Biomedical subjects

J Draeger

Publications and source records attributed to J Draeger.

At least 55 records · Page 3Linked to original sources

PubMed1993

Self-tonometry under microgravity conditions.

During a space mission flown in microgravity early changes in intraocular pressure due to the fluid shift effect in microgravity were analyzed with an automatic self-tonometer. In total, 13 pressure readings per eye were obtained during the mission. The first pressure readings 16 min after reaching microgravity revealed a 92% rise in intraocular pressure compared to the daytime-correlated baseline data on earth followed by an adaptation phase lasting for several hours. Diurnal pressure profiles during the mission showed no relevant difference in altitude and amplitude.

Humans↗

PubMed1993

[Principles of measurements in tonometry at the time of Albrecht von Graefes to D2 mission and self-tonometry].

There is no doubt that an elevation of intraocular pressure (IOP) precedes any morphological or functional glaucomatous damage for years, if not decades. Surprisingly, in the present glaucoma literature methods for a quantification of such a damage are prevailing. There might be two reasons for this: The question of tonometry is supposed to be perfectly and definitely solved or tonometry as the most significant diagnostic tool for an early diagnosis of glaucoma has been lost out of sight. Two aspects shall be discussed in the following: Firstly, we want to deal with an improved glaucoma management especially in the early phase of the disease. The question is when and how often should tonometry be performed to detect the typically greater diurnal fluctuations of IOP in glaucoma. This has already been pointed out in particular by Sampaolesi and Hager. Secondly, the technique of the most appropriate tonometer for this purpose is outlined. Important aspects are the accuracy of the instrument according to the standard set by the Goldmann applanatation tonometer as well as safety and easy handling. Like in other branches of medicine where the patient is more and more involved in his own disease control (eg self-measurement of blood pressure in patients with arterial hypertension), self-tonometry is likely to become a revolutionary step towards an improved management and follow-up of glaucoma. These are the objectives we should concentrate on. Technical solutions, clinical applications and experiences are demonstrated.

Circadian Rhythm↗

PubMed1993

[Surgical measures in congenital glaucoma].

An overview about the classification, diagnostic and therapy of congenital glaucomas is given. Tonometry, gonioscopy, corneal diameter measurements, oculometry and the evaluation of the optic disc are the main diagnostic criteria. Goniotomy is the operation of choice. The technique of goniotomy and their modifications leading to cyclodialysis ab interno are described. Own long-term results of goniotomy are finally demonstrated.

Child↗

PubMed1993

[Results of self-tonometry during the 1st German-Russian MIR mission 1992].

The 1st German-Russian MIR mission 1992 is one result of the agreement about technical and scientific cooperation between Germany and the former Soviet Union. Fourteen experiments have been performed during the 8-day manned space mission, one of which was called "TON": self-tonometry in mu-gravity. A total of 70 measurements of intraocular pressure (IOP) was performed in the SOJUS TM capsule as well as in the MIR space station with the automatic self-tonometer. The first pressure readings 16 min after reaching mu-gravity revealed a 92% rise in the IOP compared to the baseline data on earth followed by an adaptation phase lasting several hours. Important information about the handling of the self-tonometer in mu-gravity was obtained. Its use is also planned for the 2nd German D-2 Spacelab-Mission in March 1993.

Adult↗

PubMed1993

[Pressure-induced change in corneal curvature in patients with refractive surgery and unoperated probands].

Helmholtz suspected there was a connection between intraocuclar pressure and lateration of corneal curvature. With a view to potential changes in corneal stability following different refractive procedures, we tried to demonstrate these side effects by increasing the intraocular pressure. A tilting-table was used to induce a rapid pressure increase via the fluid shift. Corneal curvature was measured by photokeratoscopy before and after pressure changes. The results were different in corneas subjected to radial and photorefractive keratotomy than in intact corneas. We suggest a physical model that might provide an explanation.

Adolescent↗

PubMed1993

[H2O2 low temperature plasma sterilization. New possibilities for use with eye surgery instruments].

The H2O2-low-temperature-plasma-sterilization (STERRAD 100) works with a temperature below 50 degrees C (140 degrees F). This system is appliable for thermostabile materials as well as for thermolabile materials. The efficancy of this new system is shown by a biological test with Bacillus pumilus spores. 5 typical ophthalmic surgical instruments were contaminated. After sterilization the numerical reduction of the microorganisms had to be at least 6 log levels. Corrosion caused by hydrogene peroxide was excluded after exposing steal with a high quantity of this substrate. Electromicroscopy analysations of the surfaces of stainless steal after LTP, steam sterilization and hot-air sterilization are compared. Options and limitations of this new sterilization technique are discussed. A newly developed operating system with a complete instrumental box (OP-Set) will be introduced.

