Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Lasers”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 181 records · Page 10Linked to original sources
PubMed1995

[Revision of the stapes foot plate with various laser systems. 1: Continuous laser irradiation].

During stapedotomy, the small dimensions and highly sensitive anatomic structures present require the highest degree of precision and safety. The risk of damage to middle and inner ear structures through manipulation with conventional instruments can be reduced by non-contact perforation of the footplate with the laser beam. The present study was devised to clarify which of the presently available laser systems was best suited for use in stapes surgery and thus represent a significant alternative to conventional stapedotomy. Isolated human stapes and bovine compact-bone platelets were used to investigate the connections between the parameters of various laser systems and their effects on bone tissue. The aim was to optimize the laser parameters required to achieve a perforation of 500 microns to 600 microns in diameter. In addition, the thermal effects of laser irradiation were assessed. Three different systems were employed: the argon and CO2 lasers in continuous wave (cw) modes and the CO2 laser in superpulse mode. The lasers investigated offered the advantage of achieving an adequately large perforation with one or a few juxtaposed applications but caused in part extensive thermal side effects at the stapes footplate. To reduce thermal effects, footplate perforation was best performed by several juxtaposed single shots at low power, short pulse duration and small beam diameter. The suitability of the argon laser for stapedotomy was rendered doubtful in view of the lower absorption coefficient of the stapes for the argon laser beam and the considerable influence exerted by the degree of pigmentation of the irradiated tissue sites with a resultant poor reproducibility of the perforation diameter.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

[Thermal stress of the inner ear during laser stapedotomy. I: Continuous-wave laser].

As a consequence of perforating the footplate during laser stapedotomy, direct radiation to the inner ear will warm perilymph and adjacent structures. To determine the possible thermal dangers to cochlear structures from different laser parameters, heat transport mechanisms, temperature increases and temperature fields were investigated in a model system approximating caloric and physiologic changes in the inner ear. The temperature-time course of local cochlear warming showed a rapid convection-dependent increase that reached a peak at about the end of the laser impulse. An increase in power density caused an elevation of the temperature in all laser systems used. Maximum temperatures varied widely for CO2 lasers at the same wave-length, but a different beam-time behavior was found at a distance of 2 mm behind the perforation by using low-power densities. Heat values were lowest at a pulse duration of 50 ms in the superpulse (< 5 degrees C) and continuous wave (cw) modes (< 9 degrees C), while the highest value was found in the pulser mode (to 21 degrees C). After argon laser irradiation at high-power densities, temperatures were nearly independent of location (5.5-13 degrees C). When considering risks of possible inner ear damage from thermal stress during laser stapedotomy, application of the CO2 superpulse and cw laser appears to be safe over a large power-density range. Low energies using a small-beam diameter and short pulse durations (50-100 ms) are recommended. In contrast, use of the CO2 laser in a pulser mode may result in inner-ear damage because of the high temperatures produced. Structures located at a greater distance can be endangered by direct irradiation with the argon laser.

Body Temperature Regulation↗
PubMed1998

Acute results, complications, and effect of lesion characteristics on outcome with the solid-state, pulsed-wave, mid-infrared laser angioplasty system: final multicenter registry report. Holmium:YAG Laser Multicenter Investigators.

