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At least 1,117 records · Page 62Linked to original sources
PubMed1989

[Laser treatment of macular subretinal neovascularization in angioid streaks].

The authors examined 17 eyes with macular subretinal neovascularization in angioid streaks treated by direct laser photocoagulation. Two eyes were treated with dye laser (590 nm), two with blue-green argon, three with green argon and ten with red krypton laser. At twelve-month follow-up, the visual acuity was of 0.21, a statistically significant decrease respect to the presenting vision. Poor functional results are due to the frequent recurrences of neovascularization.

Adult↗
PubMed1989

[Senile macular degeneration: surgical management and histopathologic features].

Choroidal neovascularization often complicates senile macular degeneration; argon and krypton laser photocoagulation are very useful to stop visual acuity decrease caused by extrafoveal choroidal neovascular membrane (NVM) in a large group of patients. Unfortunately, in a large number of cases, NVM causes haemorrhagic serous detachment, disciform scar and, sometimes, vitreous hemorrhage. In these patients it is impossible to perform laser treatment. A three ports pars-plana vitrectomy has been performed for the treatment of intravitreal hemorrhage in a case of haemorrhagic disciform lesion and in two cases of extensive subretinal haemorrhage secondary to subretinal NVMs. Posterior pole focal retinotomies have been created to remove the NVMs in order to prevent further hemorrhages; an internal tamponade has been performed and the retinotomies closed with endophotocoagulation or endocryo. The specimen of the membranes, stained for light microscopy, have been studied. During the months of follow-up (9 months) no subretinal membrane no retinal detachment developed but fibrosis at the retinotomy sites led to traction on the macula. The functional aim of this surgery is limited to the restoration of a clear vitreous and to a reduction in the diameter of the central scotoma in the cases of a recent subretinal haemorrhage.

Aged↗
PubMed1989

[Retinal pigment epithelial tears after photocoagulation in age-related macular degeneration].

Retinal pigment epithelial tears after photocoagulation for subretinal new-vessels complicating age related macular degeneration were observed in 20 patients between 1980 and 1988. The patients, 4 males and 16 females, aged from 60 to 86 years (mean: 72.5) were followed up between 12 and 53 months (mean: 21 months). Laser photocoagulation was performed for directly visible lacy subretinal new-vessels (6 cases) or vascularized pigment epithelial detachment (10 cases) or both lesions associated (4 cases). Krypton laser (17 cases), blue-green argon laser and/or orange dye laser (625 nm) (3 cases) were applied in one (9 cases) to four sessions. Retreatment (11 cases) was performed for persistent subretinal new-vessels (3 cases) or recurrences (4 cases) or appearance of a pigment epithelial detachment after photocoagulation for isolated SRNV (4 cases). The tear was observed on fluorescein angiography 10 to 180 days after the last session. It was preceded by occurrence of subretinal hemorrhages, increase in size of the PED or newly formed PED. It appeared on the border of the PED (16 cases) usually temporally, or on the immediate border of the laser scar (4 cases). Further evolution was rapidly defavorable with dramatic impairment of vision and constitution of fibrovascular scar in the macular area. Only 4 eyes progressed to flat atrophic scars after retreatment and retained useful central vision (0.1 to 0.2). Factors which could explain this complication following laser treatment of age related macular degeneration are discussed.

Aged↗
PubMed1989

[Laser treatment of subretinal macular neovascularization in pathologic myopia].

The authors evaluated retrospectively 100 eyes with pathological myopia and a macular subretinal neovascular membranes (SRNV) which was treated with direct laser photocoagulation. Argon green, krypton red and orange dye (590 nm) laser were used to treat, respectively, 19, 63 and 18 eyes. The follow-up period was of 12 months. Mean initial visual acuity was 0.33 and mean final visual acuity was 0.31, with no statistically significative difference between them. One or more recurrence was observed in 44% of the eyes. Recurrences could be treated in 80% of cases. At the end of the follow-up period SRNV had disappeared in 83 eyes and extended into the foveola in the remaining 17.

Adult↗
PubMed1989

Laser light: its nature and its action on the eye.

