Search PubMed⌕ Search

Biomedical subjects

T Seiler

Publications and source records attributed to T Seiler.

At least 127 records · Page 7Linked to original sources
PubMed1989

[Visual evoked cortical potentials modified by a NMR magnetic field of 0.24 Tesla].

The visual evoked cortical potentials (VECP) of ten persons with normal vision were investigated under the influence of a nuclear magnetic resonance (NMR) field with a magnetic field strength of 0.24 T. An increase in latency of 2.09 ms for the mean value was found with weak significance and a significant increase of 2.55 ms for the median under magnetic field influence. There were no remaining changes in the VECP after ceasing the magnetic field. The method and results are demonstrated and discussed.

Adult↗
PubMed1989

[Removal of hard tooth substance with Excimer lasers].

The usefulness of an Excimer laser (wavelength 308 nm) to remove enamel and dentin was assessed by examining the necessary energy flow density, micromorphological changes, and irradiated surfaces. Our results demonstrated that it is possible to remove dentin and enamel with the Excimer laser in controlled fashion. The temperature in the pulp cavity rose as a function of the distance to the site of irradiation (corresp. to distance between temperature measuring probe and irradiated tooth surface) and the duration of exposure and amounted to 3.5 degrees C-18.3 degrees C. Differences in the micromorphology of the surface structures were observed as a function of the material (enamel or dentin) and the duration of irradiation.

Dental Cavity Preparation↗
PubMed1989

[Root canal preparation using Excimer laser beams].

An in vitro investigation of root canal preparation on extracted human teeth by 308 nm Excimer Laser radiation was performed. It could be demonstrated that a secure and effective root canal preparation is possible by Excimer Laser radiation. SEM investigations on axially splitted roots showed root canal walls free of smear layer or any other soiling. The dentin-tubuli where open and free of clogging. There was no case of via falsa or overinstrumentation.

Evaluation Studies as Topic↗
PubMed1989

[Magnetic resonance tomography in ophthalmologic diagnosis].

First introduced into clinical use in 1981 as an investigative modality, this technique offers a wealth of information about the topography and physicochemical composition of the soft tissues in the orbit and central nervous system. However, to date, some of this information is still not incompletely understood. This method can be used to augment the usual diagnosis methods in selected cases of intraocular tumor. It is possible to differente between Coats disease and non-calcified retinoblastoma, and the paramagnetic properties of melanin allow the melanin content of choroidal tumors to be estimated. However, so far magnetic resonance tomography (MRT) still cannot, be recommended as a routine diagnostic procedure. MRT is of significant help in localizing pathological processes involving the orbital apex. The optic nerve and its surrounding dural sheath can be imaged with consistent reliability as distinctly separate structures. In cases of retrobulbar optic neuritis, the increase in signals by the pathologically involved segments of the optic nerve permits these segments to be differentiated from the adjacent optic nervous tissue that is unaffected. After administration of paramagnetic contrast material, the sinus cavernosus region can be visualized particularly well. Inflammatory and thrombotic processes can be diagnosed better than with the methods previously available. Surgery can be planned more easily in cases of intracranial space-occupying lesions, especially in the region of the chiasmic portion of the optic nerve; thus at present MRT can be viewed as the method of choice in planning the operative treatment of such lesions.

Diagnosis, Differential↗
PubMed1989

[Usefulness of Excimer lasers in dentistry].

In vitro investigation on the influence of 308 nm excimerlaserradiation on extracted human teeth. Depending on the distance of the area of radiation to the pulp the temperaturerise ranged from 3.5 degrees C (6 mm) to 18.2 degrees C (less than 0.5 mm). REM investigations of radiated surfaces indicate a good retention of filling materials. TEM investigations of radiated dental hard tissues demonstrated that there is no structural change of the ultrastructure below the radiated surface.

Dental Restoration, Permanent↗
PubMed1988

Excimer laser keratectomy for correction of astigmatism.

We treated 13 eyes (12 patients) with excimer laser surgery for correction of astigmatism using linear corneal T-excisions. All eyes were followed up for a minimum of three months. We used a newly developed delivery system and special contact masks to deliver the 193-nm excimer light. Astigmatic corrections of up to 4.16 diopters were obtained. The actual corrections corresponded well with the intended values as predicted by a biomechanical theory. The refractive change over time was different than that observed after knife incisions, suggesting different repair mechanisms. An epithelial plug filling the whole T-excision persisted for over one year in all eyes.

Adult↗
PubMed1988

Side effects in excimer corneal surgery. DNA damage as a result of 193 nm excimer laser radiation.