BACKGROUND AND OBJECTIVE: The solid-state, mid-infrared holmium:YAG laser (2.1 microm wavelength) is a relatively new percutaneous device that has recently been evaluated in a multicenter study. Because of its unique wavelength and photoacoustic effects on atherosclerotic plaques, this laser may be useful in treatment of symptomatic patients with coronary artery disease. This study sought to evaluate the safety and efficacy of mid-infrared laser angioplasty in the treatment of coronary artery lesions. PATIENTS AND METHODS: Laser angioplasty was performed on 2,038 atherosclerotic lesions in 1,862 consecutive patients with a mean age of 61 +/- 11 years. Clinical indications included unstable angina (69%), stable angina (20%), acute infarction (6%), and positive exercise test (5%). Complex lesion morphology included eccentricity (62%), thrombus (30%), total occlusion (27%), long lesions (14%), and saphenous vein grafts (11%). RESULTS: This laser catheter alone successfully reduced stenosis (>20%) in 87% of lesions. With adjunct balloon angioplasty, 93% procedural success was achieved. The presence of thrombus within the target lesion was a predictor of procedural success (OR = 2.0 [95% confidence interval 2.0, 4.0], P = .04). Bifurcation lesions (OR = 0.5 [95% confidence interval 0.2, 1.0], P = .05) and severe tortuosity of the treated vessel (OR = 0.4 [95% confidence interval 0.2, 0.9], P = .02) were identified as significant predictors of decreased laser success. Calcium within the lesion was associated with reduced procedural success (OR = 0.57 [95% confidence interval 0.34, 0.97], P = .03), and calcified lesions required significantly more energy pulses than noncalcified lesions (119 +/- 91 pulses vs. 101 +/- 86 pulses, respectively, P = .0002). Complications included in-hospital bypass surgery 2.5%, Q-wave myocardial infarction 1.2%, and death 0.8%. Perforation occurred in 2.2% of patients; major dissection in 5.8% of patients, and spasm in 12% of patients. No predictor of major complications was identified. Six-month angiographic restenosis was documented in 54% of patients, and clinical restenosis occurred in 34% of patients. CONCLUSION: Mid-infrared laser has a safety profile similar to that of other debulking devices. This laser may be useful in select patients presenting with acute ischemic syndromes associated with intracoronary thrombus; however, like other coronary lasers, it is limited by the need for adjunctive balloon angioplasty and/or stenting to achieve adequate final luminal diameter. No beneficial effects on reducing 6-month restenosis rates were observed.

Aluminum Silicates↗
PubMed2000

Laser-tissue interaction with a continuous wave 3-mcm fibre laser: preliminary studies with soft tissue.

BACKGROUND AND OBJECTIVE: Lasers operating at wavelengths in the mid-infrared region have become increasingly popular for applications in areas of surgery and medicine. Advances in fibre laser technology have introduced a highly efficient, compact, diode-pumped source operating at around the 3-mcm wavelength. This study examines the effects of this recently developed laser on soft biological tissue. STUDY DESIGN/MATERIALS AND METHODS: Chicken breast and liver tissue samples were exposed to 800 mW continuous wave laser power, at a wavelength of 2.71 mcm, with incident spot sizes of around 150 mcm. Samples were inspected grossly immediately after laser irradiation and also prepared for histologic processing. RESULTS: After irradiation, visual assessment of changes at sample surfaces indicated a region of thermally affected tissue surrounding the ablation crater. This region was observed to grow in size to around 1.0 mm in diameter after 3 seconds of laser exposure at 800 mW. An ablation velocity of 0.80 mm.s(-1) was determined in chicken breast for the same incident laser parameters. Analysis of samples irradiated at 800 mW and processed for histology revealed minimal damage at hole boundaries and no signs of char formation, providing incident exposure times were restricted to below around 0. 5 seconds. CONCLUSION: This fibre laser source has demonstrated its potential to fulfil medical applications, enabling accurate, precise tissue removal to proceed at a rapid ablation rate. The efficiency and small size of the laser are attractive features.

Animals↗
PubMed2002

Enamel caries initiation and progression after argon laser irradiation: in vitro argon laser systems comparison.

OBJECTIVE: The purpose of this in vitro laboratory study was to determine the effect of low-fluence argon laser (AL) irradiation delivered from two different argon laser systems on enamel caries-like lesion initiation and progression. BACKGROUND DATA: Previous in vitro investigations and a recent in vivo pilot study have shown that AL irradiation of enamel provided a protective effect against in vitro and in vivo cariogenic challenges. MATERIALS AND METHODS: Twenty extracted human molars were selected, and 10 teeth were assigned to the HGM argon laser group and 10 were assigned to the LaserMed argon laser group. The exposed buccal windows of sound enamel were exposed to low-fluence irradiation, while the lingual windows of enamel were not exposed to laser irradiation and served as the no-treatment (control) group. Enamel caries-like lesions were created using an acidified gel. Two longitudinal sections were taken per sample (n = 20 lesions per group) and evaluated by polarized light microscopy for body of the lesion depths after lesion initiation (8 weeks) and progression (12 weeks) periods. RESULTS: After lesion initiation and progression, the body of lesion depths were similar for both argon-irradiated groups (p > 0.05). With the no-treatment (control) group, there were significant increases in lesion depth with a 61-78% increase for the lesion initiation period and a 50-69% increase for the lesion progression period when compared with the argon laser-treated groups. CONCLUSION: Argon laser irradiation provides a certain degree of protection against in vitro enamel caries initiation and progression. Resistance to a continuous caries challenge was similar with either argon laser delivery systems (HGM and LaserMed). Argon laser irradiation may prove to be beneficial in reducing the caries susceptibility of sound enamel and white spot lesions in the clinical environment.

