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Biomedical subjects

J Draeger

Publications and source records attributed to J Draeger.

At least 91 records · Page 5Linked to original sources
PubMed1990

[Precision of lamellar refractive corneal lenticules].

We studied the changes in central lenticular thickness in 40 porcine corneal specimens subjected to refractive modification on the "Hamburg Refractive Bench." The changes in thickness attempted were +0.1 mm (group 1), +0.2 mm (group 2), -0.15 mm (group 3), and -0.25 mm (group 4). The lenticular thickness was determined by ultrasound in nine positions. When the intended changes in central corneal thickness were compared with the actual changes, the findings were +0.1047 in group 1, +0.169 in group 2, -0.1047 in group 3, and -0.2185 in group 4. We conclude that minor modifications in lenticular thickness can be achieved with high precision, but for large corrections in the hyperopic direction, only 85% of the desired changes can be accomplished.

Animals↗
PubMed1990

[Self-tonometry--technical possibilities and clinical significance].

Since 1975, four selected glaucoma patients and their relatives have attended the Department of Ophthalmology at Hamburg University, for instruction in home tonometry using the Draeger motor-driven hand applanation tonometer. Two glaucoma patients whose intraocular pressure (IOP) was measured by their physicians were also included, in order to analyse long-term monitoring of the IOP by medical staff. Home tonometry has been performed over several years and has proved to be a reliable and precise diagnostic tool allowing valuable treatment and close follow-up of glaucoma, especially in severe forms of glaucoma. The benefits of patient's participation in their own disease monitoring, e.g., self-measurement of blood pressure in patients with arterial hypertension, show that such involvement can lead to more diagnostic security and better compliance. On the basis of applanation tonometry calibrated by Goldmann, new concepts of microprocessor-controlled assessment of the applanation area are outlined. These sensor tonometers will allow automatic, precise and fast self-measurement of the intraocular pressure, opening up new perspectives in the management of glaucoma.

Adult↗
PubMed1990

The role of serum-supplements in organ culture for pre-damaged corneal endothelium.

Thirty-six pig corneas were shaken in 0.18% NaCl to induce disseminated corneal endothelial damage. After treatment, the corneas were divided and cultured in 3 different combinations of media to study the effects of serum-supplements in corneal endothelial regeneration. There were MEM+10% FCS (FCS-group; n = 10); MEM+10% Nu-Serum (Nu-group; n = 10) and MEM only (control group; n = 16). After one week of culturing, most of the corneas in all 3 groups, despite the pre-damage, kept intact endothelia. This means that the endothelia were repaired whether the sera were supplemented or not. The cell densities of each were 2,454 +/- 450 cells/mm2, 2,776 +/- 476 cells/mm2 and 2,627 +/- 558 cells/mm2 respectively. The differences between each group were statistically insignificant. The morphological findings were also without much difference. When considering the risk of serum induced hypersensitivity, FCS can be replaced by Nu-Serum in the organ culture medium for corneal preservation. Since the advantage of serum-supplements in medium-term organ cultures seems limited, the necessity of serum supplements should be further reevaluated.

Animals↗
PubMed1990

[Endothelium protective effect of the high viscosity substances hyaluronic acid and methylcellulose in mechanical damage].

We investigated the protective effect of the high-viscosity substances sodium hyaluronate (1%) and methylcellulose (2%) on corneal endothelium in the face of severe mechanical insult. An intraocular lens was drawn across the endothelium of porcine corneas with standardized conditions. We used different compression forces. Methylcellulose and sodium hyaluronate were used as lubricating substances in the experimental groups, while balanced salt solution (BSS PLUS) was used in the control group. In this study no significant protective effect of high-viscosity substances against strong direct mechanical damage was generally demonstrable. Only one group in which a moderately strong compression force was applied showed significantly less smaller endothelial cell loss when methylcellulose was used. The most important function of viscous substances is therefore to prevent a collapse of the anterior chamber and to prevent any contact of the intraocular lens or of instruments with the endothelium. Any mechanical contact with the endothelium means an irreversible endothelial cell loss.

Animals↗
PubMed1990

[Clinical value of new tonometers].

In a clinical study four different tonometers [a hand-held applanation tonometer (HAT), a tonometer that works according to the principle of Mackay-Marg and two noncontact tonometers (NCT A und NCT B)] were compared with respect to accuracy and precision. In a randomized sequence, two physicians took six measurements of both eyes of 99 patients using the four different instruments. The interval between the two measurements in one eye was 3 min. The correlations of repetitive measurements for one tonometer in one eye showed good results for HAT (r = 0.985, SD = 1.66 mmHg), but significantly worse values for the other three tonometers (Mackay-Marg type: r = 0.85, SD = 3.5 mmHg; NCT A and NCT B: r = 0.91, SD = 2.93 mmHg). To establish the accuracy, the pressure values of the Mackay-Marg type and NCT A and NCT B were compared with those of the well-established HAT. The results were as follows: Mackay-Marg type: r = 0.84, SD = 3.78 mmHg; NCT A: r = 0.86, SD = 4.55 mmHg; NCT B: r = 0.89, SD = 3.26 mmHg). We conclude that the three tonometers tested (one based on the Mackay-Marg principle and the other two on the non-contact principle) are not suitable for clinical and scientific use.

