Search PubMed⌕ Search

Biomedical subjects

J Draeger

Publications and source records attributed to J Draeger.

At least 73 records · Page 4Linked to original sources
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

Forces on intraocular lens haptics induced by capsular fibrosis. An experimental study.

Electronic dynamometry measurements, performed upon intraocular lens (IOL) haptics of prototype one-piece three-loop silicone lenses, accurately defined the relationships between elastic force and haptic displacement. Lens implantations in the capsular bag of dogs (loop span equal to capsular bag diameter, loops underformed immediately after the operation) were evaluated macrophotographically 5-8 months postoperatively. The highly constant elastic property of silicon rubber permitted quantitative correlation of subsequent in vivo haptic displacement with the resultant force vectors responsible for tissue contraction. The lens optics were well centered in 17 (85%) and slightly offcenter in 3 (15%) of 20 implanted eyes. Of the 60 supporting loops, 28 could be visualized sufficiently well to permit reliable haptic measurement. Of these 28, 20 (71%) were clearly displaced, ranging from 0.45 mm away from to 1.4 mm towards the lens' optic center. These extremes represented resultant vector forces of 0.20 and 1.23 mN respectively. Quantitative vector analysis permits better understanding of IOL-capsular interactions.

Animals↗
PubMed1990

Measurement of elastic resisting forces of intraocular haptic loops of varying geometrical designs and material composition.

The relationship between experimentally induced intraocular lens (IOL) haptic deformation and resulting elastic haptic counter-resisting forces measured by electronic dynamometry was examined for 34 different IOL haptics of varying material composition and geometrical designs. Poly(methyl methacrylate) (PMMA) and polypropylene loops of similar geometry did not fundamentally differ from one another, although lenses of differing geometry behaved differently. Unlike PMMA and polypropylene loops, soft haptics of poly-HEMA and silicone rubber demonstrated a larger elastic resistance force to the same degree of deformation. This was based upon design characteristics of the lenses and not upon intrinsic properties of the materials, which would have produced the opposite result. By comparative analysis of these dynamometer measurements and considerations of the lens design and elastic properties (including memory) of the component materials, we can calculate the stresses upon the zonular and capsular bag structures during and after IOL implantation.

Biocompatible Materials↗
PubMed1990

[The regression behavior of choroid melanoma following radiotherapy--a new prognostic parameter?].

The present paper reports on follow-up examinations of 246 patients after Ruthenium106 treatment of choroidal melanomas (follow-up time 1.8 to 13 years). In January 1988, 212 patients were alive and free of metastases; 15 had died, 12 of them of melanoma metastases, and 17 could not be followed up. In a retrospective analysis of factors influencing tumor-related mortality, the rate of regression of irradiated tumors was found to be particularly significant. The mean time taken to reduce tumor volume by half was 4.4 months in patients who died of metastases, as against 6.6 months in a matched group of survivors. Using discriminance analysis, the difference was found to be highly significant (P = 0.0058). In the total patient population, a significant correlation was found between pretreatment tumor volume and the probability of metastases (P = 0.058). It may be concluded, though with the qualification that the number of tumor-related deaths was small, that the tumor regression rate is an important factor in the prognosis for patients with Ruthenium-treated malignant choroidal melanomas.

Choroid↗
PubMed1990

[Flexibility of intraocular lens haptics of various geometry and materials].

The relations between the deformation and resulting resilience of lens haptics with various geometries and made of different materials were studied. While there are no fundamental differences between PMMA and PP haptics with identical geometries, the resilience of soft lenses made of poly-HEMA and silicone rubber subjected to the same deformation is significantly higher. On the basis of such measurements it is possible to estimate stress on the capsular bag during and after implantation. In light of recent publications concerning the prevention of secondary cataract, permanent circular tensioning of the lens capsule appears a desirable goal. This requirement is best satisfied with a material with permanently high elasticity, which tensions the equator of the capsular bag over 360 degrees.

Acrylates↗
PubMed1990

[Suitability of different procedures for the sterilization of microsurgical instruments. A review of current and future procedures].

A review of common methods of sterilization is presented. The principles of operation of steam, hot-air, and gas sterilizers, as well as that of a completely new method which uses H2O2 plasma, are described. The suitability of these methods for sterilizing microsurgical instruments was studied. This paper deals in particular with hot-air sterilization, which is preferred because of the low humidity involved. This method was investigated by recording temperature curves during sterilization. Sterilization with hot steam (autoclaving) has been shown to damage instruments by causing corrosion, to which the types of steel used to make these instruments are highly susceptible. A H2O2 plasma sterilization method is described which operates at low temperatures and with very low humidity. Its suitability for microsurgical instruments has been investigated.

Forecasting↗
PubMed1990

[Importance of diagnosis and preoperative care of the conjunctiva].

The conjunctival smear is an important part of preoperative diagnosis. Although the method is very easy there are many possible sources of error. The validity of smear results was studied; the sources of error are discussed in the present paper. The different bacterial flora of the conjunctival sac and the lid margin were investigated. It was shown that eye drop dispensers become contaminated during use. The use of single-dose Ophtiolen has the advantage--in addition to improved hygiene, that no stabilizing agents are used. Preoperative efforts to achieve asepsis have to be continued during the operation. A new adhesive tape specially developed for ophthalmic surgery has been found very effective. This new tape is described.

Anti-Bacterial Agents↗
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↗
PubMed1990

[Perioperative prevention in ophthalmologic microsurgery].

The possible causes of intraocular infections after microsurgical operations on the eye are discussed. Extensive experiments were carried out to investigate infection caused by the patient himself, by the surgeon and by the surgical surroundings. To consider the different aspects involved in "perioperative prophylaxis", we examined the preoperative, intra- and postoperative periods. Conjunctival diagnostics, disinfection of the conjunctival sac, and the operating area were investigated for the preoperative period. Microbiological examinations were carried out to check the possibility of contamination of eye drops, the operating theatre equipment, and of microscopes, etc. The sterilization of microsurgical instruments using different procedures was checked in particular. During the intraoperative period surgical clothing like face masks, gloves and gowns were examined. Sterile sheets for the patient, including an analysis of the respiratory air under the sheet, were monitored. The results are evaluated with respect to their significance for perioperative prophylaxis and the practical consequences for optimal prevention of infection.

Disinfection↗