Argon↗
PubMed2005

An overview of the use of lasers in general dental practice: 1. Laser physics and tissue interactions.

High tech dentistry now involves the routine use of lasers in general dental practice for various procedures once thought only possible with the conventional dental drill or scalpel. In 1990, the first dental laser, the dLase 300 (American Dental Lasers, Corpus Christi,TX 78405 USA), was introduced to the profession. There are now many different types of laser used in dentistry using a variety of wavelengths. Each laser wavelength is absorbed differently by soft and hard tissues and the efficiency of the laser has been determined by the ability of the tissue to absorb or reflect that wavelength. This and the following article hope to give a broad overview of dental lasers and their clinical uses. This article gives an overview of the relevant laser physics and highlights the laser-tissue interactions.

Absorption↗
PubMed1998

Laser-assisted neuroendoscopy using a neodymium-yttrium aluminum garnet or diode contact laser with pretreated fiber tips.

OBJECT: Although lasers have proved to be valuable in neuroendoscopy, surgeons are still not comfortable using high-energy laser endoscopic probes in proximity to vital structures such as the basilar artery in third ventriculostomy. The authors have developed a special laser catheter for use in neuroendoscopy; the object of this paper is to present their experimental and clinical experiences using the catheter. METHODS: This laser catheter is fitted with an atraumatic ball-shaped fiber tip that is pretreated with a layer of carbon particles. These carbon particles absorb approximately 90% of the energy emitted, which is very effectively converted into heat. As the heat is generated in this very thin layer of carbon coating, the temperature at the surface of the ball-shaped tip reaches ablative temperatures instantly at powers of only a few watts per second, which has enabled the authors to limit drastically the amount of laser light used and the length of exposure needed, thereby increasing safety even around critical structures. CONCLUSIONS: The authors present experimental data and their clinical experience using these pretreated fiber tips with a neodymium-yttrium aluminum garnet contact laser or a diode contact laser in 49 patients (22 males and 27 females) and a variety of procedures: third ventriculocistemostomy (33 patients), cyst fenestration (nine patients), colloid cyst resection (six patients), and fenestration of the septum pellucidum (one patient). There was no instance of mortality or increased morbidity. To date, the procedure success rate is 100% and the overall outcome success rate is 86%. The authors conclude that pretreated atraumatic ball-shaped fiber tips now make laser application safe and effective in a variety of neuroendoscopic procedures. Because of their low power range (only several watts), compact diode lasers will be the energy source of first choice.

Adolescent↗
PubMed2002

[Lasers in dentistry 4. Removal of carious tissue using lasers].

Many lasers are available today for clinical application in dentistry. For the removal of caries in enamel or dentin only few lasers can be used. Er:YAG lasers have a wavelength that coincides with the absorption maximum of water. Because of this characteristic the ablative effect in enamel and dentin is high and these lasers can be used beneficially for caries removal and small preparations. The possible side effects of Er:YAG lasers with water-cooling are minor compared to those of rotary instruments. A pulpal reaction will occur only if there is a very thin dentin layer over the pulp or direct application of the laser beam to the pulp. There is no increased heating with the Er:YAG laser so with vital teeth there is a positive reaction by the formation of reparative dentin. To the existing indications for lasers like caries removal and preparation of small cavities, in the future new techniques can be added like the use of dyes for enhancement of absorption of the laser radiation, and minimal invasive techniques using feedback from a system for caries detection.

Dental Caries↗
PubMed1995

Clinical investigation of the combination of a scanning laser ophthalmoscope and laser Doppler flowmeter.