Adolescent↗
PubMed1990

[Application of experimental findings of cryopreservation of animal tissue to results of cryopreservation of human tissue].

In order to compare the results after experimental corneal cryopreservation of porcine corneas to human tissue we cryopreserved several human corneas that were not suitable for transplantation. The corneas were frozen in a medium containing 2% chondroitin sulfate, 15% DMSO, and 20% fetal calf serum in MEM-medium to -196 degrees C and thawed at 37 degrees C in a waterbath. Subsequently they were kept in organ culture for 24 h. After vital staining with trypan blue and alizarin red S they were evaluated morphometrically. Endothelial cell densities after the experiment ranged between 47% and 64% of the endothelial cell counts revealed before cryopreservation. Human corneal endothelium showed enlargement of single nucleated cells, and large numbers of giant cells with one or two nuclei but only few multinucleated giant cells and only few necrotic spots compared to porcine tissue in which multinucleated giant cells and large necrotic areas were a frequent finding. We conclude that human corneal endothelium is less sensitive to the freeze-thaw trauma than porcine tissue. Porcine tissue can be used as a susceptible model for the development of new methods of corneal cryopreservation.

Adult↗
PubMed1989

Microprocessor controlled tonometry.

Microprocessors have enabled new techniques to be applied to the design of tonometers. Three new microprocessor controlled tonometers, one operating to the principle of Mackay-Marg (Tono-Pen) and two non-contact airstream tonometers (Pulsair and CT-10) have been examined using as a reference Goldmann and the Hand Held Applanation Tonometers (Draeger-HAT) which used the Goldmann applanation principle. The non-contact tonometers produce a conically formed airstream with top speeds of 90 m/s (CT-10) and 70 m/s (Pulsair) which at the moment of pressure measurement applanates the cornea exactly with a diameter of 4 mm. The readings of the microprocessor controlled tonometers correlate well with the readings of HAT (Tono-Pen r = 0.8414 and s = 3.783, CT-10 r = 0.8606 and s = 4.5477, Pulsair r = 0.8968 and s = 3.2641, where r is the correlation coefficient and s is the standard deviation in mmHg). Repeated measurements with one tonometer give the following standard deviations (HAT 1.6617, Tono-Pen 3.4969, CT-10 2.9179, Pulsair 2.9434). Although the three new instruments are able to measure the intraocular pressure in a wide range they do not work with the same precision as the classical applanation tonometer.

Evaluation Studies as Topic↗
PubMed1989

[Clinical and experimental evaluation of the so-called Tono-Pen tonometer].

The measuring accuracy and reliability of the new Tono-Pen tonometer, which works on the Mackay-Marg principle, were tested on isolated human and pigs' bulbi and on 24 patients. On isolated pigs' bulbi the Tono-Pen indicated the true pressure, whereas the pressures measured on isolated human bulbi were too high and the range of scatter was wider. On patients' eyes the values obtained with the Tono-Pen correlated well with those measured with the hand applanation tonometer (r = 0.92), although the values measured with the Tono-Pen again higher (mean 4.5 mm Hg). As indicated by autocorrelation of repeated measurements, the Tono-Pen appears to be mainly responsible for the difference between the two instruments. The standard deviation of the autocorrelation of the Tono-Pen values was 4.5 mm Hg, that of the hand applanation tonometer only 1.2 mm Hg. The considerable standard deviation of the Tono-Pen measurements may be due to the structure of the human cornea, and in particular Bowman's membrane. The reproducibility of Tono-Pen measurements is too low for it to be recommended for ophthalmological diagnosis.

Animals↗
PubMed1989

[Progress in early detection and follow up of glaucoma].

The importance of Hans Goldmann's contributions to clinical tonometry is discussed in detail. One example is the principle of an applanation diameter of 3.06 mm, which was established by him and is still the basis for the various methods of clinical tonometry today. Therefore, further advances in this field can only be concerned with facilitating the application of this principle. An instrument which can be used by both physician and patient is described. By facilitating more frequent tonometric examinations it would ensure much better glaucoma control than is at present possible. A further application of a self-test tonometer of this kind, which is not affected by gravity, is space medicine. It is planned to use the instrument in the German Spacelab D2 mission in 1991.

