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J Draeger

Publications and source records attributed to J Draeger.

At least 19 recordsLinked to original sources
PubMed2006

[Clinical evaluation of a new tonometer on the basis of international standard ISO 8612].

BACKGROUND: There is a continuous process of development of new tonometer types following different measurement principles on the tonometer market. A new tonometer working on the dynamic contour measurement principle is currently available for ophthalmologists. This device has special properties, since it determines the intraocular pressure as well as the ocular pulse amplitude. So far, clinical comparison measurements exist between the new tonometer Pascal and the applanation tonometer by Goldmann albeit without any reference to a standard. Besides, these measurements cover only a small pressure range between 7 mmHg and 23 mmHg which is not sufficient for medical diagnosis. PATIENTS AND METHODS: This new tonometer was investigated by clinical comparison measurements according to the currently valid international standard for human eye tonometers (ISO 8612). The tested tonometer determines the intraocular pressure without fluorescein. In an ophthalmogical hospital in Berlin the clinical comparison measurements were carried out by ophthalmologists on 127 patients according to the methods and criteria of the above-mentioned standard. A calibrated AT 870 from the Haag-Streit company served as reference tonometer. RESULTS: The different cornea surface geometries of individual eyes, the variation of tear liquid volume, and also the different elastic properties of the human eye due to a large variation in rigidity led to measurements of intraocular pressure by this tonometer with an excessively high number of outliers p (i) (i = 1, ..., 3) per group (p (1) = 16.28 %, p (2) = 8.85 %, p (3) = 15.69 %, 5.0 % outliers per group only are permitted for the differences method), which do not correspond to the requirements of the international standard for tonometers ISO 8612. This is also shown by application of total method of least squares of regression line (slope a = 0.964, interception b = 2.868 mmHg, standard deviation s (y) = 2.628 mmHg). CONCLUSIONS: The test of conformity of results of clinical comparison measurements to the international standard for tonometers ISO 8612 is the target of this work. The measurement results of the investigated tonometer are analysed and discussed according to this standard. Statements about the medical application of this medical measurement device for ophthalmologists are presented. According to the presented investigations the requirements of this international standard are not fulfilled by the tonometer Pascal.

Equipment Design↗
PubMed2004

[Clinical Testing of New Tonometers on the Basis of the International Standard for Human eye Tonometers ISO 8612].

There is a continuous process of development of new tonometer types following different measurement principles. The impedance measurement method, using the elasticity of the eyeball, allows tonometry even through the eyelid. Two new tonometers based on the impedance principle were investigated by clinical comparison measurements according to the international standard for human eye tonometers ( ISO 8612). The tested tonometers determine the intraocular pressure without topical anaesthesia. The different elastic properties of an individual eyelid and also the different elastic properties of the human eye due to a large variation in rigidity cause serious problems for these measurements. Statistical properties of the two investigated tonometers are presented and discussed. Statements and conclusions about the medical application of these measurement devices for ophthalmologists are made.

Elasticity↗
PubMed2001

[Technical construction, calibration and results with a new intraocular pressure sensor with telemetric transmission].

BACKGROUND: Presently intraocular pressure is measured indirectly by applanation or impression of the cornea. Only isolated values are available with this method. We present a new implantable system for direct and continuos measurement of the intraocular pressure. METHODS: An implantable system consisting of a miniaturized sensor and a telemetric unit was integrated in an intraocular lens. The eye pressure is determined by the sensor, modulated and transduced by the telemetric system. By an extracorporal receiver the signal is demodulated. The electric supply of the intraocular system is achieved by external electromagnetic induction. RESULTS: The telemetric transmission of the intraocular pressure can be achieved with an accuracy of +/- 1 mm Hg and a frequency of registration of 3 values per second. CONCLUSION: Clinical application necessitates further animal trials in vivo.

Calibration↗
PubMed2000

Continuous assessment of intraocular pressure - telematic transmission, even under flight- or space mission conditions.

Fluid shift after entering into microgravity, but also under equivalent flight conditions leads to enormous increase of intraocular pressure. To assess this precisely position - and gravity independent, handsome, automatic tonometers have been developed (German-Spacelab D1-Mission, German-Spacelab D2-Mission, German-Russian-MIR-Mission) telemetric transmission of measuring results of course would find scientific but also functional interest. The same is true for recently designed automatic intraocular pressure sensors, registering intraocular pressure continuously, day and night. Also recently designed new automatic ophthalmodynamometer, allowing directly to assess the intracranial pressure, but also perfusion pressure within the eye also could benefit from a direct telemetric transmission. New technical solutions allowing for the first time even telematic data transmission, are reported.