In this report we present the clinical applications of a new noninvasive method of imaging in high definition the topography of perfused retinal vessels. By the combination of a laser Doppler Flowmeter with a scanning laser system the retinal circulation can be visualized and quantified. The principles of measuring blood flow by laser Doppler flowmetry are based on the laser Doppler effect: laser light scattered by a moving particle is shifted in frequency. The scanning laser system is a modified laser scanning tomograph (technical data: retinal area of measurement, 2.7 x 0.7 mm; 10 degrees field with 256 points x 64 lines; horizontal digital resolution, 10 microns; wave-length, 670 nm; light power, 100 micro W; data acquisition time, 2.048 s). Every line is scanned 128-times at a line-sampling rate of 4000 Hz. By the performance of discrete fast fourier transformation over 128 intensities of each retinal point the laser Doppler shift is calculated for each retinal point. With these data a 2-dimensional map of the retinal perfusion with 256 x 64-points is created. The brightness of the picture point is coded by the value of the Doppler shift. By this method we examined health eyes with normal intraocular pressure (IOP) and artificially increased IOP and eyes with glaucomatous optic nerve atrophy, proliferative diabetic retinopathy with areas of capillary occlusion, arterial hypertension with microinfarction of the retina, and central retinal artery occlusion. The application of "scanning laser Doppler flowmetry" (SLDF) leads to the visualization of perfused vessels and capillaries of the retina in high resolution. The examination of perfused retinal arterioles, veins, and capillaries by this method represents the anatomical situation. In SLDF the area of normal or impaired retinal circulation becomes visible (capillary nonperfusion, proliferative vascular structures), whereby the extent of the perfusion is proportional to the brightness of the imaged vessel; the brighter the vessels or capillaries, the higher the blood flow inside the vessels. Retinal areas with low capillary flow are "dark" and show no visible vessel. In imaging of an eye with central retinal artery occlusion, retinal arterioles, veins, or capillaries were invisible due to the lack of retinal perfusion. Only ciliary-source vessels of the optic nerve head were bright and visible, indicating normal ciliary circulation. SLDF facilitates the visualization of perfused retinal capillaries and vessels in high resolution. The representation of the function of the retinal circulation by SLDF leads to an image similar to the anatomical situation. The two-dimensional mapping of local blood flow leads to a physiological picture of the retinal perfusion with visible vessels and capillaries.

Adult↗
PubMed1996

Tendon repair by laser welding: a histologic and biomechanical comparison and suture repair with CO2 and argon lasers.

BACKGROUND AND OBJECTIVE: The purpose of this study was to determine whether welding of tendinous tissue is possible with the application of thermal lasers. STUDY DESIGN MATERIALS AND METHODS: After sharp transection of a unilateral achilles tendon, 40 male outbred Spraque Dawley rats were divided equally between four treatment groups. Ten animals underwent repair using the modified Kessler suture technique. The remaining animals underwent application of laser after the tendon edges were reapproximated and held in place with a vascular clamp. CO2 and Nd:YAG lasers were applied using 25% human albumin as a solder. Fluorescein dye was added to albumin and used as solder for the Argon laser. Biomechanical and histologic testing were performed immediately and 14 days postoperatively. RESULTS: Argon and CO2 lasers successfully fused the tendon ends together. However, immediately postoperative, the resultant tissue weld was tenuous and conventional tensile strength testing was not possible. At 14 days postoperatively, all modes of tendon repair resulted in tensile failure at consistently lower levels of tension than those required for the normal uninjured tendons. The ultimate tensile strength for the suture-repaired, CO2 laser welded, and Argon laser welded tendons were 74%, 59%, and 64% of the strength of the control tendons respectively. No statistically significant difference was found in the tensile strength among the three repair groups. Histologic evaluation at 14 days revealed the greatest degree of inflammatory response in those tendons repaired with the Argon laser. Those tendons repaired with suture demonstrated the least amount of inflammatory change. CONCLUSION: Our study demonstrates that welding of a tendon is possible with the application of laser energy. However, we were unable to produce a weld sufficient to withstand significant tensile loads in the immediate postoperative period.

Achilles Tendon↗
PubMed1999

Laser skin resurfacing using a frequency doubled Nd:YAG laser after topical application of an exogenous chromophore.

