Search PubMed⌕ Search

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↗
PubMed1991

[Quantitative determination of corneal sensitivity in idiopathic trigeminal neuralgia and after neurosurgical interventions on the trigeminal nerve].

The purpose of our study was to determine, by use of the electronic Draeger esthesiometer in quantitative, reproductive measurements, the corneal sensitivity in 55 patients with medically treated idiopathic trigeminal neuralgia before and after surgical treatment of the trigeminal nerve and root. 37 patients were included in a prospective study with measurements before and after glycerol rhizotomy, radiofrequency rhizotomy and microvascular decompression (MVD) of the trigeminal root. Moreover, 18 patients were examined retrospectively 7 to 17 years after retrogasserian rhizotomy according to Spiller/Frazier. Corneal sensitivity was determined by the mean value of 3 measurements in each of 5 positions on both eyes. Evaluation of data leads to the following conclusions: In case of neuralgia in the V1 and V2 divisions, corneal sensitivity may decrease without any clinical manifestation. The hypothesis that V2 contributes to corneal innervation got further evidence. Microvascular decompression may lead to a severe decrease of corneal sensitivity. In terms of complications concerning sensory loss of cornea, radiofrequency rhizotomy was the less risky treatment, followed by glycerol rhizotomy, MVD and the retrogasserian rhizotomy according to Spiller/Frazier. Sensitivity affected by prior medical or surgical treatment does not necessarily decrease by further surgical therapy. Postoperatively up to six weeks, corneal sensitivity remained almost the same as shortly after surgical procedure. Keratitis was observed in only one case retrospectively.

Adult↗
PubMed1991

[New osmotic additives to culture media for corneal preservation].

We investigated the effect of hyaluronic acid, molecular weight 250,000 and 500,000 as an osmotic additive to corneal preservation media. Porcine corneal specimens were incubated in organ culture for 8 days, followed by endothelial cell count and ultrasonic pachymetry. The preservation medium MEM-Earle with 2% FCS contained either no additives, 6% dextrane, MW 500,000 2% chondroitin sulfate, 1% hyaluronic acid MW 250,000, or 1% hyaluronic acid, MW 500,000. Whereas corneal thickness was estimated to be about 4 mm in the group without osmotic additives, all other media kept the corneas thin between 700 and 760 microns. The endothelial cell counts after preservation were similar in all groups. As hyaluronic acid is a physiological substance of the eye, it may offer some advantages for corneal perservation.

Animals↗
PubMed1991

[Development of an improved cryopreservation vial for cryopreservation of donor corneas].

To date, corneal cryopreservation has been performed in vials made of glass or plastic, where the cornea is placed in a large volume of culture medium. For improved cell survival, an attempt was made to define freezing curves, which are induced by variations in the temperature in the freezing chamber. Depending on the mass of the specimen to be frozen and on the material conducting the heat, the freezing vials used so far cannot be regarded as optimum. As glass and plastic do not conduct heat very well, we developed a new freezing vial that is especially suitable for corneal cyropreservation. In our experiments, the interaction of the chamber temperature and the temperature near the corneal endothelium were monitored. Additionally, endothelial cell survival was studied by postculturing the tissue and by vital staining. As a result, a cylindrical vial made of aluminum 2-4 mm thick was designed, which enables even heat transfer from the freezing chamber to the cornea. In this vial, the amount of freezing medium could be reduced to 400 microliters, so that the heat from the crystallization process was very low. In a small series the conditions that had been optimal with porcine tissue were tested on ten human donor corneas. The endothelial cell density before (2365 cells/mm2, range 1675-2800) and after cryopreservation (2199 cells/mm2, range 1600-2720) did not differ significantly.

Animals↗
PubMed1991

[Changes in the endothelial cell density after perforating keratoplasty].

We examined 590 endothelial photomicrographs of 327 patients with computerized morphometry; these patients had undergone penetrating keratoplasty in the period from 1981 to 1987. We found a weak negative correlation of r = -0.39 between postoperative endothelial cell density and the postoperative period. The endothelial cell density in the interval 12-24 months postoperatively averaged 1624 cells/mm. This is approximately 380 cells/mm more than described in other studies of that kind. We found significantly higher cell densities for cultured corneas and for corneas of young donors (age up to 39 years) up to 1 year postoperatively. Comparison of the diagnosis groups showed no relevant differences in postoperative cell density.

Cell Count↗
PubMed1991

[Clinical and experimental results with a new fully automatic self-tonometer].

In a clinical study 25 patients being treated at the Department of Ophthalmology in the Hamburg University were instructed in self-tonometry using a new automatic tonometer. In a first sequence, three self-measurements were taken by the patients within 1 min; then a control measurement with a motor-driven hand applanation tonometer (HAT) was taken by a physician. The procedure was repeated 6-10 min afterwards without new local anesthesia. In addition, a dynamometer was applied to 5 healthy eyes in order to test the self-tonometer at higher pressure levels. The correlation of repetitive measurements of the self-tonometer showed good results for the patient measurements (r1 = 0.97, SD1 = 1.66 mmHg, r2 = 0.96, SD2 = 1.47 mmHg) and slightly worse values for the measurements with the dynamometer (r3 = 0.97, SD3 = 2.02 mmHg), probably due to the non-physiological deformation of the eye induced by the dynamometer. To establish accuracy, the results were compared to the HAT. The following results were achieved: (r1 = 0.97, s1 = 1.71 mmHg, r2 = 0.96, s2 = 1.49 mmHg, r3 = 0.97, s3 = 2.69 mmHg). Other studies with the self-tonometer will follow in order to optimize its accuracy and design. Self-tonometry under conditions of microgravity is planned for the 2nd German Spacelab Mission and the Russian Space station MIR. In the future, self-tonometry will play an important part in the management of glaucoma.

Animals↗
PubMed1990

Effects of fibroblast growth factor and chondroitin sulfate on predamaged corneal endothelium. An organ culture study.

Fibroblast growth factor (FGF) and chondroitin sulfate (CDS) were used as supplements in organ culture medium to compare the regeneration ability of corneal endothelium with scattered damages. After 1 week of culturing, cell densities in both FGF-supplemented and FGF + CDS-supplemented groups were not higher than the densities of the control groups. Cells in both groups showed polymorphism. In both CDS-supplemented groups, the corneas were thinner. The cell density in the group supplemented with only CDS was higher than that of the control group, but in the CDS + FGF-supplemented group the cell density was not higher than that of the control and the morphology was even worse. Combining of FGF and CDS in culture medium appeared to be disadvantageous.

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↗