Humans↗
PubMed2000

[New diagnostic possibilities by a fully automatic applanation tonometer for the ophthalmologist. From the Goldmann principle to automated tonometry].

Applanation tonometry, following Goldmann's hypothesis serves as the gold Standard in tonometry. However, even this approach principle does not always eliminate examiner's error, especially in defining the applanation surface. An automatic surface and force control system is used to increase measurement precision, thus increasing precision and speed of measurement. The instrument, already in use for the patient's self-tonometry, is now also available for the ophthalmologist. An additional coaxial observation system allows precise centering of the applanation surface onto the cornea. This allows new applications of applanation tonometry in daily routine.

Equipment Design↗
PubMed2000

[Revisions in the assessment of fitness for aircraft flying].

So far medical requirements for aviators have been defined by national licensing authorities. For a long while ophthalmological problems, insufficiencies in vision, refraction or color vision, have been responsible for approximately 50% of rejection of applicants for medical reasons. New international regulations proposed as well by ICAO as JAA try to lead to a new balance in these requirements. In general, ophthalmological requirements now allow for lower standards, specifically in refraction, but also in color vision. Also new examination methods are admitted. German and French authorities have announced their opposition being concerned about flight safety for the future.

Aerospace Medicine↗
PubMed2000

Extracellular glutamate and other metabolites in and around RG2 rat glioma: an intracerebral microdialysis study.

The current study determined the extracellular content of glutamate, 10 additional amino acids, lactate, glucose and some antioxidants in a rodent model of malignant glioma, its peritumoral space and the adjacent cortex. RG2 tumors were induced in the right frontal cortex of Fischer-344 rats (n = 10) by a standardized procedure to obtain a maximum sagittal tumor width of 3-4 mm diameter. After confirmation of tumor growth and localization by contrast enhanced MRI three microdialysis probes were implanted simultaneously in the cortex: at the tumor implantation site (tumor), 2 mm caudally, brain around tumor (BAT) and 4 mm caudally (cortex) to the site of implantation. Dialysate concentrations of glutamate were increased 3.9-fold in tumor and 2-fold in BAT compared with cortex. Glycine was elevated 11.4-fold in tumor and 2.6-fold in BAT. Lactate was increased 1.7-fold in tumor, 1.2-fold in BAT. Levels of glucose, ascorbic acid and uric acid were not significantly different in tumor, BAT and cortex. The increased dialysate levels of glutamate and glycine in the peritumoral space may contribute to impaired neuronal function and epileptiform activity associated with this tumor type in humans.

Amino Acids↗
PubMed1999

Differentiation between Spitz nevi and malignant melanomas by interphase fluorescence in situ hybridization.

Spitz nevi are benign melanocytic neoplasias which have distinct pathological features that make the pathological differential diagnosis from malignant melanomas extremely difficult. The Spitz nevi may be misdiagnosed as malignant melanoma and vice versa. Therefore, interphase fluorescence in situ hybridization (I-FISH) was used for a possible discrimination between Spitz nevi and malignant melanomas on the basis of numerical aberrations of the chromosome complement in interphase nuclei of thin sections. Previous studies had shown changes in malignant melanomas which were not found at the same level in normal tissue or benign tumors. Thin sections of archival paraffin material from 42 Spitz nevi with different histological type and grade of anomaly were subjected to FISH-analyses using commercially available biotinylated and/or digoxigenated alphoid DNA probes of chromosomes 1, 6, 7, 9, 17 and 18, which were applied in combinations in a two- or three-color-FISH. Unaffected epithelial areas from the same sections served as. The obtained data were compared with those collected previously from thin sections of malignant melanomas prepared in the same way. Due to the sometimes limited nevus area investigated, the number of evaluable nuclei was lower than expected from previous experiences with malignant melanomas. Therefore, only 20 nevi could be reliably evaluated. The comparison of the group of Spitz nevi with the group of controls did not show any significant difference regarding chromosomes 1, 6, 7, 9 and 17 (Wilcoxon test). The method used to detect chromosomal loss or gain in the individual Spitz nevi demonstrated only two nevi (one of the spindle cell type with a low to middle grade of anomaly, the other of the epitheloid cell type with a middle grade of anomaly) with a gain of chromosome 7 and chromosome 17, respectively. So, with respect to the histological type and grade of anomaly, no numerical aberrations could be detected in Spitz nevi. The comparison of the group of Spitz nevi with subgroups of malignant melanomas (metastatic, non-metastatic, melanomas with a thickness <1.5 mm and melanomas with a thickness >2. 0 mm) and with the whole group of malignant melanomas showed significant differences concerning chromosome 9 (Mann-Whitney U test), signal indices, which were higher in the melanomas than in the Spitz nevi. Regarding chromosomes 6, 7 and 17 no significant differences could be shown, although a trend of gain in melanomas and of loss in Spitz nevi was observed of these chromosomes.

