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Biomedical subjects

B Jean

Publications and source records attributed to B Jean.

16 recordsLinked to original sources
PubMed1992

Selective laser-induced inactivation of proteins (SLIP) by labelling with chromophores.

Coupling a fluorochrome (e.g. fluorescein-isothiocyanate, FITC) to a molecule can enhance specific laser light absorption, thus leading to alteration or even destruction of the molecule itself. Therefore antibodies were labelled with FITC (absorption maximum 480 nm) and irradiated with laser light (488 nm) under various conditions. Inactivation of antibodies could only be achieved at the absorption maximum of FITC (as measured by direct and indirect immunofluorescence). Positive linear correlation exists between the amount of destruction and both exposure time and energy. Similar destructive effects were obtained when FITC-labelled peroxidase was irradiated. In these cases, enzyme activities measured by absorption photometry also showed a positive correlation to the total amount of energy transferred. Non-labelled proteins were not affected by irradiation. So we conclude that labelling of proteins with fluorochromes provides a highly specific means of selection of target molecules to be destroyed or inactivated. The method is based upon the laws of linear optics and is different from photodynamic or photochemical actions. The destructions observed are most likely caused by thermally induced changes of the molecules' tertiary structure.

Antibodies↗
PubMed1991

[Real time eye tracking--principles and quantification].

Tracking and quantification of eye movements in real time is a prerequisite for future computer assisted laser positioning for diagnostic or therapeutic purposes. Principles of TV-image processing are described: tracking of contrasts and pattern recognition tracking by object correlation; their relevance for tracking retinal targets is illustrated using authentic video material. For practical use, the pattern recognition technique qualifies better. The influence of the systems variable parameters on retinal target pursuence is described. Automatic target pursuence of authentic eye movements reached tracking success rates well above 90% thus outperforming manual tracking by one order of magnitude.

Computer Graphics↗
PubMed1991

[Validity and reproducibility of confocal corneal measurements].

In order to verify reproducibility and validity of confocal measurements of the cornea we examined a well known biological model: Increasing corneal thickness under hypoxic conditions during contact lens wear. The method verified increasing thickness with high significance. In addition, reproducibility was determined within a range of 5 mu. As a result, confocal measurements proof to be a powerful tool for topographical reconstruction of corneal shape.

Algorithms↗
PubMed1991

[Image of the cornea with the scanning laser ophthalmoscope].

With a scanning laser ophthalmoscope (SLO), a hexagonal reflex phenomenon can be observed, which originates from the tear film and corneal tissue layers. Time motion analysis verifies that it is possible to discriminate between the cornea and tear film.

Cornea↗
PubMed1990

[The simultaneous video fluoangioscope].

The present paper describes the video simultaneous fluoangioscope. It is based on the Rodenstock simultaneous fluoangioscope, an accessory for use with the laser slit-lamp. It has been proving its clinical usefulness since 1984. Hitherto, its optical superimposition of the corresponding fluorescein angiograph onto the actual fundus view was based on angiographic film as an information carrier. Digital fluorescein angiography (videoangiography) has meanwhile made film superfluous while at the same time opening up new possibilities. The video simultaneous angioscope superimposes a selected video half-frame onto the fundus, thus transferring angiographic data and facilitating safe and easy coagulation. The advantages and new possibilities arising from them are discussed and the system peripherals are described. An illustration shows the superimposition of the images when looking through the slit-lamp.

Equipment Design↗
PubMed1990

[Examinations of the cornea and anterior chamber angle region with a laser tomographic scanner (LTS)].

The Laser Tomographic Scanner LTS based on laser scanning and confocal detection is a system to generate and measure optical section images. The periphery of the cornea and the anterior chamber angle region is shown in the horizontal section image with high image quality and high signal-to-noise ratio. 130 patients and 163 eyes were examined in this way. First experience shows possible applications for special clinical situations. Using horizontal optical section images, a procedure is generated to measure the anterior chamber angle without contact or local anesthesia with a reproducibility of 2 degrees. Horizontal section images clearly demonstrate changes of anterior chamber angle depth following e.c. cataract extraction and implantation of posterior chamber IOLs. Using the generated measurement procedure, these changes could be quantified.

Adult↗
PubMed1990

[Laser-induced occlusion of corneal blood vessels with variable emission and absorption].

Laser light has repeatedly been proposed for the occlusion of corneal neovascularizations. Priority has to be given to minimize laser energy in order to limit side effects such as corneal burns. We investigate the influence of variable emission wavelength using a dye laser or dye-enhanced absorption with intravenous sodium fluorescein. Laser energy can be reduced using intravenous dyes at vessel diameters less than 50 microns. Permanent occlusion is achieved in 43% instead of 28% without dye-enhanced absorption. Vessels measuring greater than 50 microns in diameter can be occluded best at lowest laser energy levels when 575 nm laser light is used, which approximates the absorption maximum of hemoglobin.

Absorption↗
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↗
PubMedDate not supplied

Silicon cast method for quantification of photoablation.

BACKGROUND: Topometry and measurement of photoablation patterns are key questions for keratorefractive photoablation. Ablation rates have been determined previously by either tissue perforation or by micrometry performed on histologic sections. METHODS: A three-dimensional cast of cornea after irradiation was made by using a two-component silicon gel that polymerizes within minutes, thus preserving the corneal topography immediately after photoablation. Polymerization is athermal and nontoxic. The resulting silicon blocks were cut perpendicularly to the anterior surface and measured by calibrated light microscopy. RESULTS: The silicon surface is extremely smooth and the accuracy of the cast is better than 0.25 micron. Reproducibility and long-term stability were demonstrated for casts of photoablated polymethylmethacrylate. Thus, ablation rates and profile, volumetry, and topometry can be determined following laser ablation. The method has been applied for 193-nanometer excimer laser in vitro irradiation of the human cornea. Ablation rates in Bowman's layer and stroma for various radiant energies and distinct pulse numbers were found to be in agreement with published data, and an incubation effect for the first laser pulses could be demonstrated. CONCLUSIONS: The method is nondestructive, accurate, inexpensive, practical, and reduces requirements for laboratory animals.

Animals↗
PubMedDate not supplied

Photorefractive keratectomy as a second attempt to correct myopia after radial keratotomy.

BACKGROUND: Undercorrection after radial keratotomy is not uncommon. To correct the residual refractive error, several techniques are available including photorefractive keratectomy. METHODS: We report five eyes of four patients, which remained undercorrected following radial keratotomy and underwent photorefractive keratectomy with an excimer laser (193 nm) to correct the residual myopia, with a follow up of 6 months to 1 year. RESULTS: The corneal-healing response was similar to that of corneas treated by photorefractive keratectomy alone. No permanent corneal scarring occurred. The average preoperative refraction before photorefractive keratectomy was -2.25 +/- 0.55 diopters; it was close to plano (+0.12 +/- 0.26 D) after 6 months. One eye regressed 0.50 D between 6 months and 1 year. Best-spectacle corrected visual acuity did not change. CONCLUSIONS: Excimer laser photorefractive keratectomy seems to be effective as a second procedure in eyes undercorrected following radial keratotomy.

Adult↗