Lasers produce a coherent, focused, monochromatic, high-energy form of light. Because laser surgery is more versatile and precise and is freer of complications than conventional surgery it has become widely accepted in ophthalmology over the past 10 years. Applications range from routine procedures in the fundus to recent, more delicate interventions in the cornea. The argon laser is the most widely used to treat extrafoveal chorioretinal diseases such as age-related macular degeneration and diabetic retinopathy; it has also been used successfully to treat glaucoma by iridectomy or trabeculoplasty. The krypton red laser is the argon laser's counterpart in the treatment of subfoveal and pigment-epithelium-related diseases. Posterior capsulotomy is the most widespread and successful intervention with the neodymium:yttrium-aluminum-garnet crystal laser; this laser is also used to cut vitreous traction bands and is increasingly used in iridectomy. Although the use of the excimer laser in corneal surgery is still largely investigational it has been shown to produce precise cuts in corneal layers for the correction of myopia or astigmatism. The variable-wavelength dye laser, capable of reaching a specific level in the retina or choroid, has offered exciting new developments, and it promises to soon be part of the ophthalmologist's armamentarium in the treatment of eye disease.

Eye↗
PubMed1989

[Multifocal choroiditis: diagnostic aspects and results of photocoagulation. Apropos of 25 cases].

A retrospective study was conducted on 25 patients who presented with both recurrent multifocal choroiditis and subretinal neovascularisation. As in other series, striking features were the young age of the patients (mean age 33 years), frequent recurrences of the macular lesions during a limited follow-up period, inflammation of the vitreous or the optic disk, and macular fibrosis. However, unlike previously reported data, refraction was more often in the emetropic range, there was no female predominance, and inflammatory signs were mild or limited to papillitis. Moreover serologic tests did not indicate an acute infection due to Epstein-Barr virus in any of the patients. This study also emphasized the results of Krypton laser treatment of the subretinal neovascularisation. Final visual acuity improved or remain the same in 26 eyes (72%) and worsened in 11 eyes (28%) during a mean follow-up period of 13 months (range 2-48 months). The best results were obtained in 15 eyes with neovascular membranes located more than 200 mu from the foveal avascular zone (mean final visual acuity: 20/40). However the mean final visual acuity of the nine eyes with neovascular membranes closer than 200 mu from the FAZ, was over 20/60. Recurrences of subretinal neovascularisation occurred in 7 out of 24 treated eyes and 3 were under the center of the FAZ. These results should be confirmed by a randomized prospective clinical trial in order to assess the benefits of laser treatment in recurrent multifocal choroiditis.

Adult↗
PubMed1987

[Calculation of the ventilation-perfusion ratio in the scintigraphic diagnosis of pulmonary embolism].

Ventilation perfusion scanning fails to diagnose pulmonary embolism in matched defects. In 61 patients (19 with pulmonary embolism proved by angiography, 32 with chronic obstructive lung disease and 10 with acute bacterial pneumonia) we computed the ventilation perfusion ratio (V/Q) in these matched defects, using Krypton 81 m. This analysis demonstrated that the diagnosis of pulmonary embolism could be made with a specificity of 100% when the V/Q ratio was greater than 1.2 in the matched defects. Pulmonary embolism was characterized by a perfusion defect with a high V/Q ratio, even in Laennec infarction. In contrast, the analysis excluded the diagnosis of pulmonary embolism and suggested another disease when the V/Q was less than 0.95 with a specificity of 95%. Perfusion defects in acute pneumonia always had a V/Q less than 1. The diagnosis remained difficult in chronic obstructive lung disease when pulmonary embolism was suspected on subsegmental defects. Nevertheless this could be solved in about 50% of the cases by quantitative analysis. We feel, therefore, that ventilation perfusion scanning should be quantified by V/Q analysis to improve the diagnosis of pulmonary embolism.

Adult↗
PubMed1986

[Intraarterial DDP and angiotensin II infusion chemotherapy].

Twenty-four patients, each with advanced bladder cancer (BC) or brain tumor (BT), were treated by intraarterial infusion of angiotensin II in combination with DDP as the main drug together with other anticancer drugs. As for the frequency of treatment by the intraarterial therapy, only one course was given in 15 cases, two courses in 9 (BC), one course in 21 cases, and two courses in 3 (BT). CR was obtained in ten of 24 evaluable patients with BC and PR in eleven. Of 20 evaluable patients with BT, 3CRs and 7PRs were attained. The selective enhancement of tumoral blood flow induced by regionally infused angiotensin II was observed using continuous intraarterial infusion of krypton-81 m.

Adolescent↗
PubMed1987

Regional lung function in long-term survivors after chemotherapy for small cell lung cancer.

In order to evaluate the regional lung function in patients with small cell lung cancer with long-term survival, we measured the regional lung function in 17 patients. We studied the patients with 81m-krypton ventilation scans and 99m-technetium perfusion scans, as well as measurements of static lung volumes (VC, RV, TLC), flow volume indices (FEV1, FVC, MEF50), and carbon monoxide diffusing capacity (DLCO). We found both the ventilation and the perfusion of the affected lung to be slightly but significantly lower (P less than 0.05), while no obvious ventilation or perfusion defects could be identified at the former tumor site. The static volumes of the lungs, the FVC and the FEV1 were within predicted normal values, while a significant decrease was seen in the PEF, MEF50, and DLCO. It is concluded that patients with small cell lung cancer who obtain complete remission with normalization of the chest X-ray and long-term survival after 18 months of intensive chemotherapy also have a nearly normal lung function.

