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Biomedical subjects

B Jean

Publications and source records attributed to B Jean.

At least 37 records · Page 2Linked to original sources
PubMed1990

[Laser scanning in ophthalmology].

The current state of the art for the major laser scanning methods, laser scanning ophthalmoscopy (LSO) and laser tomographic scanning (LTS) is discussed and the function principles are described. Experience with a prototype of each instrument from Rodenstock (LSO) and Heidelberg Instruments (LTS) is reported. LSO imaging of the cornea, vitreous, retina, and optic disc, as well as on-line processing is demonstrated with examples (nerve fibre colour coding and histograms). Measurement of the cornea, optic disc and retinal topography with LTS is also demonstrated with examples. An example of polarization optical imaging of the cornea's assumed interferometric "tension patterns" is shown. The current status and future possibilities of laser scanning, its expanded diagnostic potential with microperimetry, IR scanning angiography and polarization optic imaging and measurement (eg. nerve fibre thickness) is discussed extensively. The safety aspects of laser light exposure of the macula are also mentioned. Laser scanners as imaging and measuring sensors of unknown accuracy open a new area of possibly revolutionary diagnostic possibilities.

Cornea↗
PubMed1990

[Imaging the optic papilla with the laser scanning ophthalmoscope].

The laser scanning ophthalmoscope offers tissue examination and support of papillometrical evaluations as a result of different forms of illumination. Confocal, mixed, and Tyndall light are used in the differential diagnosis and identification of the scleral rim. With highpower mixed light under miotic conditions, imaging of the excavation is possible.

Glaucoma↗
PubMed1989

[Use and technic of the CO2 laser on the external surface of the eye].

The CO2 laser, emitting at 10,600 nm in the extreme infrared wavelength has special advantages for ophthalmology: its hemostatic properties and its ability to cut, vaporize, and shrink tissue make it particularly effective on the external eye and adenexae. In particular, it can be used for layerwise removal of tissue on the conjunctiva, the sclera, and the lids. Energy and exposure time are especially important. Irradiation of sclera from enucleated globes showed that these two parameters have a direct effect on the depth of craters - the CO2 laser's typical impact - and the laser's thermal effect on tissue. Technical and practical observations and the clinical results of more than 80 cases treated with the CO2 laser are presented and discussed. The low-power CO2 laser is a useful ophthalmological tool which can partially replace conventional surgery and extend treatment indications.

Conjunctival Diseases↗
PubMed1989

[CO2 laser vaporization of xanthelasmas].

Until now surgery was the only means of removing xanthelasmas. However, their proximity to blood vessels and consequent tendency to bleed makes visual supervision of the excision difficult. The CO2 laser's infrared wavelength permits photovaporization of tissue with excellent hemostasis. It is thus an ideal tool for removing xanthelasmas. Visual supervision is excellent, and the laser's shallow penetration depth permits layerwise removal of the yellow foam cell plaques. The resulting lesions heal without significant scarring, and deeper layers of the skin remain unharmed. The procedure is fast and easy, and postoperative care is minimal; cosmetic results and patient acceptance are excellent. A clinical case and the results of ten treatments are described. The authors conclude that surgical excision of xanthelasmas can be replaced entirely by CO2 photovaporization.

Adult↗
PubMed1989

[CO2 laser vaporization of papilloma of the conjunctiva and eyelids].

In irradiated tissue, the farinfrared CO2 laser generates high temperatures of around 400 degrees C. Thermal damage can occur at the borders of the area being treated, but there are good hemostatic properties and thermal sterilization of the irradiated tissue. Photovaporization of papillomas has been occasionally proposed to achieve thermal inactivation of papilloma viruses and reduce the recurrence rates. Seventy-five cases of recurrent squamous papilloma were vaporized with a CO2 laser and followed-up for over 2 years. Only 2 recurrences were observed (20% have been reported after surgical excision). The procedure is quick, safe, easy to perform and well accepted by the patient. Good hemostatic properties, lack of cicatrication, and excellent cosmetic results are further advantages. Histological examination may be limited by thermal tissue damage.

Adult↗
PubMed1987

[A tracker for ophthalmology].

Real-time tracking of eye movements offers a solution to various problems in ophthalmology. Different types of image analysis and processing techniques is discussed and an advanced pattern recognition eye-tracking system has been developed; it can track a retinal target (in real time) under conditions typical for ophthalmologic examination and therapy. The sensor is a modified low-light video fundus camera. An example illustrates how a retinal target is automatically found again when it has been "lost".

Eye Movements↗
PubMed1987

[Malaria tropica with macular hemorrhage].