BACKGROUND AND OBJECTIVES: Although laser skin resurfacing performed with CO(2) or Er:YAG lasers is efficient, side effects such as prolonged postoperative erythema, delayed healing, scarring, and pigmentation, have been reported. These side effects are due to skin characteristics but also to variations of the thermal effects associated with laser skin resurfacing. The study aimed to evaluate a new laser resurfacing method based on a previous topical application of an exogenous chromophore in order to have reproducible thermal effects. MATERIALS AND METHODS: Exogenous chromophore consisted in carbon dispersed and mixed with film-forming polymers and water. The resultant solution was applied to the skin surface using an airbrush. Experimental evaluation was performed in vivo on hairless rat skin using the following parameters (532 nm, 2.7 W, 1 mm, 50-200 ms, 17.2-68.8 J/cm(2), single pass). Skin biopsies were taken to evaluate histological changes and to quantify epidermis ablation and dermal coagulation depth. Wound healing was followed up during 10 days. RESULTS: Total epidermis ablation was achieved with all pulse durations used. Dermal coagulation depth increased as a function of exposure time. Scar formation was correlated with dermal coagulation depth. CONCLUSION: The concept of applying a carbon-based solution onto skin in order to obtain laser light conversion into heat followed by heat transfer to the tissue is valid for laser skin resurfacing. By selecting exposure time, the thermal effects are predictable and dermal coagulation depth can be either that observed with a Er:YAG laser or that obtained with a CO(2) laser. Moreover, frequency doubled Nd:YAG laser, already used in dermatology for angiodysplasias treatment, could be easily used for resurfacing of periorbital or perioral zones.

Administration, Topical↗
PubMed2002

Airflow through the auxiliary line of the laser fiber prevents ignition of intra-airway fire during endoscopic laser surgery.

BACKGROUND AND OBJECTIVES: Ignition accidents during bronchoscopic laser irradiation have occasionally been reported, but the mechanisms responsible for the ignition accidents are not fully understood. We examined causative factors including ignition site, oxygen concentration, and role of airflow through the laser fiber. STUDY DESIGN/MATERIALS AND METHODS: Porcine muscle tissue was placed in a bottle and irradiated by laser under various conditions. Also, a piece of porcine muscle was wedged in a main bronchus of the isolated porcine lungs and irradiated by laser in the same way. RESULTS: Flashing occurred on the tissue exposed to the laser, and this flashing reached the ignition when the oxygen concentration was above 30%. Increasing airflow through the laser fiber prevented the ignition even at an oxygen concentration at 100%. CONCLUSIONS: In laser irradiation, the tissue exposed to the laser can be the ignition site of fire. Increasing airflow through the laser fiber was an effective technique to prevent airway fire.

Air↗
PubMed1991

Endoscopic thoracic sympathectomy: evaluation of pulsatile laser, non-pulsatile laser, and radiofrequency-generated thermocoagulation.

We describe a modified technique for percutaneous denervation of the thoracic sympathetic chain by laser to treat selected cases of sympathetic causalgia of the upper extremities. The technique involves transpleural ablation with laser under thoracoscopic guidance through the second or third intercostal space-anterior axillary line. We also compare four different modalities of endoscopic denervation: A xenon chloride excimer laser (308 nm, 35 mJ/pulse, 20 pulses/sec, 2.2 mm catheter tip), CO2 laser (14 W, CW, 2 mm spot size), Nd:YAG laser (88 W, CW, 3 mm spot size), and radiofrequency-generated thermocoagulation (3 W, CW, 2.1 mm catheter tip) by performing bilateral thoracic sympathectomy on 12 mongrel dogs (three dogs each). Criteria analyzed included duration of exposure, power density, total energy output, laser penetration and spread, gross morphology, and scanning electron microscopy (SEM) of the destroyed neural tissue. Total ablation of the inferior segment of the stellate ganglion and the T1-T2 nerve roots by excimer laser required 83 +/1 1 Joules over an exposure period of 118 seconds. Ablation by CO2 and Nd:YAG laser required 153 +/- 13 Joules and 554 +/- 47 Joules delivered over 11 and 6 seconds respectively. In contrast, ablation of the same volume of nerve tissue by RF required 810 +/- 50 Joules over 270 seconds. SEM evaluation revealed that excimer and CO2 laser lesions were narrower in configuration compared to RF and Nd:YAG lesions which showed more lateral spread. The actual depth of penetration per 1 second exposure was similar for Excimer and CO2 (1.5 mm) and RF (1.3 mm), but deeper for Nd:YAG (3 mm).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2004

Laser cartilage reshaping in an in vivo rabbit model using a 1.54 microm Er:Glass laser.

