three different light sources on head skin blood flow. MATERIALS AND METHODS: The irradiation effects of the He-Ne laser (632.8 nm, 10 mW, total energy appr. 9.4 J), the InGaAl diode laser (670 nm, 60 mW, appr. 108 J) and monochromatic light (635 nm, 112.5 mW, appr. 202.5 J) were measured using laser Doppler technology. The corresponding fluences (energy densities) varied from 0.01 J/cm2 (He-Ne) to a range of 0.12-0.72 J/cm2 (InGaAl) and 0.22-1.36 J/cm2 (LED). The investigation was completed under single-blind, placebo-controlled conditions where the subjects (10 male healthy volunteers) were exposed on two occasions to the placebo (LED)-device against the laser (He-Ne or InGaAl). RESULTS: A short lasting vasodilation, a 54 per cent increase (p < 0.05) in skin blood flow was seen after the InGaAl irradiation (fluences between 0.12-0.36 J/cm2) whereas the non-coherent monochromatic irradiation (0.68-1.36 J/cm2) used in this particular study decreased blood flow by 36 per cent (p < 0.05). The He-Ne irradiation (0.01 J/cm2) had no effect. Skin temperature changes were insignificant. CONCLUSIONS: Skin blood flow changes seemed to be related more on radiant exposures then coherency.

Adult↗
PubMed1986

Q-switched neodymium-YAG laser iridotomy in patients in whom the argon laser fails.

We conducted a short-term prospective clinical study to evaluate Q-switched neodymium-YAG laser iridotomy in 33 eyes with pupillary block glaucoma in which the argon laser was unable to create an iridotomy. These eyes had chronic angle closure glaucoma (11 eyes), acute angle closure glaucoma (five eyes), pseudophakic pupillary block (seven eyes), uveitic pupillary block (three eyes), and contralateral eyes (five eyes); also included were both eyes of a patient with a head tremor. In all eyes, a patent iridotomy was created in one treatment session, with a mean of 5 +/- 5 pulses and a mean total energy of 55 +/- 120 millijoules. Complications included iridotomy closure (two eyes with preexisting active uveitis), focal nonprogressive corneal opacities (six eyes), and minimal bleeding from the iridotomy margin (12 eyes). Q-switched neodymium-YAG laser iridotomy appears to be an effective next step in the management of pupillary block glaucoma prior to surgical iridectomy when argon laser iridotomy fails.

Argon↗
PubMed1995

Excimer laser treatment for high and extreme myopia. The Melbourne Excimer Laser and Research Group.

OBJECTIVE: The excimer laser allows the controlled ablation of corneal tissue to correct refractive error. We assessed the efficacy of excimer laser treatment for persons with high (spherical equivalent between -5 and -10 diopters) and extreme (spherical equivalent greater than -10D) myopia. METHODS: Patients were assessed 1, 3, and 6 months postoperatively. A VisX Twenty/Twenty laser was used. Visual acuity, refraction, corneal clarity, and adverse reactions were evaluated at each visit. RESULTS: Six month follow-up data were available for 194 high myopes and 53 extreme myopes. Postoperative healing was similar for the two groups. Six months postoperatively, 89.2% of high myopes and 49% of extreme myopes were within 2D of planned refraction. At 6 months, 28% of high myopes had an uncorrected visual acuity of 20/20 and 71% had an uncorrected visual acuity of 20/40. Of extreme myopes, 4% had an uncorrected visual acuity of 20/20 and 30% had an uncorrected visual acuity of 20/40. Significantly more corneal haze was observed in the extreme myopes. Loss of 2 or more lines of best corrected visual acuity was observed in 13% of high myopes and 13% of extreme myopes at 6 months. CONCLUSIONS: Excimer laser photorefractive keratectomy is an alternative means of treating high and extreme myopia and can cause a significant reduction in myopia. There is a need to gather further information as more patients are followed up for greater time.

Adult↗
PubMed1997

Broad laser indentation surface for retinal laser photocoagulation using indirect ophthalmoscopic delivery.

Laser photocoagulation of the peripheral retina is an important part of the therapeutic options for treating many vitreoretinal disorders, such as diabetic retinopathy, retinopathy of prematurity, and vitreoretinal degeneration. When preequatorial retinal photocoagulation is required, indirect delivery of laser energy is preferable, whether applied in the office setting or as part of a sterile surgical procedure. The anterior retina is usually visualized by scleral indentation employing a conventional scleral indentor or muscle hook. Under these circumstances the retinal surface presented frequently is too small and irregular, making efficient laser delivery unnecessarily laborious, resulting in a variable uptake of laser energy.

Equipment Design↗
PubMed1992

Laser-assisted nerve repair. Laser-trimming of nerve ends with epineurial suture anastomosis.