UV radiation is known to cause actinic damage to the DNA. Excimer laser light, possibly used for keratorefractive surgery, should not produce this damage, as the penetration depth is far less than the diameter of a cell. However, photoreactivation experiments with yeast cells show a significant amount of DNA repair after excimer irradiation. The zone of influence of a small slitlike exposure has a diameter of 2 cm. Consequently, the limbus, the critical location of epithelial neoplasia, always lies within the sphere of actinic damage. Radiation damage is induced by secondary radiation rather than by direct interaction.

Cell Line↗
PubMed1988

Side effects in excimer corneal surgery. Corneal thermal gradients.

Thermal loading is a significant side effect during excimer laser surgery of the cornea. The maximal temperature rise, which is dependent on fluence and repetition rate of the radiation, amounts to 20 degrees C in excised corneas and 7.5 degrees C in the in situ cornea. The temperature decreases exponentially with increasing distance from the incision with a half-value distance of 610 +/- 100 micron. Exposure parameters are recommended to avoid temperature rises greater than 11 degrees C.

Animals↗
PubMed1987

[Morphologic studies of the pathogenesis of ligneous conjunctivitis].

The cases of ligneous conjunctivitis published since 1964 are presented in a review of the literature. A total of 84 cases have been described. The predominance of this disease in women is lower than was previously thought. Ligneous conjunctivitis tends to occur more frequently in children. However, it is not a "disease of little girls". Two cases are described in the present paper, including pathomorphological studies. In both cases, neutrophilic granulocytes were studied by electron microscopy. The results are compared with a control case and with corresponding reports in the literature. The number of granules in the neutrophilic granulocytes was significantly reduced in both cases. In one of the cases studied the granules were increased in size. These findings support the hypothesis that ligneous conjunctivitis could be the result of a lowered resistance associated with a disturbance of wound healing.

Biopsy↗
PubMed1987

[Changes in the outflow facility following cyclocryocoagulation in primary glaucoma. A tonographic study].

The tonographic results in the prospective study carried out by the authors showed that there is a two-phase reaction of the aqueous dynamics after cyclocryotherapy. In the first period, 1 to 3 weeks post-operatively, the aqueous flow decreases. Subsequently it recovers and almost reaches preoperative values. In this stage the outflow facility increases remarkably and is thus the main cause of the reduction in intraocular pressure. There is a close correlation between the changes in outflow and the widening of the chamber angle which can be seen by gonioscopy.

Aged↗
PubMed1987

[Theory of the T-incision of the cornea].

T-incisions are used for surgical correction of moderate corneal astigmatism. No theoretical models to explain the curvature changes have yet been described in the literature. This paper describes a biomechanical model intended to facilitate understanding of the effect of corneal flattening. The incisions cause the stress inside the untouched layers of the cornea to increase. Subsequently the strain also increases and so the curvature radius of the meridian perpendicular to the incision also increases. The calculated changes in the refractive power of the cornea are in good agreement with clinical data. The influence of the depth of the incision is explained quantitatively. Secondary parameters, such as the length of the incision and the size of the optical zone, are discussed.

Astigmatism↗
PubMed1987

[Correction of astigmatism with the Excimer laser].

Excimer laser corneal T-excisions for the correction of astigmatism in eight eyes followed up for three months postoperatively revealed an effective change in refraction of up to 4.2 diopters. The effect depends on the depth of the excision. Although the clinical results agree with astigmatism theory predictions from a biomechanical model of the cornea, some features are not explained by the model. The temporal behavior of the changes in refraction subsequent to excimer laser excisions differ from those produced by blade incisions, indicating a different repair mechanism. The keratectomy technique employed did not result in any serious side effects.

Adult↗
PubMed1987

[Magnetic resonance tomography in ophthalmology. I. Choroid melanoma].

The value of magnetic resonance tomography (MRT) for the diagnosis of choroidal melanomas is illustrated with reference to 26 cases. The geometric dimensions of the tumors are in good agreement with findings obtained by ultrasonography. The relaxation time T2 varies between 85 and 120 msec in contrast to 145-210 msec in subretinal hemorrhages and 190-400 msec in secondary retinal detachments. In contrast to A-scan a differential diagnosis is possible even with lesions less than 1.5 mm in prominence. In solutions of melanin the relaxation time T2 decreases with increasing melanin concentration. This leads to an interpretation that the pigment content of the melanoma is responsible for the relatively short relaxation times. Thus, the relaxation time T2 is a useful factor in predicting metastasis.

Choroid↗