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At least 721 records · Page 40Linked to original sources

PubMed1990

[Diabetic retinopathy].

The risk of blindness in diabetes may be significantly reduced by a suitable ophthalmic therapy. In order to apply this therapy in due time to the population at risk, all diabetics should be referred to ophthalmological follow-up examination at regular intervals. A rapid progression of a retinopathy may occur in young patients, especially during puberty and pregnancy, after change from oral antidiabetics to insulin and, temporarily, following strict control of blood glucose. Besides normoglycemia, the prevention of a high blood pressure is an important prerequisite of an efficient treatment of diabetic retinopathy. Retinal photocoagulation has been proven the most effective mode of therapy. The correct indication and stage-depending dosage of retinal laser coagulation in diabetes is a demanding task which should be reserved to well-trained specialists in this field. Diabetic vitreous bleeding and retinal traction detachment are complications of advanced proliferative diabetic retinopathy, which can be treated successfully in 60-70% of the cases by modern techniques of vitreoretinal surgery.

Blood Glucose↗

PubMed1982

[Coagulation technic in diabetic maculopathy].

One hundred thirty-six eyes with diabetic maculopathy, which had been operated on by photocoagulation between 1976 and 1980, were followed up with regard to the morphology of the retinal changes and compared with 246 untreated eyes. Of the treated eyes, 77% showed no further progression of the microangiopathy, whereas in 80% of the untreated eyes the development of a diabetic maculopathy was observed.

Adult↗

PubMed1990

[Diagnostic and therapeutic thoracoscopy in spontaneous and traumatic pneumothorax].

224 thoracoscopies were performed to patients with spontaneous and traumatic pneumothorax. Curative thoracoscopy (diathermocoagulation, laser coagulation) was performed in 93 patients, in 42 patients medical glues were used. Out of 93 patients who had been subjected to curative thoracotomy endoscopic operations gave no effect in 5 patients only. Complications after thoracoscopy were noted in 4 patients (2 patients had exudative pleurisy, 2 patients had subcutaneous emphysema).

Adolescent↗

PubMed1990

Nd:YAG coagulation of the verumontanum: an endoscopic attempt at sterilization.

In order to develop a new and less invasive method of sterilization in men we performed photocoagulation of the verumontanum in 10 rams, using a Nd:YAG laser, wavelength 1,060 nm. Under general anesthesia a perineal urethro-cutaneous fistula was achieved, and, by means of a 16F laser-endoscope, transurethral coagulation of the ejaculatory ducts, located in the verumontanum, was carried out, using pulses of 1.5 sec in duration and 20-30 W in power. The animals were killed at different postoperative time intervals, ranging from 1 day to 8 weeks. Injection of methylene-blue into the testicular ducts of the resected prostate-bladder specimen and histologic studies of the coagulated tissue revealed that complete bilateral occlusion of the ejaculatory ducts had been achieved in 4 rams. Failures were due to over-extended irradiation of the verumontanum. Except for urinary tract infections occurring in 4 animals, no serious complications were encountered. Further investigations are still necessary to determine the role of lasers in male sterilization.

Animals↗

PubMed1990

Retinal laser lenses: magnification, spot size, and field of view.

Proper use of ophthalmoscopic contact lenses for retinal photocoagulation requires knowledge of their comparative magnification, spot size, and field of view. We determined these parameters for four commonly used lenses, using data measured from optical components of the lenses and a commonly used photo-coagulator slit-lamp and spot size changer. A Krieger lens has 8% more working field of view and 29% less magnification than a Goldmann lens. A Panfundoscope lens has 84% more working field of view and 24% less magnification than a Goldmann lens. A Mainster lens has 58% more working field of view and 3% more magnification than a Goldmann lens. For Goldmann, Krieger, Panfundoscope, and Mainster lenses, respectively, retinal spot size is 8%, 53%, 41%, and 5% greater than photo-coagulator spot size settings. The field of view of each lens is increased in myopic and decreased in hyperopic patients. Anterior segment irradiance is higher than retinal irradiance for 1000 microns spot size settings with a Panfundoscope or Mainster lens, and this setting should be avoided, especially in patients with hazy ocular media.

Contact Lenses↗

PubMed1992

[Histopathology of retinochoroidal adhesions of diode laser endophotocoagulation lesions in monkey eyes].

Retinochoroidal coagulation effect of 810 nm diode laser was studied using monkey eyes to determine the energy necessary to produce retinochoroidal adhesion safely. Power settings were at 100, 200 and 300 mW. The lesions produced with a power of 100 mW were faint grayish spots. One month after photocoagulation, there was degeneration from the outer granular layer to the superficial choroidal layer. However, chorioretinal adhesion was not obtained due to external limiting membrane formation. The lesions produced with a power of 200 mW were characterized by small whitish spots surrounded by grayish rings and retinochoroidal adhesions were produced by proliferated cells. However choroid were intensely coagulated, and there was a rupture of Bruch's membrane in one lesion. The lesions produced with a power of 300 mW were intense white spots surrounded by grayish rings. Histologically, severe cell loss of the retina was seen and three was no retinochoroidal adhesion. It can be said that it is difficult for 810 nm diode laser to obtain adequate retinochoroidal adhesion safely.