Suture repair of cranial and peripheral nerves has reached a maximal level with the use of advanced microneurorrhaphy techniques; however, functional recovery of the repaired nerve is still often unsatisfactory due to misrouted axonal regrowth. Freeze-trimming the nerve ends prior to anastomosis has been shown to significantly improve fascicular alignment and subsequent functional recovery. This study assessed the feasibility of using laser energy to trim the nerve ends prior to suture anastomosis. The 302-nm excimer laser was used to trim the severed sciatic nerve ends prior to anastomosis in 28 rats. Scanning electron and light microscopy, horseradish peroxidase retrograde labeling, nerve conduction velocity, and functional recovery were assessed postoperatively. The excimer laser was able to trim the nerve ends flat thereby facilitating the coaptation and alignment of the nerve ends. Misrouting of axons occurred in both the laser-trim and control groups. Although this technique has theoretical advantages, no statistically significant improvement was demonstrated in this investigation. This may have been in part due to the small sample size, since a small increment of improvement was noted. It is possible, however, with continued refinements in technique that a functional improvement may be seen in subsequent studies.

Anastomosis, Surgical↗
PubMed1996

Double-frequency Nd:YAG laser vs. argon-green laser in the treatment of proliferative diabetic retinopathy: randomized study with long-term follow-up.

BACKGROUND AND OBJECTIVE: A randomized clinical trial using the argon-green (514 nm) and the double-frequency Nd:YAG (532 nm) lasers was carried out on 42 eyes with proliferative diabetic retinopathy (PDR), with the aim of assessing the long-term effects of double-frequency Nd:YAG panretinal photocoagulation (PRP). MATERIALS AND METHODS: Twenty-one eyes were randomized to argon laser treatment (ALT) and 21 to double-frequency Nd:YAG laser treatment (NdLT). The mean follow-up was 28.90 months (+/- 6.13) in the ALT group and 29.57 months (+/- 5.17) in the NdLT group. RESULTS: In the ALT group, 20 eyes (95.2%) showed regression of PDR and one eye (4.8%) enlargement of pre-existing new vessels. In the NdLT group, neovascularization regressed in 20 eyes (95.2%) and increased in one (4.8%). CONCLUSIONS: The long-term efficacy of double-frequency Nd: YAG laser PRP in the treatment of PDR thus appears to be similar to that of argon-green.

Adult↗
PubMed1997

Healing of laser incisions in rat dermis: comparisons of the carbon dioxide laser under manual and computer control and the scalpel.

BACKGROUND AND OBJECTIVE: The Computer-Assisted Surgical Techniques (CAST) program was researched to decrease lateral tissue damage and improve wound healing subsequent to laser incision. CAST differs from the traditional laser because it makes the incision in a discontinuous manner, allowing tissue to cool during the incision process. STUDY DESIGN/MATERIAL AND METHODS: The transient temperature changes in the tissue adjacent to the incision were measured with a thermocouple in a rat model. The subsequent wound healing was studied with histology and tensiometry. RESULTS: The thermal measurements demonstrated that all CAST settings were cooler than the continuous mode of laser incision. However, histology and tensiometric studies showed mixed results. CONCLUSION: This research demonstrates that CAST can be used in future surgical applications with no delay in wound healing as compared to the manually controlled laser. However, this study also finds no decrease in the wound healing time when using the CAST program.

Animals↗
PubMed1997

Effects of heterogeneous absorption of laser radiation in biotissue ablation: characterization of ablation of fat with a pulsed CO2 laser.

BACKGROUND AND OBJECTIVE: Physicians encounter several clinical situations in which fat must be removed. In this study, the characterization of fat ablation produced by a pulsed CO2 laser is reported. STUDY DESIGN/MATERIALS AND METHODS: An RF excited 800 microns pulsed CO2 laser operating at 10.6 microns was used to ablate fresh porcine fat. The heat of ablation and ablation threshold were determined using a mass loss technique. Absorption coefficients for fat and dermis were determined by attenuated total reflection spectroscopy. RESULTS: Threshold radiant exposure and heat of ablation for fat were calculated from the mass loss measurements to be 1.05 J/cm2 and 2.4 J/cm3, respectively. The absorption coefficients of fat and dermis at 10.6 microns were 250 and 780 cm-1, respectively. Pulsed CO2 laser ablation of fat caused ejection of fat droplets, which ignited after high fluence pulses. CONCLUSION: A pulsed CO2 laser can effectively ablate fat with a threshold fluence and efficiency comparable to other soft tissues. Our data suggest that fat ablation occurs primarily through the ejection of intact fat particles via the explosive vaporization of intervening water "lakes".

Adipose Tissue↗
PubMed1998

Bubble formation as primary interaction mechanism in retinal laser exposure with 200-ns laser pulses.

