Biomedical subjects

T Kauffmann

Publications and source records attributed to T Kauffmann.

4 recordsLinked to original sources

PubMed2000

[Research articles].

Since 1973, Revista Médica de Chile has classified biomedical and clinical prospective research papers in a Section named "Research Articles", while purely clinical and retrospective studies were classified into another Section, named "Clinical Experiences". This distinction seems no longer necessary, because both types of manuscripts are subjected to a uniform external peer-review system and their intrinsic quality is not a distinctive feature. Furthermore, the name of Sections where similar papers are classified by the major general clinical medicine journals is clearly non-uniform. Therefore, "Research Articles" and "Clinical Experiences" will from now on be included into a single Section: "Research Articles".

Periodicals as Topic↗

PubMed1999

[Etiology of corneal opacities after plasminogen activator-induced fibrinolysis of the anterior chamber].

BACKGROUND: After treatment of anterior chamber fibrinous reactions by tissue plasminogen activator (TPA), irreversible corneal opacifications (calcium phosphate) have been observed. To understand the mechanism of these opacifications an animal model was developed. MATERIAL AND METHODS: In rabbits the lens was removed by phacoemulsification. The surgical procedure was completed by an injection of TPA (25 micrograms) into the anterior chamber. In a second group TPA fibrinolysis (25 micrograms) was induced 10 min after injection of autologous blood. In a third group 25 micrograms of TPA was injected into the anterior chamber after circumscribed mechanical lesion of the corneal endothelium. Changes in corneal structure and transparency were determined by biomicroscopy and histopathologic examination. RESULTS: After lensectomy or mechanically induced lesion of the corneal endothelium followed by TPA injection, sharply defined interpalpebral corneal opacifications developed within 3 to 8 days. Histologically, deposits were located in Bowman's membrane and in superficial stromal layers. No opacifications developed after fibrinolysis of an intracameral clot. CONCLUSIONS: Corneal opacifications as seen in humans after fibrinolysis by intracameral injection of TPA requires a temporary disturbance of the endothelial function. This allows phosphate (buffer of TPA) and calcium (aqueous humour) to distribute within the corneal stroma. Then there are insoluble calcium phosphate precipitates because of recovery of the endothelial function and dehydration of the cornea.

Animals↗

PubMed1996

Corneal reinnervation after photorefractive keratectomy and laser in situ keratomileusis: an in vivo study with a confocal videomicroscope.

The purpose of this study was to compare the regeneration of corneal nerves after photorefractive keratectomy (PRK) versus laser in situ keratomileusis (LASIK) in vivo with a confocal videomicroscope. In all, 15 eyes that had undergone PRK and 15 eyes that had been subjected to LASIK were compared with a confocal in vivo slit-scanning video-microscope. The subepithelial nerves were observed preoperatively and at 3, 6, and 12 months postoperatively. In all eyes, good microscope images of the subepithelial nerve plexus could be obtained preoperatively. Because of postoperative light reflection and scattering in the treated area, subepithelial nerve-fiber regeneration could be followed satisfactorily only in seven eyes after PRK and in five eyes following LASIK. In the eyes treated with PRK, recovery of subepithelial reinnervation started from the margin of the ablation zone, being directed toward the center of the cornea. At 8 weeks postoperatively, rarefied subepithelial nerve fibers were visible at the edges, and after 3 months, single nonbranched nerve fibers could be visualized in the center of the ablation zone. At 6-8 months following PRK, subepithelial nerve regeneration seemed to be completed; however, abnormal branching and accessory thin nerve fibers were present without exception. After LASIK, corneal nerve-fiber regeneration followed the same course described for PRK except that regenerated subepithelial nerve fibers were barely visible in the center after 6 months. Further changes in nerve structure were visible for up to 12 months postoperatively. Recovery of corneal sensitivity in humans has been reported to start at 4-6 weeks after PRK and is said to be completed within 6-12 months of surgery. Slit-scanning videomicroscope findings were in accordance with these observations.

Cornea↗

PubMed1995

[Aniseikonia reduces binocular summation in the VECP].

The binocular summation effect of human VECP (increase in amplitude from about 4.0 microV to about 5.4 microV) was proved and optimized in 32 subjects. Stimulus parameters: TV steady-state pattern reversal (7.0 Hz); pattern size 1 degree; stimulus contrast 5% (higher stimulus contrasts reduced considerably the selectivity of the binocular summation effect); 96 sweeps averaging (Nicolet Compaq Four); position of electrodes: 10% and 30% above Protuberantia occipitalis externa of nasioninion distance. Aniseikonia of 7 to 52% was generated by means of small Galilei telescopes. Because of comparatively large interindividual variance within the series of subjects, no decrease in binocular VECP amplitude could be demonstrated at an aniseikonia less than 52%. On one woman subject, a significant reduction in amplitude (5% level) at 14%, 26% and 52% aniseikonia was apparent, but not at 7%. Thus, for this subject, it was possible to correlate the results with the clinically known limits of toleration for aniseikonia. This result was confirmed by more than 60% of the subjects in the test group.

Adult↗