BACKGROUND AND OBJECTIVES: The potential applications for facial laser cartilage reshaping (LCR) have generated increasing clinical interest. This study aimed to evaluate in vivo LCR of the rabbit ear using a 1.54 micro m Er:Glass laser in combination with contact cooling. STUDY DESIGN/MATERIALS AND METHODS: LCR was performed in vivo on 12 rabbit ears using a 1.54 micro m Er:Glass laser (Aramis, Quantel Medical, Clermont Ferrand, France) connected to a 4 mm chilled (+5 degrees C) handpiece placed in contact to the skin. Ear curvature was predetermined using a perforated cylindrical guide also used to standardize laser beam delivery. The treatment consisted of 15 spots (3 millisecond, 7 pulses, 12 J/cm(2), 2 Hz, 84/cm(2) cumulative fluence) applied on 10 contiguous parallel rows along the ear. After irradiation, the aluminum jig was replaced by a holder (10 mm diameter plastic tube) maintaining the curvature. This holder was secured with sutures and covered by an adhesive gauze bandage dressing to keep new form during 7 days. In order to assess thermal damage, biopsies were taken on irradiated areas and 1 week, 3 weeks and 6 weeks and studied using haematoxylin-erythrosin-safran (HES) and orcein staining and PCNA to detect cells in cycle. RESULTS: Using the laser with the parameters given above, no immediate visible effects were observed on the skin (no swelling, no bleaching). There were also no late visible side effects like crusting, or blistering. The laser treatment produced changes in the shape of every ear after the dressing was removed. A slight tendency to recover its initial shape was observed for each ear. However, the curvature was stabilized after 10 days and the average shape retention was 64+/-4% at 6 weeks, with a curvature radius of 7.25+/-0.75 mm, instead of 5 mm initially. Histological examination of the laser irradiated side at 1 week showed an intact epidermis. A reduced inflammation process was seen in the dermis. A modification of half of the layer of cartilage was observed at the opposite side where the laser irradiation was applied and proliferative cells were detected inside. At 3 weeks, an important chondroblastic proliferation was observed around the area of contracted cartilage. At 6 weeks, significant thickening of the cartilage layer was observed (from 300 to 490 micro m) and new chondrocytes were clearly seen. CONCLUSIONS: Rabbit ear cartilage can be reshaped with an Er:Glass laser. This technique could offer exciting possibilities that may help patients whose cartilage-lined joints have been affected by disease or trauma. This technique could be certainly utilized to correct alar cartilage deformities and septum deviation of cleft lips.

Animals↗
PubMed2005

Comparison of laser beam intensity profiles produced by photodynamic therapy (PDT) and transpupillary thermotherapy (TTT) lasers.

BACKGROUND AND OBJECTIVES: For photodynamic therapy (PDT) or transpupillary thermotherapy (TTT) lasers, long irradiation time (typically 1 minute or longer) is used and a large area of retina is treated. Consequently, the power stability but also the light distribution within the laser beam plays a major role. This study aimed to evaluate beam intensity profiles produced by several PDT and TTT lasers. STUDY DESIGN/MATERIALS AND METHODS: A beam profile analyzer (Cohu 4812 camera connected to a LPA-300PC, Spiricon, Logan, UT) was used to compare the beam profiles of PDT lasers: OPAL (Lumenis, USA); ACTIVIS (Quantel Medical, France), VISULAS (Zeiss, Germany). Spots of 2, 3, 4, and 5 mm were tested with each laser. Similarly, TTT lasers: OCULIGHT SLx (Iridex, CA) and IRIDIS trade mark (Quantel Medical, France) were evaluated with 2 and 3 mm spot diameter and power ranging from 200 to 1,000 mW. RESULTS: PDT lasers: OPAL had a "top hat" and homogeneous profile whatever the spot size. Numerous micro-spikes and micro-nadirs of power were observed with the ACTIVIS and the VISULAS. TTT lasers: for the IRIDIS the beam shape was rather gaussian, but the homogeneity was reduced by micro-spikes of power. With the OCULIGHT Slx the beam shape was rather top hat and only few micro-spikes or micro-nadirs of power could be disclosed. DISCUSSION: The literature tends to prove that the shape and homogeneity of the beam profile could play a role on the efficacy of the treatment. CONCLUSION: Since PDT and TTT lasers display different beam profiles, this parameter should be carefully evaluated when performing clinical evaluations of PDT or TTT treatments.

Laser Coagulation↗
PubMed2005

Subglottic hemangioma: a comparison of CO2 laser, Neodym-Yag laser, and tracheostomy.