Animals↗

PubMed1976

[Occurrence of diffusions shown by fluorescence angiography of the laser coagulation in animals (author's transl)].

Laser treated rat fundi were observed angiographically and with the fluorescence microscope for 3 months. Angiographically diffusions have been observable up to about one week post laser, fluorescence microscopically, however, for the whole observation time of 3 months. From the 2nd week, these diffusions were produced mainly by neovascularizations which angiographically were not visible. They started from the choroid and penetrated into the outer part of the retina.

Animals↗

PubMed1989

[Long-term results of the treatment of Coats disease].

Fluorescein angiographies and clinical data of 265 patients (292 eyes) with primary retinal teleangiectasis were retrospectively evaluated. If patients showed the typical pathology of the fundus and were less than or equal to 20 years, they were summarized under the diagnosis Coats' disease (125 eyes). These patients revealed significantly more severe vascular changes and exudates compared with older patients with retinal teleangiectasis. The treated and untreated course was compared in the group of patients with Coats' disease. Coagulation treatment and in some cases additional retina detachment surgery resulted in a significantly better course of the disease in contrast to the untreated group. The degree of the pathology of the fundus was the main factor for successful therapy. If the vascular changes regressed, the situation was stabilized for the following years.

Adolescent↗

PubMed1976

Treatment of Coats' disease with photocoagulation.

71 eyes with Coats' disease were treated with photocoagulation. By coagulation of the abnormal vessels the disease process could be halted in 64 eyes over a mean observation time of 2 years and 3 months after completion of treatment. In 51 of these eyes the lipoid deposits regressed. In only 7 eyes a progression of the disease could not be prevented. Complications of photocoagulation treatment were not observed.

Follow-Up Studies↗

PubMed1992

[Changes in the visual field after laser coagulation in type I diabetics].

The authors examined 41 eyes of 22 compensated type I diabetics 1 - 2 years after laser photocoagulation, using an automatic static perimeter Peritest. One fifth of the investigated patients had marked changes - DR20. The patients are not aware of the diminution of the visual field. Even the most extensive diminution of the visual field in this group did not restrict the ability to drive motor vehicles.

Adult↗

PubMed1998

Argon-enhanced coagulation units.

Below, we present our inspection and preventive maintenance (IPM) procedure for argon-enhanced coagulation units. This new procedure follows the format and numbering system used in the Health Devices IPM System. This procedure is intended for use with the Universal Inspection Form (Form 300-0595), which can be found in the published version of the IPM System, or with a custom checklist generated for this procedure by the IPM Task Manager software provided with the IPM System.

Argon↗

PubMed1993

Corneal light scattering and visual performance in myopic individuals with spectacles, contact lenses, or excimer laser photorefractive keratectomy.

Corneal transparency and visual performance are currently receiving much attention after excimer laser surgery. To date, emphasis has been on comparison of eyes on which laser surgery has been performed to eyes with emmetropia. A more appropriate comparison should be between eyes on which laser surgery has been performed and eyes with other forms of correction for myopia. Forward-scattered light, back-scattered light, and visual acuity were investigated and data were collected from 35 myopic individuals with various types of correction for myopia (spectacles, hard and soft contact lenses, and excimer laser surgery). Forward-scattered light was measured by using a new computerized technique, back-scattered light was measured with a charge coupled device-camera system, and visual acuity was measured with a computerized system at various levels of contrast. Spectacles, hard contact lenses, and excimer laser surgery are all superior to soft contact lenses in terms of light scatter and low-contrast visual acuity and excimer laser photorefractive keratectomy produces comparable results to spectacles one year postoperatively. At low-contrast visual acuity, mean visual acuity was 2.45 minutes of arc for the spectacle wearers, 3.21 minutes of arc for the hard contact-lens wearers, and 5.04 minutes of arc for the soft contact-lens wearers. Excimer laser patients had a mean visual acuity of 9.04 minutes of arc three months postoperatively, and 2.53 minutes of arc after one year. A mean value of 2.4% contrast for forward light scatter was obtained for spectacle wearers compared with a level of 3.84% contrast for hard contact-lens wearers and 16.1% contrast for soft contact-lens wearers. The mean value for excimer laser patients was 20% contrast three months postoperatively and 2.1% contrast one year postoperatively.

Contact Lenses↗

PubMed1990

[Laser microsurgery in the sequelae of an inflammatory reaction of the uveal tract to IOL implantation].

Argon laser (intensity--0.4-0.6, exposition--0.1-0.2 seconds, spot diameter--100-150 mm, the angle to the optic axis of the eye--45-50 degrees) was used for coagulation of precipitates on the anterior and posterior surfaces of intraocular lenses made of polymethyl methacrylate. Laser radiation, 1-2 sessions, was used in 40 patients with precipitates in the optic centre of intraocular lenses, 1-6 months after intraocular correction. Remote observations, within 3 years, have shown rise of visual acuity in the postoperative period. No complications were recorded.

