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Biomedical subjects

J Draeger

Publications and source records attributed to J Draeger.

At least 19 recordsLinked to original sources
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↗
PubMed1992

[Comparative studies of the use of viscoelastic substances in cataract surgery. A randomized study].

In three prospectively randomized groups of patients viscoelastic materials during IOL-implantation have been compared concerning 1. intraocular pressure, 2. endothelial cell count, 3. corneal thickness. Examinations were performed preoperatively, the first, second and fifth postoperative day. There was no statistical difference between hydroxypropylmethylcellulose (2%), hyaluronic acid (1%) and air. Examinations were performed preoperatively the first, the second and the fifth postoperative day. There was no statistically significant difference between all groups of patients, Advantages and disadvantages for routine use of viscoelastic substances are discussed.

Corneal Stroma↗
PubMed1992

[Precision of lenticular thickness in relation to full stroma corneal thickness. Experimental results with the lamellar microkeratome].

In this study 150 pig corneas and 20 human corneas were dissected with an automatic rotating microkeratome for lamellar grafting. The cornea thickness varied between 0.507 mm and 0.829 with an average 0.66 mm. The aim of this investigation was to show the influence of corneal thickness, the chosen diameter and spacing on the precision of cutting lenticles. We did ten series: the pig corneas were dissected at three different intervals of 0.15, 0.25, 0.35 mm and diameters of 9 and 6mm. The human corneas were cut at intervals of 0.4 mm and 0.25 mm and with diameter of 9 and 7 mm. Although the pig corneas were fresh, the intraocular pressure was too low. It was raised with an injection of physiological salt solution to a predefined level. The rotating speed of the trephine blade, the speed of blade advancement and lubrication fluid were kept constant. Ultrasound pachymetry was performed on the center of the corneas before cutting had on the lenticles afterward. We showed that a thick corneal diameter had a negative influence, i.e., the greater the diameter, the lesser the precision; the same was true for the corneal thickness. On the other hand, the intervals had just the opposite effect: the closer they were, the better the correlation. The human eye results were different in quantity but not in tendency, with less striking effects. The average variation for pig corneas was 22% and for human eyes 8%. The best results were received with a large interval, a small diameter, and a normal corneal thickness in human eyes.

Animals↗
PubMed1990

[Morphology of the corneal endothelium following preservation in dextran or chondroitin sulfate containing culture media].

The effects of dextran (group 1) and chondroitin sulfate (group 2) as additives to the culture medium in regenerated donor tissue preservation were investigated. In an experimental study, porcine corneas were incubated for 10 days at 4 degrees C in MEM with 1% chondroitin sulfate or MEM with 6% Dextran (MG 500,000). After a storage period, the corneoscleral disks were incubated in organ culture for 48 h at 32 degrees C, 1,016 cells of group 1 and 777 cells of group 2 were analyzed and the cell area, shape and number of sides were computed. In a control group we digitized 1,023 cells of 20 fresh porcine corneas. The mean area of the cells in group 1 was 345 +/- 212, in group 2 337 +/- 168; in the control group 263 +/- 59 microns2. In the statistical analysis of the data (U test), the preserved tissue had a significantly lower cell count and higher polymorphism than fresh tissue. When group 1 and 2 were compared no significant differences between the preservation media could be found.

Animals↗
PubMed1979

[Special indications for lens implantation (author's transl)].

After hesitation in the indication for the implantation of irisclip-lenses, experience shows that indications which have not yet been planned must be seriously considered: for instance cataract in patients with retinitis pigmentosa. The already highly restricted visual field is not additionally reduced by the wearing of the strong convex glasses. Furthermore the author reports about refinements of the implantation technique.

Adult↗
PubMed1979

[Functional results following implantation of artificial lenses (author's transl)].

Between 1969 and 1979 626 Binkhorst artificial lenses have been implanted, 20 after extracapsular cataract extraction. Functional considerations relating to the indication for implantation are discussed in detail. Visual field and binocular vision in particular are superior in patients with lens implants. In addition, some details are given of surgical methods we have recently adopted.

Adult↗
PubMed1978

[Experiences with the implantation of anterior chamber lenses (author's transl)].

On account of the good results with the new generation of anterior chamber lenses reported by C.D. Binkhorst, the implantation of lenses was begun in 1969 at the Department of Ophthalmology in Bremen and 350 anterior chamber lenses were implanted till 1st Febr. 1977. After the presentation of indications and the operative technique, the problems of postoperative treatment, the results and complications are discussed. According to our experiences up to now, we see in the implantation of iris-supported artificial lenses an enrichment of our surgical possibilities particularly in respect of special functional requirements.

Anterior Chamber↗