Biomedical subjects

J Draeger

Publications and source records attributed to J Draeger.

At least 37 records · Page 2Linked to original sources

PubMed1996

[Clinical calibration and in vitro evaluation of the validity of 2 microprocessor controlled tonometers].

In a randomised clinical study two new microprocessor-controlled tonometers working according to the Mackay-Marg principle (Tono-Pen and ProTon, two samples of each) and two established applanation tonometers [hand-held applanation tonometer, Draeger (HAT) and Goldmann tonometer] were compared with respect to accuracy, precision, examiner dependence and internal measurement differences (Tono-Pen I vs II, ProTon I vs II). The four tonometers were used by two examiners six times on each of 193 eyes of 100 patients of the university eye department. The same measuring procedure was performed on four cadaver eyes in situ, using a manometer system. The correlation coefficient between Tono-Pen and HAT and between ProTon and HAT was 0.9, with a high standard deviation, about +/- 3.1 mmHg. HAT gave the best results in repetitive measurements in the same eye (precision: r = 0.92, SD = +/- 1.41 mmHg). In applanation tonometers but not in Mackay-Marg tonometers measurement values depended significantly on the physician. There was a significantly higher standard deviation between Tono-Pen I and II than between ProTon I and II. Concerning in vitro calibration series on human bulbs (manometry), accuracy was high with each tonometer. The regression line of HAT is similar to that of ProTon. Tono-Pen overestimates the manometrically determined intraocular pressure. Because of their lack of precision the two new tonometers are not suitable for clinical use.

Calibration↗

PubMed1996

[Descemetocele after Excimer laser phototherapeutic keratectomy in herpes simplex virus-induced keratitis: a clinico-pathologic correlation].

BACKGROUND: The indications for phototherapeutic keratectomy in superficial and deep corneal scars in Herpes simplex virus infections are controversial. Serious incidents after PTK have as yet not been reported. PATIENTS AND METHODS: A 62-year-old patient had suffered from recurrent central herpetic keratitis since 1948 and was treated for corneal scarring for the first time in 1992 by PTK. In 1995, epithelial defects were noted and, since medical treatment was unsuccessful, repeat PTK was performed. Two weeks after the second PTK, stromal infiltration with a subsequent corneal ulcer was followed by a descemetocele and perforation. RESULTS: The recurrence of Herpes simplex keratitis was treated with systemic acyclovir, and the corneal perforation, the posterior synechiae and the complicated cataract were managed by a triple procedure à chaud (7.0 x 7.5 mm). The inflammation calmed down, and a significant improvement of vision was noted at dismissal. Histopathology of the corneal button showed no epithelial cells, endothelial cell rarefication, loss of Bowman's layer resulting from PTK, stromal edema, a descemetocele with perforation of 1.5 mm in diameter, and immunohistochemically Herpes simplex virus in the deep stroma and pre-Descemet. CONCLUSIONS: Considering the clinical data and the histopathology we conclude that repeat excimer laser phototherapeutic keratectomy of herpetic keratitis without antiviral coverage may result in complications.

Cicatrix↗

PubMed1996

[Biomechanical study of corneal stability after radial keratotomy].

BACKGROUND: Radial Keratotomy is one of the most frequent refractive surgical procedures performed worldwide. It results in considerable alterations of the corneal structure. What does this mean for the mechanical properties of the cornea? METHODS: Intraocular pressure was increased via a 180 degrees tilt. Before and during this procedure, corneal topography was measured by photokeratoscopy. We examined 36 patients after RK and 25 controls who had not undergone any surgical procedure. RESULTS: The corneal center flattened by 0.523 +/- 0.054 dpt (p < 0.01) in the RK patients and by 0.187 +/- 0.045 dpt (p < 0.05) in the control group. CONCLUSION: Even several years after radial keratotomy, corneal stability is still decreased.

Adult↗

PubMed1996

[Glaucoma and aircraft pilot fitness].

Two completely different questions arise when considering glaucoma and fitness to fly: Firstly, what is the risk for a passenger with glaucoma? Secondly, what is the flight safety risk connected with pilots suffering from glaucoma? National requirements and international standards pay little regard to this disease. This is astonishing, given that the perception of flight information in the peripheral visual field is of great importance in the cockpit. On one hand, diagnostic glaucoma examinations for pilots are mainly insufficient, and on the other, progressive visual field deficiencies may go undetected because of long intervals between examinations. Intraocular pressure may increase while flying in aircraft, e.g. in the case of negative g-load. Frequent flights at high altitudes without pressurized cabin air and with decreased oxygen supply, and therefore decreased tissue oxygen saturation, may represent a risk, especially for patients with progressive nerve fibre loss.

Aircraft↗

PubMed1995

Experimental use of space-retaining substances with extended duration: functional and morphological results.

