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Biomedical subjects

M U Dardenne

Publications and source records attributed to M U Dardenne.

At least 19 recordsLinked to original sources
PubMed1989

Retrospective study of retinal detachment following neodymium:YAG laser posterior capsulotomy.

A retrospective study of 1,000 cases that had Nd:YAG laser posterior capsulotomy after cataract surgery is presented. We analyzed the correlation of the patient's age, axial length of the eye, method of cataract surgery, and laser parameters (exposures, energy, and burst mode) with the incidence of retinal detachment (1.6% overall). The highest risk for retinal detachment (12.3%) was in patients with an axial eye length of 26.1 mm to 28.0 mm. The average age of patients with retinal detachments was 60.6 years, ten years younger than the collective average age. Laser parameters, such as energy, exposures, and burst mode, and the method of cataract surgery (extracapsular or phacoemulsification) did not correlate with the incidence of retinal detachment. After surgical treatment of the 16 retinal detachments, a good postoperative visual acuity (better than 20/40) was achieved in most cases.

Adolescent↗
PubMed1989

[Preparation of hard tooth structure with Excimer lasers. In vitro study].

The present study will show, that caries removal and conditioning of tooth surfaces by an (ArF)*-Excimer-Laser is an alternative to conventional preparation methods without thermal and mechanical irritations. This promises caries removal without pain to the patient. The photoablative process leads to retentive surfaces of the treated cavities. These findings promise good results in adhesive techniques. In vitro studies show, that photoablation of dental tissue is effective enough to make clinical usage possible.

Dental Caries↗
PubMed1989

[Preparation of hard tooth structure with Excimer lasers].

In this study the possible application of photoablation with an Excimer UV laser for the creation of retentive surfaces was studied as an alternative to conventional enamel conditioning methods using acids. Surfaces of untreated enamel and of prepared cavities were irradiated with an argon fluoride Excimer laser at a wavelength of 193nm and evaluated in a scanning electron microscope. The bond strength of composites to these surfaces was measured in tear tests. "Laser conditioning" left the surfaces similarly roughened as chemical etching. The variable extension of the laser field allows a sharp delineation of the area to be conditioned. The tear tests with human tooth enamel showed bond strength values corresponding to approx. 75% of those obtained by acid etching techniques. The question if these bonds are durable is the subject of current studies.

Adhesiveness↗
PubMed1988

Mass spectroscopic analysis of excimer laser ablated material from human corneal tissue.

The clinical feasibility of photorefractive keratectomy depends on the surface structure of the ablated cornea. Two factors that influence the remodeled surface are the homogeneity of the energy distribution and the properties of the laser source (energy and wavelength). Currently, the homogeneity of the beam is difficult to control. The second factor, laser source properties, was the focus of this study. We investigated the effect of laser wavelength and energy by analyzing the reaction products of photoablation. We monitored the fragments produced by UV-laser ablation of human corneas using mass spectroscopy in the range of 0 to 100 atomic mass units. At 248 nm (KrF), average photon energy was 5 mJ/cm2, increased to 90 mJ/cm2 by intervals of 5 mJ/cm2. At 193 nm (ArF), photon energy was increased by the same interval from 5 mJ/cm2 to 80 mJ/cm2. Our experiments showed that there was a fluence threshold of approximately 40 mJ/cm2 at 193 nm (ArF) and 50 mJ/cm2 at 248 nm (KrF). Exceeding this threshold led to sudden increases in the number and relative intensity of fragment peaks in mass spectroscopy. This indicates the onset of multiple-photon processes and effective photochemical breakdown. There was a significant difference between both wavelengths in the distribution of mass peaks, indicating higher ionization power at 193 nm.

Adult↗
PubMed1985

[Initial experiences in the treatment of changes in the anterior eye segment with the neodymium:YAG laser].

The present paper reports the first results with the Meditec OPL-3 neodymium:YAG laser (Rodenstock, Munich). The YAG laser is a pulsed laser, the biological effects of which are based on the formation of plasma at its focal point. Plasma formation induces a rapid explosion-like expansion of the tissue. This effect can be used to sever opaque structures of the refractive media of the eye, such as secondary cataracts, membranes or strands. The paper summarizes the results of the first 80 consecutive cases treated with the laser. The surgical procedure is described in detail. Visual acuity improved instantaneously in all cases in which no concomitant eye pathology (e.g., corneal or macular changes) existed. Complications consisted in the development of postoperative inflammatory reactions and increases in intraocular pressure, and responded well to corticosteroids and beta-blockers or Diamox. The development of the neodymium:YAG laser has considerably advanced our therapeutic possibilities.

Aged↗
PubMed1982

[Experiences with the 1st 1400 posterior chamber lens implantations after phacoemulsification].

Since May 1979 the authors have performed 3000 posterior chamber lens implantations; the purpose of this report is to present interim data on the first 1400 cases. The mean age of the patient was 69 years; lens power was determined biometrically, and the diopter range of the implant lenses was between 10 and 30 D. Postoperatively 93.7% of the patients had a visual acuity of 0.5 or better, 70% between 0.8 and 1.0. Serious complications, such as corneal edema, lens luxation and expulsive choroidal hemorrhage have not occurred so far; slight complications such as decentration of the lens, secondary, glaucoma and synechiae have seldom been observed and have reacted favorably to therapy.

Aged↗
PubMed1976

[Ektomia of the anterior lens capsule in extra-capsular cataract operations (author's transl)].

A technic is described to show how to excise the anterior part of the capsule of the lens without defluction of the aqueous humor, in order to make possible a complete irrigation and aspiration of the equatorial lens material by extracapsular cataractsurgery especially by Lens Aspiration and by Kelman Phakoemulsifikation (KPE). By this the resorption of possible lens remains is revealed. Later turbidity of the posterial capsule by remains of the anterior capsule, coming into contact with the posterior capsule are prevented. This excision of the anterior capsule makes easier dislocation of the nucleus of the lens into the anterior chamber which is necessary for KPE.

Anterior Chamber↗