Follow-Up Studies↗
PubMed1989

A model to induce scattered cell damage in the corneal endothelium.

A model to induce scattered cell damage in the corneal endothelium was set up by shaking a pig cornea in a glass bottle with 0.18% NaCl. Disseminated endothelial-cell losses, whose amounts correlated with the durations of treatment, were observed in the corneas which were shaken for less than 8 min. Following organ culturing for 1 week, most of the corneas still possessed intact endothelia which means that even after the treatment the endothelium still keeps a normal regenerative ability. With this method of design, a good model is provided to study the regeneration of the corneal endothelium.

Animals↗
PubMed1989

Vacuum fixation of corneal lenticules for refractive surgery.

Using the rotating lamellar keratome, a simplified method for nonfreeze shaping of corneal tissue was developed. A set of refractive molding forms was designed for a standardized lenticule diameter. The fixation of the lenticule was achieved by a system of suction holes. A mechanical fixation ring was not required, as the total shearing force exerted by the rotating blade is neutralized even by a low suction setting. Different surface properties (polished, matt, rough) were compared, showing an influence of the surface structure on friction and thus lenticule fixation. With our optimized molding form, the lenticule is safely retained at a suction of 2.5 m H2O.

Cornea↗
PubMed1989

[Experimental studies of the correlation of morphologic endothelial cell findings and endothelial pump function].

In our experiments corneal endothelial cell morphology after Alizarin Red and Trypan Blue staining and endothelial pump function in a perfusion chamber were investigated. As a model for morphologically degenerated tissue we used corneas that had been cryopreserved with two different methods. In control groups 1) fresh, 2) one day organ cultured and 3) corneas without endothelium were evaluated. Morphologic evaluation showed degenerations (enlarged mononucleated cells, giant cells, disseminated necrotic areas) in cryopreserved corneas as compared with control groups. However, in perfusion experiments morphologically damaged tissue showed the same deswelling pattern as organ-cultured corneas. The results show that a morphologic evaluation seems to be a more precise criterion for the quality of the tissue than the investigation of the corneal pump function in a perfusion chamber.

Animals↗
PubMed1989

[Doppler sonographic findings in the central retinal artery and vein].

In a group of healthy subjects of varying ages, the flow velocities in the central retinal artery and vein were measured with a B-mode-guided pulsed duplex scanner. The first measurements were taken in the unaffected eye. The maximal systolic flow velocities ranged from 2.9 to 10 cm/s (mean 5.7 cm/s) in the central vein and from 4 to 20 cm/s (mean 9.5 cm/s) in the central artery. The correct assignment of the measuring points in the papillary region was verified by the close correlation between the flow velocity and artificially elevated intraocular pressure. After evaluating 158 clinical examinations, we try to outline the diagnostic possibilities of the method with respect to single observations in patients with ocular circulatory disturbances.

Blood Flow Velocity↗
PubMed1989

[Accommodation-convergence coupling using the stereomicroscope].

The term "instrument myopia" means an accommodative effort caused by the view into the microscope. This accommodation may be connected with the convergence position of the eye. Heterophoria should be developed if accommodation-induced convergence of the eyes does not harmonize with convergence of the ocular axes of a stereomicroscope. In 16 probands, an accommodation of 1.1 +/- 0.72 dpt and esophoria of +11.1 +/- 8.5 pdpt were measured at parallel ocular axes. The accommodation increased by 0.12 dpt/degree convergence with increasing convergence angle of the ocular axes. When the visual field was unrestricted, this line intersected the accommodation convergence line at 6.7 degrees. The esophoria decreased with increasing convergence angle and passed over to exophoria. At 8 degrees convergence, heterophoria amounted to -0.2 +/- 2.9 pdpt, and at 16 degrees exophoria was -12 +/- 9.5 pdpt. The minor degree of heterophoria and especially the very minor heterophoria at 8 degrees convergence support the view that the optimum convergence of the ocular axes is near where both accommodation convergence lines intersect.

Accommodation, Ocular↗
PubMed1989

[Glaucoma in childhood].

An overview about the classification, diagnostic and therapy of the congenital glaucomas is given. The morphological findings play an important role in the classification as well as in the diagnostic procedure. Tonometry, Sonioscopy, corneal diameter measurements, oculometry and the evaluation of the optic disc are the main diagnostic criterias. The specific normal values for newborn babies and small children are demonstrated. Up to now no satisfactory medical treatment is available for the congenital glaucomas. Goniotomy is the operation of choice. The technique of goniotomy and their modifications leeding to the cyclodialysis ab interno are described. Own longtime results of goniotomy are finally demonstrated.

Child↗