For airway obstruction caused by subglottic hemangiomas, tracheostomy is still regarded by some as the only established therapy, despite numerous other therapeutic options. Resection with lasers was also reported, but subglottic scar formation may occur, and different laser types may have advantages over others. The charts of 46 consecutive patients over 26 years were reviewed. Until 1986, therapy involved systemic steroids or tracheostomy. Thereafter, a Neodym-Yag and after 1995 a CO2 laser was used. Mean initial stenosis was 61.0% in the first (n=15), 85.8% in the Neodym-Yag (n=14), and 86.7% in the CO2 period (n=17). Tracheostomy rates could be reduced from 76.9% to 46.9% with the Neodym-Yag and to 30.8% with the CO2 laser, and to 22.2% in children not intubated before referral. One tracheostomy obstruction resulted in severe neurological damage; granulomas required resection in 37.5%. Secondary subglottic stenosis was found in 15.4% with the Neodym-Yag, but not with the CO2 laser. With tracheostomy, 12.5% were symptom-free at age 2-3 years, vs. 25.0% in the Neodym-Yag and 41.6% in the CO2 laser period. Speech development was delayed in 75.0% with tracheostomy, and parental anxiety lessened in only 18.8% before the second birthday (68.8% without tracheostomy). Since the end of the retrospective analysis, we treated a further 21 patients (mean stenosis, 83.3%) with the CO2 laser, with only one tracheostomy (4.8%). Compared to steroids and tracheostomy, a significant reduction in morbidity and speech developmental delay, and an improved quality of life, were achieved with CO2 laser resection, and this approach was superior to the Neodym-Yag laser.

Anxiety↗
PubMed1978

[Laser lesions of the anterior segment of the rabbit eye. Studies of cornea, iris, lens and sclera using an argon, ruby and YAG-laser].

The anterior segment of the eye of 100 rabbits was exposed to radiation from Argon, Ruby and YAG lasers. The healing process of liminal and supraliminal lesions was evaluated histologically. The iris is the most sensitive tissue for all three lasers (threshold radiant exposure, Argon: 0.004 kJ/cm2, Ruby: 0.01 kJ/cm2, YAG: 0.05 kJ/cm2). Higher energies necessary for lesions in the transparent media were available only with the Argon and YAG lasers. The Argon laser failed to produce lesions in the lens, and threshold radiant exposure for the central cornea was 8 kJ/cm2. The thresholds for YAG lasers lesions in the central cornea and lens were of the same magnitude. The marked absorption of energy by the iris may lead to an accumulation of heat, resulting in lesions of adjacent tissues or a reduction of threshold for those lesions: The threshold in the peripheral cornea was ten times lower than in the center with the Argon laser, four times lower for the YAG laser. The thresholds for Argon and YAG laser lesions in the peripheral sclera lay between the thresholds for the iris and for the peripheral cornea. A safety standard for the anterior segment of the eye should be based on the lowest threshold (Argon laser lesion of the iris). The application of a factor 100 results in a maximal permissible exposure of 40 mJ/cm2. The influence of the beam diameter could not be evaluated.

Animals↗
PubMed1994

Laser sclerostomy ab interno using continuous wave and pulsed lasers in a rabbit model.

PURPOSE: This experimental study was designed to find an optimal combination of parameters for a gonioscopic ab interno approach to laser sclerostomy. METHODS: Laser sclerostomy ab interno was performed delivering the laser energy via a slit lamp and a gonioscopic contact lens to the iridocorneal angle. The laser energy is required to be well transmitted by the cornea and at the same time to be maximally absorbed by the sclera at the iridocorneal angle. For local enhancement of absorption the sclera was stained with the biocompatible dyes Fluorescein (absorption maximum at 480 nm) and Methylene blue (absorption maximum at 668 nm) applied by iontophoresis. A continuous-wave (cw)-Argon laser and a cw-dye laser produced relatively long pulses (200 ms) at wavelengths matching with these respective maxima. Additionally a pulsed dye laser emitting shorter pulses (2 microseconds) was successively adapted to the wavelengths of the two maxima. In some cases a Q-switched Nd: YAG laser had to be used for perforation of Descemet's membrane. A total of 44 rabbit eyes was treated to compare the results for these four different laser/dye combinations. RESULTS: While no successfull perforation of the sclera could be achieved using the cw-dye laser with scleral staining by Methylene blue, the intraoperative success rate ranged between 59% and 75% for the other three laser/dye combinations. Histological examinations of the eyes on the first postoperative day showed smaller thermal necrosis zones, but more often fibrin reactions when using the shorter pulse length. Although we often found iris adherences to the internal fistula ostium, no major complications were observed. CONCLUSION: Further improvement of intraoperative success rates is needed, before clinical application of the approach can be considered.

Animals↗