BACKGROUND AND OBJECTIVE: Retinal laser photocoagulation is generally performed by laser pulses of a few hundred milliseconds. The tissue interaction mechanism is a pure thermal interaction mechanism. As pulse duration gets shorter, different, non-thermal interaction mechanisms start to appear. The time domain for a change of tissue interaction mechanism seems to be in the ns and micros range. The goal of this study was to characterize the tissue interaction mechanism with 200-ns laser pulses, which approximate the thermal relaxation time of single melanin granules. MATERIALS AND METHODS: The retinas of 19 eyes of 10 rabbits were irradiated by 10 and 500 repetitive laser pulses (wavelength, 532 nm; repetition rate, 500 Hz; pulse duration, 200 ns; per pulse energy, 0-120 microJ; retinal spot size, 100 microm). The effects were evaluated by fluorescein angiography, ophthalmoscopy and by theoretical thermal calculations. Light microscopy and transmission electron microscopy were additionally performed on lesions irradiated by 500 pulses. RESULTS: Single pulse threshold energies for angiographic visibility were 3.5 microJ (10 pulses) and 2.1 microJ (500 pulses), for ophthalmoscopic visibility 9.0 microJ (10 pulses) vs. 8.6 microJ (500 pulses). At energy levels above ophthalmoscopic visibility macroscopically visible bubble formation inside the retina could be observed. This occurred at energy levels of 35 microJ (10 pulses) vs. 17 microJ (500 pulses). Microscopic evaluation of lesions irradiated with 500 pulses and energies at the angiographic threshold showed a damage primarily to the RPE. Additional outer segment damage of the photoreceptors could be found. A gap between damaged RPE cells and the outer segments could be repeatedly found as well as damaged RPE cells, which were detached from intact Bruch's membrane. Temperature calculation shows that temperatures above 100 degrees C may exist around single melanin granules. CONCLUSION: The studies suggest that RPE damage may occur by bubble formation around single melanin granules.

Animals↗
PubMed1999

Success of transmyocardial laser revascularization is determined by the amount and organization of scar tissue produced in response to initial injury: results of ultraviolet laser treatment.

BACKGROUND AND OBJECTIVE: Previous studies of transmyocardial laser revascularization have reported open channels after ultraviolet laser treatment and closed channels with infrared lasers. We speculated that differences in long-term channel patency were determined by the healing response to injury. METHODS: Channels were made in rat hearts with a frequency-tripled neodymium:YAG laser, at 5 and 10 mJ per pulse, by advancing an optic fiber through the myocardium, from the epicardium to the ventricular cavity. Several months later, we challenged the ability of the channel to supply blood by arterial occlusion and examined the channel structure with polarized light microscopy. RESULTS: Low-pulse energy was associated with lower patency, more fibrosis, and larger infarcts than was the higher energy. Open channels were surrounded by collagen fibers aligned parallel to the channel; in closed channels, fibers were aligned perpendicular to the original channel direction. CONCLUSION: The amount of initial injury and its repair determine channel patency and function.

Animals↗
PubMed1998

Laser wire for crossing chronic total occlusions: "learning phase" results from the U.S. TOTAL trial. Total Occlusion Trial With Angioplasty by Using a Laser Wire.

The Prima laser guidewire system (Spectranectics Corp., Colorado Springs, CO) consists of an 0.018" hypotube containing a bundle of 45-microm optical fibers coupled to a pulsed excimer laser operating at a tip fluence of 60 ml/mm2 and a repetition rate ranging from 25-40 Hz. This laser guidewire was specifically designed to cross total occlusions refractory to passage with conventional wires. The Prima wire was evaluated in a feasibility study at 15 U.S. centers. Following failure to cross a total occlusion with approved guidewires, the Prima wire was utilized in 179 patients. Average age of subjects was 61 yr. Lesion locations included left anterior descending (36%), right (45%), and circumflex (19%) coronary arteries. Mean angiographic age of total occlusions was 70 wk (range, 2-1,020 wk, median, 14 wk). The use of the Prima wire either solely or in combination with conventional guidewires resulted in successful crossing in 61% of these previously impenetrable occlusions. Failure of the device was commonly related to length of the occlusion and tortuosity along the occluded pathway. Major complications included myocardial infarction in 7 patients (3.9%), tamponade in 3 (1.7%), and death in 2 (1.1%). This "learning phase" pilot study confirmed the feasibility of a laser guidewire in chronic total occlusions that are resistant to passage of conventional guidewires. An extended registry at these investigative sites is planned.

Adult↗
PubMed1989

Laser Doppler flowmetry for bone blood flow measurements: helium-neon laser light attenuation and depth of perfusion assessment.