Aged↗
PubMed1987

[Measuring coronary circulation using an inert gas method--a comparison of common indicator gases].

Validation studies of inert gas techniques are limited in number and usually have not included circumstances with marked heterogeneity of flow. This study was intended to investigate the validity of the method in experimental animals under various hemodynamic conditions by parallel application of helium, argon, krypton and xenon as indicators and by comparison with direct flow measurements. Gases were applied by single breath inhalation. In order to avoid the limitations of conventional methods arising from the systemic recirculation of tracer and from shortened measuring periods we used continuous mass spectrometric recording and numeric deconvolution of the dilution curves in arterial and coronary venous blood. When the transit times are evaluated by "stochastic" analysis and commonly used tissue/blood partition-coefficients (lambda He = 0.95, lambda Ar = 1.1) the helium and argon values are found in reasonable agreement with reference flows. The effects of a shortening of measurements that are based on single integrated samples (Argon method) are shown under control conditions, adenosin infusion and elevated ventricular filling pressure. With xenon (lambda Xe = 0.7) coronary blood flow above 100 ml/min X 100 g is underestimated by the "stochastic" and by the "initial slope technique"; parallel measurements with argon suggest that in the initial slope technique a lambda Xe between 0.8 and 0.9 might be more adequate.

Animals↗
PubMed1988

Treatment of small choroidal melanomas with photocoagulation.

Seventeen eyes with small choroidal melanomas presumed to be malignant were photocoagulated. The melanomas measured 7 to 15 mm at the tumor base and 2 t0 5 mm thick. First, photocoagulation using the green argon laser was aimed at closing the choroidal vascular supply of the tumor. In a second stage, tumor tissue was destroyed using the red krypton laser for confluent burns of long duration. Such treatment was supplemented by cryotherapy in peripherally located tumors or whenever photocoagulation alone did not result in tumor regression. Photocoagulation alone was used in ten eyes and combined wih cryotherapy in seven. After an average follow-up of 42 months, marked tumor regression was achieved in 12 eyes and some tumor regression in two. Tow eyes ultimately required proton beam irradiation, and one eye was enucleated. No metastasis occurred during follow-up.

Aged↗
PubMed1988

Pseudophakic and aphakic pupillary block.

Fifteen eyes of 14 patients who underwent cataract extraction surgery with or without lens implantation developed pupillary block. Six lenses were of the anterior-chamber type, two of the posterior-chamber, and four of the iris-clip Binkhorst type; three were simple aphakic eyes. Ocular hypertension was present in 12 eyes; while in three eyes, the pupillary block was detected by biomicroscopic examination. In order to relieve the block, we performed one of the following three procedures: laser (yttrium aluminum garnet (YAG), argon, or krypton) iridotomy, YAG laser photodisruption of the anterior vitreous face, or pars plana vitrectomy.

Adolescent↗
PubMed1987

Quantification of regional ventilation in humans using a short-lived radiotracer--theoretical evaluation of the steady-state model.

The accuracy of the steady-state measurement of ventilation by means of a short-lived insoluble inert gas tracer rests with the validity of the steady-state flow equation. This has previously been applied to the qualitative assessment of regional ventilation using krypton-81m, but may potentially be used for the calculation of regional alveolar ventilation per unit alveolar gas volume--(VA/VA)cal--from measurements of the alveolar concentration of the tracer. The steady-state alveolar tracer concentration was calculated for the course of a breathing cycle, using a lung model featuring airways dead space and tidal gas flow. The calculations were made by computer simulations of a lung, characterized by predefined values of parameters describing the lung structure and the mode of ventilation. In the normal lung of supine man at rest (specific alveolar ventilation, ranging from 1.0 to 3.5 min-1) the errors of (VA/VA)cal relative to the predefined true values range from an overestimation by some 3% in the low ventilation regions to an underestimation by 8% in the best ventilated regions. The errors mainly result from ventilation of the airways dead space, which will influence the distribution of tracer in the lung by the transfer of tracer between regions by way of the common dead space and by the decay of tracer during its transport through the bronchial tree.

Humans↗
PubMed1987

A Monte Carlo simulation of Auger cascades.