Adult↗

PubMed1988

Deep localized neodymium (Nd)-YAG laser photocoagulation in liver using a new water cooled and echoguided handpiece.

Thirty-six deep hepatic lesions of localized photocoagulation were induced in 11 pigs by means of a neodymium-YAG laser. Laser applications of 80 W/10 sec (10.190 W/cm2) were transmitted through a handpiece coupled to a water-cooling circulation system to protect the quartz fiber and positioned through an echo-guided trocar. During irradiation, temperature was sufficient for vaporization up to 5 mm from the laser source and high enough for tumor cell kill at a 10-mm distance (54 degrees C/60 sec). Intraoperative ultrasound visualized increasing photocoagulation (12-18 mm), and further controls demonstrated an echo-free core of vaporization progressively covered by increasing fibrosis, well demarcated from normal parenchyma. Microscopy revealed central coagulative necrosis marginated from the third day by a growing fibrosis. By day 20 immunoblasts and mast cells were in profusion in the lesion border, and by day 120 a fibrotic network had invaded the scar and confirmed healing free of complication. This technique is proposed for deep vaporization of disseminated hepatic metastases.

Animals↗

PubMed1987

Percutaneous transluminal coronary angioplasty restenosis: potential prevention with laser balloon angioplasty.

Restenosis after percutaneous transluminal coronary angioplasty may result primarily from the combination of a thrombogenic surface and local flow separation produced by disruption of the arterial wall and lumen. Elastic recoil and, perhaps, cellular proliferation further contribute to luminal compromise after percutaneous transluminal coronary angioplasty. Laser balloon angioplasty, performed during the final inflation of an otherwise conventional balloon angioplasty procedure, uses the coagulative properties of Nd:YAG laser radiation to weld together disrupted tissue elements thermally, to reduce elastic recoil and to destroy viable arterial tissue. Studies in human postmortem atheromatous arteries and in animal models in vivo indicate that laser balloon angioplasty, by creating a lumen that approximates the size and smooth cylindrical shape of the balloon, should be effective in the treatment of important causes of restenosis.

Angioplasty, Balloon↗

PubMed1987

Comparative investigations of the effects of the neodymium:YAG laser at 1.06 microns and 1.32 microns on tissue.

The beneficial deep homogeneous coagulation of neodymium (Nd):YAG laser radiation at 1.06 microns owing to low absorption and high scattering in tissue has been documented widely. For another Nd:YAG laser wavelength at 1.32 microns the absorption coefficient of water and saline is approximately ten times higher than at 1.06 microns. This results in more efficient energy conversion into heat in tissue at 1.32 microns. The extinction coefficient in blood at 1.32 microns is only one-third of that at 1.06 microns. We would expect this to result in less heat dissipation by blood and deeper penetration in tissue at 1.32 microns. Nevertheless, at this wavelength scattering also contributes to an effective, uniform distribution of the laser light in the tissue. Animal experiments have been done to examine the effect of wavelength, irradiation time, and beam geometry on tissue damage and to assess its possible clinical uses. The results imply that the 1.32 microns wavelength will produce further indications for the use of the Nd:YAG laser in surgery.

Animals↗

PubMed1991

Dye laser photocoagulation through experimentally induced retinal hemorrhage.

The histological effects of photocoagulation obtained by using each of 4 wavelengths of the dye laser (577, 590, 610, and 630 nm) on experimentally induced retinal hemorrhage in cat eyes were examined. Energy from 577, 590, and 610 nm laser was directly absorbed by red blood cells in the retinal hemorrhage and destroyed the inner layers of the retina. Red blood cells were not directly coagulated with the use of 630 nm laser, and the retinal pigment epithelial cells (RPE cells) and choroidal melanocytes were coagulated. These results suggest that the use of yellow or orange dye lasers for photocoagulative therapy in a retinal hemorrhage is dangerous, because of the risk for destruction of the inner layers of the retina. A 630 nm dye laser is useful for photocoagulation of a retinal hemorrhage, while the laser energy is unable to reach the RPE cells and the choroid with the use of other wavelengths.

Animals↗

PubMed2002

Optical properties of selected native and coagulated human brain tissues in vitro in the visible and near infrared spectral range.

Medical laser applications require knowledge about the optical properties of target tissue. In this study, the optical properties of selected native and coagulated human brain structures were determined in vitro in the spectral range between 360 and 1100 nm. The tissues investigated included white brain matter, grey brain matter, cerebellum and brainstem tissues (pons, thalamus). In addition, the optical properties of two human tumours (meningioma, astrocytoma WHO grade II) were determined. Diffuse reflectance, total transmittance and collimated transmittance of the samples were measured using an integrating-sphere technique. From these experimental data, the absorption coefficients, the scattering coefficients and the anisotropy factors of the samples were determined employing an inverse Monte Carlo technique. The tissues investigated differed from each other predominantly in their scattering properties. Thermal coagulation reduced the optical penetration depth substantially. The highest penetration depths for all tissues investigated were found in the wavelength range between 1000 and 1100 nm. A comparison with data from the literature revealed the importance of the employed tissue preparation technique and the impact of the theoretical model used to extract the optical coefficients from the measured quantities.

Brain↗