Laser Doppler flowmetry (LDF) has been successfully used in clinical and experimental settings to evaluate bone perfusion but unanswered questions regarding its capabilities and limitations still remain. This study was undertaken to determine absorption of He-Ne laser light (632.8 nm) and maximum depth for flow assessment (threshold thickness) under optimal conditions in bone. Light transmittance in bovine bone samples of femora and tibia was measured after each step of grinding and depth of penetration calculated. The threshold thickness was obtained by placing the same samples in a flow chamber where a solution of 2% latex circulated beneath; flow was detected by a laser Doppler probe resting on top of the sample. The results showed a significantly higher depth of penetration for trabecular than for cortical bone. A regression analysis showed a high correlation between the inorganic fraction of the bone and the depth of penetration. The maximum depth at which the laser Doppler probe can evaluate flow in bone conditions was found to be 2.9 +/- 0.2 mm in cortical bone, 3.5 +/- 0.3 mm in bone covered by 1 mm cartilage and 3.5 +/- 0.2 mm in trabecular bone. The study showed the limitations of LDF in bone and their correlations to various bone properties.

Animals↗
PubMed2001

Signal transduction pathways involved in low intensity He-Ne laser-induced respiratory burst in bovine neutrophils: a potential mechanism of low intensity laser biostimulation.

BACKGROUND AND OBJECTIVE: Low intensity He-Ne laser irradiation has been reported to induce respiratory burst of neutrophils for a long time, but the mechanism remains obscure. We speculated that it is mediated by some signal transduction pathways. STUDY DESIGN/MATERIALS AND METHODS: The protein tyrosine kinases (PTKs) inhibitor, genistein, the phospholipase C (PLC) inhibitor, U-73122, and the protein kinase C (PKC) inhibitor, calphostin C, were used to probe signal transduction pathways of respiratory burst of bovine neutrophils which were induced by He-Ne laser at a dose of 300 J/m(2), respectively. RESULTS: The inhibitor of PTKs can completely inhibit the He-Ne laser-induced respiratory burst of neutrophils. PLC and PKC inhibitors can obviously reduce it, but not fully inhibit it. CONCLUSION: These results suggest that PTKs play a key role in the He-Ne laser-induced respiratory burst of neutrophils and [PTK-PLC-PKC-NADPH oxidase] signal transduction pathways may be involved in this process.

Animals↗
PubMed1985

Retinal effects of the frequency-doubled (532 nm) YAG laser: histopathological comparison with argon laser.

Retinal lesions produced in Dutch Cross rabbits with a frequency-doubled (532 nm) YAG laser in single pulse mode (30-100 microJ) and in train of uniform pulses (2.6 and 7.5 mJ) underwent histopathological examination by light and electron microscopy. The results were compared to argon laser lesions (11 and 15 mJ) in the same animals. Low-energy single-pulse YAG lesions produced separation of the neural retina from the retinal pigmented epithelium (RPE), while higher energies caused severe disruption of retinal structures with moderate damage to the RPE. A striking and consistent finding of all the single-pulse lesions was the presence of red blood cells between the RPE and neural layers. The findings appear to support a process of mechanical disruption. In contrast, the lesions produced by a uniform train of pulses showed well-defined damage to RPE and photoreceptors with no red blood cells between these two layers, no choroidal damage, and relatively little disruption of the inner retina. The typical argon lesion evidenced cellular damage from the RPE through all retinal layers. Leukocytes in the choroid contained "holes" or vacuoles not seen in YAG lesions. Both the uniformly pulsed YAG laser burst and argon laser produced effects consistent with a thermal process. Some differences between argon and YAG burst were observed. The results suggest that there may be a clinical potential for the 532-nm burst YAG in treating retinopathies.

Animals↗
PubMed1986

The low-output carbon dioxide laser for cutaneous wound closure of scalpel incisions: comparative tensile strength studies of the laser to the suture and staple for wound closure.

The low-output carbon dioxide (CO2) laser was used for cutaneous wound closure of scalpel incisions. Cutaneous scalpel incisions were placed over the dorsum of three minipigs and were then closed by either the laser, sutures, or staples. At multiple time points after wound closure, up to day 90, the tensile strengths of these wounds were comparatively evaluated. All wounds, including those closed with the laser, clinically appeared to heal similarly with no evidence of wound dehiscence or infection. Tensile strength studies revealed similar sigmoid curves for all wound closure modalities with low initial tensile strengths up to days 14 to 21, which afterwards increased rapidly, with a plateau toward day 90. From our study, it appears that the CO2 laser, in the low-output mode, can be used for cutaneous wound closure and that similar clinical healing and tensile strength measurements are obtained relative to the conventional cutaneous wound closure modalities of the suture or staple.

Animals↗