The energy imparted to biological tissue after the decay of incorporated Auger emitters stems from two sources: (a) energy deposition by the Auger and Coster-Kronig electrons and (b) the charge potential which remains on the multiple ionized atom after the end of the cascade. For the numerical assessment of both the kinetic energy of the released electrons and the charge potential, a new and--for purposes of microdosimetry--precise method is presented. Based on relativistic Dirac-Fock calculations and a rigorous bookkeeping, this method provides a perfect energy balance of the considered atomic system when applied to Monte Carlo simulations of Auger cascades. By comparing the results for charge distribution for krypton and iodine with experimental data and the electron spectrum of 125I with theoretical data, it can be shown that the approach followed in this work is reasonable and appropriate for the determination of the energy deposited by incorporated Auger emitters in small volumes of condensed matter. The total energy deposited by 125I in a volume of 20-nm diameter is 2.03 keV which is made up by multiple ionization (1.07 keV) and energy deposition by the emitted Auger electrons (0.96 keV).

Chemical Phenomena↗
PubMed1986

Regional pancreatic perfusion. An experimental study in the dog.

Blood flow and perfusion in the canine pancreas have been measured in many experimental models but little attention has been directed to perfusion in different regions of the gland. In some preparations "accessory" vessels have been ligated to allow measurement of flow through one vessel and the effect on perfusion of ligating these vessels is unclear. This study has measured pancreatic blood flow by the electromagnetic flow technique and regional perfusion by the clearance of Krypton-85 (85Kr) in three preparations of the pancreas. Results demonstrate no difference in perfusion between different regions if all vessels are intact. However, following accessory vessel ligation, the tail and part of the body of the gland become macroscopically ischaemic and perfusion in the uncinate process is reduced. This problem was overcome when the head of the gland was isolated as the measurements of both arterial blood flow and perfusion were almost identical; it is therefore the preferred preparation of the gland for measuring blood flow and perfusion.

Animals↗
PubMed1985

Carbon dioxide laser in ophthalmic plastic and orbital surgery.

The CO2 laser cuts tissue by flash boiling extracellular or intracellular water molecules in contact with the beam. This vaporization sterilizes the tissue and seals capillaries. The CO2 laser seems most useful in ophthalmology to vaporize lymphangiomas and capillary hemangiomas and to provide hemostasis in patients with bleeding disorders. The cutting beam of the CO2 laser can be attached to the operating microscope to facilitate surgery deep within the orbit. The effectiveness of the CO2 cutting action depends upon water content of the tissue rather than tissue color as with argon and krypton lasers. Skin incisions show less scarring when made with conventional scalpel, but more precise surface cutting lasers may allow more precise microsurgical excision of eyelid tumors than can now be accomplished with a scalpel.

Eye Diseases↗
PubMed1979

Red fluorescence in older and brunescent human lenses.

Brunescent lenses and normal human lenses more than 70 years old exhibit red fluorescence due to a fluorophor with emission maximum at 672 nm under excitation by the 647.1 nm line of krypton ion laser. The properties and mode of occurrence of this fluorophor suggest that its formation is highly pertinent to senile nuclear pathology.

Adolescent↗
PubMed1979

The importance of an elevated skin temperature in transcutaneous oxygen tension measurement.

The oxygen tension as measured by a heated transcutaneous polarographic electrode has been shown by a number of workers to correlate closely with the arterial blood oxygen tension as measured by accepted invasive methods. The present paper presents a study of the dependence of the measured skin oxygen tension values on the temperature of the sensor. A graph is included that emphasizes that the skin sensor temperature should be greater than 43 degrees C if the device is to be operated in the platequ region. The effect of increasing the skin temperature on both the local blood flow and the associated skin permeability changes has been studied. Skin blood flow studies were performed by means of a radioisotope washout technique using krypton-85 and xenon-133 together with a Huch transcutaneous oxygen electrode. The electrode control system incorporates a heating power monitor that Huch and co-workers suggest can indicate the relative blood flow in the tissues beneath the electrode. Two techniques for localized heating of the skin were employed during the washout experiments. First, a copper tube heating ring supplied from a water bath surrounded the area of measurement. Second, a focused source of light applied heat directly to the area of interest, which was 12 mm in diameter. Information obtained in the course of using a quadrupole mass spectrometer with a heated skin probe has given some information about the permeability of the skin and underlying tissues. In these studies three gases were used. Oxygen and argon are transported by the blood, but carbon dioxide tends to be generated within the tissues, and its skin tension is less affected by the blood content. Between 36 degrees C and 45 degrees C it is possible to relate changes in the oxygen and argon skin tensions to changes in capillary blood flow.

Adult↗