Adolescent↗
PubMed1999

Intracranial pressure in microgravity conditions: non-invasive assessment by ophthalmodynamometry.

BACKGROUND: As well known from former manned spaceflight experiments (German D2-Mission/German D1-Mission 1985/German-Russian MIR-Mission 1 992/German-D2-Mission 1993), fluid shift after entry into microgravity leads to a rapid increase in pressure and volume within the upper compartments of the human body. This has been proven by precise measurements with automatic selftonometers for intraocular pressure. HYPOTHESIS: There is little doubt, that a very similar--even more, marked--increase of intracranial pressure happens soon after entry into microgravity. This may be the cause for some of the reported hormonal and even neurological changes in metabolism. There is no non-invasive method to assess these important increases in pressure. METHODS: Ophthalmodynamometry in general allows for rather precise estimation of intracranial BP, but so far the method was too complicated for routine application, specifically in spaceflight conditions. Therefore, using the microprocessor controlled technology of our automatic selftonometer we have designed a very precise automatic instrument which can be applied by the astronaut/kosmonaut. The measurement takes only a few seconds. CONCLUSIONS: This easily applied, non-invasive method would allow for completely new insights into these important changes and explain some of the clinical consequences noted so far.

Astronauts↗
PubMed1998

[Refractive surgery and flight safety].

For both VFR and as IFR flight, visual assessment is the major source of information for the pilot. The new possibilities for change of refraction by means of corneal refractive surgery have led to an increasing demand from pilots for these new methods. Can these methods successfully be applied for aviation purposes? The valid regulations for medical standards of pilots, as well as the future international regulations such as JAR and ICAO, are explained in this respect. A report is given on the work of the Advisory Board of the German Federal Government Air Traffic Authority and on the cases treated so far and their outcome, and recommendations are expressed. Concerning the legal situation and clinical experience, advice for pilots, aviation medical examiners and ophthalmologists is given.

Accidents, Aviation↗
PubMed1998

[Development of perimetry since antiquity].

Even in greeque medicine the visual field has been described and recognized. Besides the visual acuity, references are given on early observations of the visual field and its defects. Ptolemaeus (87-165 n. Chr.) first mentioned a method to test the visual field and also gave some physical definitions. Further developments are described in detail. From this oldest method it was a long way to develop techniques for measurement and quantification which could be used in clinical practice. There was an amazing high number of different inventions and parallel developments of methods testing the visual field in the last century.

History, 15th Century↗
PubMed1997

[Biomechanical study of corneal stability after photorefractive keratectomy].

BACKGROUND: Photorefraktive keratectomy (PRK) is the most frequent refractive surgical procedure worldwide. The central corneal thickness is reduced due to removal of the anterior stroma, including Bowman's layer, with a laser beam. This procedure results in considerable alterations of the corneal structure. What does this mean for the mechanical properties of the cornea? METHODS: Intraocular pressure was increased via a 180 degrees tilt. Before and during this procedure, corneal topography was measured by photokeratoscopy. We examined 26 patients after PRK and 25 controls who had not undergone any surgical procedure. RESULTS: The corneal center flattened by 0.038 +/- 0.05 dpt (P > 0.05) in the PRK patients and by 0.187 +/- 0.045 dpt (P < 0.05) in the control group. PRK patients within 1 year after operation showed a minimal central corneal steepening, whereas PRK patients after more than 1 year showed a reaction similar to that in normal corneas (P < 0.05). CONCLUSION: Corneal stability is altered after PRK. After 1 year corneal stability seems to normalize due to stromal remodelling.

Adult↗