We describe the case of a 33-year-old patient with recurrent tropical malaria, comma and isolated subpigmentepithelial macular hemorrhage causing irreversible visual loss. This strictly subpigmentepithelial macular hemorrhage is the second case described. Its importance lies in the fact that the typical plugging of vessels in acute tropical malaria is also observed in the choroid. Current knowledge about occlusion during acute malaria falciparum infection and hypotheses concerning its cause are reviewed in relation to retinal and choroidal pathology.

Adult↗
PubMed1987

[Simultaneous fluo-angioscope. Image superposition for macular photocoagulation].

A new, compact optical instrument developed in clinical work is presented and its optical properties are discussed: it allows simultaneous viewing of a patient's fundus and its fluorescein angiography. Both stereo and mono angiography can be superimposed in the slit lamp in a 1-to-1 juxtaposition of fundus topography and angiogram. In this way very precise transfer of angiographical data is possible. Safety during laser coagulation is increased, and the size of iatrogenic scotomas is thus reduced. The instrument is described, and image superimposition illustrated with clinical examples.

Fluorescein Angiography↗
PubMed1986

[Simultaneous fluo-angioscope: a method for laser treatment close to the macula].

The Simultaneous Fluo-Angioscope is a compact optical device developed in clinical work as ancillary equipment for laser slit lamps. Both binocular and stereoscopic fluorescein angiograms can be directly overlaid onto the patient's fundus in the slit lamp in a 1-to-1 juxtaposition of angiographic data and fundus topography. In this way precise paramacular laser coagulation is achievable with a minimum of scotoma. The overlaying of earlier photos onto the present fundus also makes objective diagnosis of tumors, vessels, and other pathologically significant areas possible.

Fluorescein Angiography↗
PubMed1980

A semi-automated rapid and sensitive microcytotoxicity assay for antibody-mediated cytolysis.

This technique used a Coulter counter to enumerate the target cells remaining after partial lysis with antibody and complement, followed by the destruction of the lysed cells with pronase. Results obtained by this method are compared with those from conventional dye exclusion tests where the final enzymatic step is omitted. Comparisons were made with an anti-Thy-1.2 serum, a monoclonal anti-Thy-1.2 preparation and an anti-H-2k serum. In all cases the semi-automated test gave better results than the dye exclusion test and proved to be highly sensitive and reproducible.

Animals↗
PubMed1980

Investigations on female Onchocerca volvulus for the evaluation of drug trials.

Females of O. volvulus show several typical morphological alterations during their ontogenesis. In order not to attribute such natural findings to the efficacy of drugs in drug trials female worms isolated from untreated patients in Liberia and Togo were examined by light microscopy. Local incrustations could be found regularly on the surface of the female parasite. Different inclusions are described which could often be found. They partially lead to degeneration and calcification. For the evaluation of ovocidal or embryocidal efficacy of drugs the developmental stages of 290 untreated female worms were quantitatively assessed, normal and pathologically altered forms were distinguished. Embryos were obviously not produced continuously but in intervalls of unknown length and frequency. Two third of the females contained embryos and microfilariae, one third showed eggs only or had empty uteri. The number of the developmental stages per female varied considerably. On the average more than 200,000 stages per female were found.

Animals↗
PubMedDate not supplied

Thermal collateral damage in porcine corneas after photoablation with free electron laser.

BACKGROUND: The study describes a quantitative and systematic investigation of the collateral thermal damage during infrared photoablation as a function of wavelength between 2.7 and 6.7 microns. METHODS: Using the tunable Free Electron Laser at Vanderbilt University, Nashville, Tenn, 60 freshly removed porcine cadaver eyes were irradiated at wavelengths between 2.7 and 6.7 microns, at a fluence of 1.3 J/cm2. For wavelengths where no photoablation occurred, fluence was increased to 3.5 J/cm2; pulse length (macropulse) was 4 microseconds, consisting of a train of micropulses (pulse duration 2 ps at a 2.9 GHz repetition rate). The corneal buttons were removed and stained with hematoxylin and eosin (H&E) and analyzed by histologic micrometry. RESULTS: Two thermal damage zones in the remaining tissue were observed: zone 1 showed superficial carbonization and measured between 2 and 4 microns; beyond, the eosinophilic zone 2 measured between 10 and 100 microns. The extent of zone 2 was inversely related to the absorption spectra of the cornea; it was minimal at the 3- and 6-micrometer water absorption bands and maximal at minimal target absorption. CONCLUSION: The results correlated well with a model of the ablation process. The study provides a systematic and predictive element for the determination of collateral thermal adverse effects; it does not yet include pulse length variation as a determining factor.

Animals↗