Bacillus↗

PubMed1993

[Aviation and space flight ophthalmology].

So far it has not been possible to adapt man genetically to the specific environmental conditions of flying. A variety of disturbing factors act on the human body and affect its vital as well as sensory functions, vision being considered the most important sense for providing information. The effects of oxygen deficiency caused by increasing altitude, acceleration and centrifugal force affecting visual function, ocular motility, and pupillary reactions are well known. Like visual illusions, vibrations, high accelerative forces, high illuminance and glare at high altitudes impair the visual perception of the environment. In space flight further problems ensue from weightlessness and short-wave radiation. The high medical standards that must be met by the eyes of flying personnel, as will as for air-traffic controllers, result in the enhancement of flight safety. After operations on the cornea or retina or cataract operations in pilote, the retinal findings and DOP must be monitored closely. Special attention must be paid to means of visual aids, corrective lenses, contact lenses, and intraocular lenses. Ophthalmology is a very important element of aviation and aerospace medicine.

Eye Diseases↗

PubMed1993

[Physical technical calibration of a new self-tonometer].

The microprocessor-controlled applanation tonometer was calibrated in force measurement and area detection by using weights and silicon calibration pistons. This makes it possible to compare the technical precision of the instrument under standardized conditions and the results of previous clinical examinations. With the instrument in a vertical position, the force measurements meets the official calibration requirement. Force measurements in a horizontal position will follow in order to demonstrate that exact measurements can be taken with the instrument irrespective of position. A suitable method for calibrating the optical sensor by using the silicone pistons for area detection is shown. This method is to be extended by using calibration pistons of different diameters, which are within the permitted calibration tolerances.

Calibration↗

PubMed1993

[Optimizing the automatic self-tonometer by an acoustic control signal and changed fixation optics].

An automatic self-tonometer must fulfill special requirements from the point of view of precision as well as user-friendliness. The sensor that applanates the cornea must be perfectly centered on the vertex in order to measure the intraocular pressure correctly. The modified version of the self-tonometer has been equipped with an acoustic control signal and a modified fixation lamp that facilitate its use. In order to analyze the effectiveness of these hardware changes, we compared the modified tonometer to the existing self-tonometer in a randomized study with 30 patients. Reference was the Draeger hand-held applanation tonometer. The results show comparable precision; however, the percentage of error measurements in the modified tonometer was considerably lower. This is a definite improvement in the development of the self-tonometer.

Adolescent↗

PubMed1993

[Endothelial cell transplantation in a model].

Human donor corneas that were unsuitable for transplantation were denuded of their endothelium and then used as substrates for seeding in vitro cultured human or porcine corneal endothelial cells. Only cells that expressed an endothelial-like morphology in vitro formed a monolayer on the denuded matrix whereas fibroblast-like cells showed no redifferentiation. The maximal achieved cell density was 3,500 cells/mm2 if porcine cells were used and 1,800 cells/mm2 for human cells. Adhesion of the cells was best if the subendothelial matrix was carefully prepared mechanically. Moreover, cell seeding was improved by slight centrifugation. Fibroblast growth factor (FGF), which enhanced endothelial cell proliferation in vitro, did not influence proliferation after cell transplantation, but seemed to allow better regeneration of the newly formed monolayer on the corneas.

Animals↗

PubMed1992

Self-tonometry: technical aspects of calibration and clinical application.

Self-tonometry could be established as an important diagnostic tool in the early diagnosis and follow-up of glaucoma provided that a self-tonometer is precise, safe and easy to use. Furthermore, it has to comply with the legal standards for tonometer calibration. A new software-controlled detection system for the self-tonometer permits the evaluation of external factors during the measurement which influence the precision of the tonometric readings. The updated version of the self-tonometer (ST) was compared to the Draeger hand-held applanation tonometer (HAT) in a clinical study with 82 patients (151 eyes). The results show a regression line characterized by a slope of 0.99, an y interception of 1.41, a correlation coefficient of 0.96 and a standard deviation for the ST readings of +/- 1.78 mmHg. Self-tonometry improves the IOP monitoring as well as patient compliance and therefore is a potential diagnostic tool in the management of glaucoma.

Calibration↗

PubMed1992

[Technical problems in microsurgical processing of preserved donor tissue].

The microsurgical processing of longterm preserved tissue is still a problem for lamellar and perforating keratoplasties. Advantages of donor tissue cut with rotortrephines versus manual trephines are presented. Optimal possibilities of examination and storage of donor tissue are explained. A lamellar microkeratome, an artificial anterior chamber for corneoscleral discs and a refractive workbench for non-freeze modification are shown.

Corneal Transplantation↗

PubMed1992

[Prerequisites for the use of preserved donor tissue in perforating and lamellar keratoplasty].

The longterm tissue culture is performed at the University Eye-Hospital of Hamburg since 1985 with a standardized procedure. The number of donor material and operations in the first 7 months of 1991 are reported. Preparation, storing and HLA-typing of the tissue are considered. The technical working up of the stored tissue for penetrating and lamellar keratoplasties will be explained.

Corneal Transplantation↗

PubMed1992

[Aesthesiometry of the cornea after refractive corneal surgery].

The corneal sensibility was examined with the aesthesiometer of Draeger in 41 patients after refractive corneal surgery, 31 patients after radial keratotomy, 5 after epikeratophakia, 5 after excimer laser ablation. It could be shown that after radial corneal incisions the sensibility remains normal. After epikeratophakia the corneal sensibility is asensible even 3 years after operation. The lenticle periphery shows an increase of sensibility after 6 months. Excimer patients with "haze" showed a significant hyposensibility in the centre. The central sensibility showed normal values after a normal corneal wound healing.

Adult↗

PubMed1992

Effect of dextran on predamaged corneal endothelium: an organ culture study.

Dextran T500 was used as a supplement in organ culture medium to evaluate its effect on corneal endothelium with disseminated damage. After 1 week of culturing, the control group showed an intact endothelium throughout the entire cornea. However, in the dextran-supplemented group, multiple endothelial necroses were observed in 5 of 10 corneas. Besides, intracytoplasmic vacuoles and granules, deposits on the endothelial surface and widened intercellular spaces were quite numerous. The potential toxicity of dextran to degenerated corneal endothelial cells may be responsible for these findings.

Animals↗

PubMed1992

[New aspects of surgical treatment of glaucoma. Comparison of viscoelastic substances in chamber angle surgery].

The development of new viscoelastic substances opens up new perspectives for chamber angle surgery under direct view. The success of "Cyclodialysis ab interno" treating children with glaucoma is often reduced by scar formation of the cleft. Therefore four different viscoelastic substances were instilled during an animal experimental study into the cleft and compared in their effect. We used hyaluronic acid with different molecular weight (Healon and Healon GV) and cross-linked forms of hyaluronan as a fluid and a gel (Hylan fluid and Hylan gel). A cyclodialysis ab interno was performed on 14 eyes of cynomolgus monkeys. The functional results (tonometry, outflow facility, autoradiography) and the morphological findings will be presented and their consequences for an extended indication of the cyclodialysis ab interno will be discussed.

Animals↗

PubMed1992

[2 years self-tonometry. Acceptance and results].

For more than 2 years we have been trying out a microprocessor-controlled self-tonometer to determine its clinical usefulness. Most of the measurements were taken with two instruments (A and B). In vitro calibration series on human donor corneas gave good results over the whole pressure range. In a patient series both instruments were compared with the established hand-held applanation tonometer put out by Draeger (HAT). Each self-tonometer was applied three times, followed by a controlling measurement with the HAT. The correlation coefficient between instrument A and HAT was 0.85 with a standard deviation of +/- 1.9126 mmHg. Instrument B showed a better correlation (r = 0.904), the standard deviation was similar to tonometer A (SD = +/- 1.8598 mmHg). Most of the values obtained by the self-tonometers-about 50%-deviated from the corresponding HAT values by +/- 1 mmHg. The new measurement principle was accepted by 75% of all patients. Improvements in the details are planned in order to simplify tonometer handling and increase the accuracy and precision of the measurements.

Adolescent↗

PubMed1992

[Effect of postmortem duration on endothelial cell density in short-term culture with McCarey-Kaufman medium. An experimental study with Swine corneas].

It is recommended by the Eye Bank Association of American that the post-mortem time of donor tissue stored in intermediate storage should not exceed 6 h. In an experimental study we investigated the impact of post-mortem time on the storage of corneas kept in McCarey-Kaufman medium. Eyeballs of freshly slaughtered pigs were kept in moist chamber storage at 4 degrees C for 0, 6, 12, 24, and 48 h. Subsequently, corneal-scleral rims were dissected and stored in MK-Medium for 2 days at 4 degrees C. The corneas were stored in organ culture for another 2 days at 31 degrees C in MEM medium containing 10% fetal calf serum. A control group consisted of corneas that had been stored in organ culture for 2 days. Morphometric analysis revealed no significant changes in endothelial cell density compared to control corneas after up to 24 h of moist chamber storage prior to storage in MK medium. A significant decrease in endothelial cell density could only be detected in corneas that had been kept in moist chamber storage for 48 h before MK medium storage. We conclude that the recommendation that only donor corneas with short post-mortem times be used may exclude large amounts of potentially feasible tissue for penetrating keratoplasty.

Animals↗