BACKGROUND: In glaucoma surgery, e.g. cyclodialysis ab interno, to date no viscous substances have been available that stay in the cyclodialysis cleft long enough to prevent scarring. We examined the qualities of two different viscoelastic substances that stay longer in the place of instillation than hyaluronic acid. METHODS: We performed cyclodialysis ab interno in 12 eyes of six owl monkeys. The right eyes were treated with the gel with the higher molecular weight, the left eyes using the gel with the lower molecular weight. The baseline data of intraocular pressure and outflow facility were compared to the values measured postoperatively up to the 140th day. Histological examination of the eyes followed. RESULTS: There was no statistically significant difference between the two substances. The mean intraocular pressure decrease was 7.9 (+/- 2.9) mmHg in the right eyes and 4.8 (+/- 2.7) mmHg in the left eyes. The histological examination showed that the gel had remained in the cyclodialysis cleft without signs of inflammation. In contrast to other viscoelastic substances studied previously, the substances in this study performed their space-retaining function without decreasing outflow facility. CONCLUSION: Both substances are suitable means of improving the rate of success of cyclodialysis ab interno, as they remain where they are instilled long enough to prevent wound scarring in the cyclodialysis cleft.

Animals↗

PubMed1995

[Corneal reinnervation after keratomileusis in situ and keratomileusis myopica--a comparison].

BACKGROUND: In a retrospective study corneal sensitivity after keratomileusis in situ and keratomileusis myopica was measured. METHOD: 5 points on the cornea were measured with the Draeger aesthesiometer at 18 eyes after keratomileusis myopica and at 66 eyes after keratomileusis in situ. RESULTS: The ingrowth of corneal nerve fibres is delayed after keratomileusis myopica compared to keratomileusis in situ because of delayed stromal repopulation of keratocytes and disturbances of stromal metabolism due to toxic effects of the cryopreservation solution.

Adolescent↗

PubMed1995

Plasma sterilization of selected ophthalmic instruments for combined intraocular surgery.

Plasma sterilization is a nontoxic fast procedure for thermolabile and thermostable microsurgical instruments. We report data on the microbicidal effectiveness for daily routine surgical instruments like steel scissors, trephination devices, microstripper and Vitro-Cat as well as irrigation/aspiration instruments. When these instruments were cleaned from blood and saline, and when H2O2 intensifiers (adapters) were applied where necessary plasma sterilization proved to be a microbiologically safe procedure with legally adequate reduction factors of > 6 log.

Bacillus↗

PubMed1995

[Effect of corneal hydration and dehydration of donor tissue on the precision of the thickness in lamellar refractive keratoplasty].

The influence of corneal hydration on the precision of plano lamellas and on the precision of lenticles modified with a "non-freeze" technique was studied in pig eyes. Ten pig eyes were dissected with a rotating lamellar microkeratome, and the discs were measured with a mechanical pachymeter. The hydration of the discs was measured in BSS and in dextran solution. A total of 160 corneal discs with different degrees of hydration were modified with a "non-freeze" technique on concave anf convex vacuum cylinders and measured with a photokeratoscope TMS. The discs increased in thickness within 3 h becoming 1.7 times as thick in BSS and 1.2 times as thick in dextran. After refractive dissection minor modifications were achieved with higher precision than were larger corrections. However, we achieved an undercorrection after all refractive dissections. Plano-discs for refractive modification should be taken from dehydrated corneoscleral discs or from intact eyes. Owing to mechanical factors during cutting and tissue hydration undercorrection of the intended change was observed.

Animals↗

PubMed1995

[Corneal reinnervation after lamellar refractive corneal surgery].

In a retrospective study corneal sensitivity after refractive autokeratoplasty for correction of myopia was measured. Thirty-eight patients operated on for keratomileusis in situ and 18 patients for keratomileusis myopica were examined with the Draeger esthesiometer between 1 and 23 months after surgery. Three measurements points were on the refractive disc, two others on the untouched cornea. After keratomileusis myopica, the corneal reinnervation is significantly delayed compared to keratomileusis in situ. In the first group sensitivity is normal after 2 years and in the second group after 1 year. Even refraction and visual acuity depend on metabolism and reorganization of the tissue after surgery. Besides retarded cell repopulation and disturbed stromal metabolism--caused by toxic and cryopreservation effects--the dissection depth of the refractive ablation is responsible for these phenomena.

Adolescent↗

PubMed1995

[Keratomileusis with a lamellar microkeratome and the excimer laser].

In a combined prospective study with E. Arnott's department, intrastromal excimer keratomileusis on the lenticle stroma was performed in 15 eyes of 15 patients (follow-up 6 months). The primary keratectomy was performed using the lamellar automatic rotating microkeratome, followed by refractive modification by the excimer laser on the excised corneal discs. For the laser ablation, a repetition rate of 10 Hz and a fluence on the corneal plane of 180 mJ/cm2 was used. Following surgery, all treated eyes were subjected to guttae of Maxitrol q.i.d. for 12 weeks. Excimer laser intrastromal keratomileusis effectively combines corneal microsurgery and photoablation. The predictability of the refractive correction is better than with the other surgical keratomileusis techniques.

Adult↗

PubMed1995

[Results of cyclodialysis combined goniotomy in treatment of dysgenetic glaucoma].

This study was performed in order to investigate the results of "cyclodialysis ab interno," i.e., a combination of goniotomy and cyclodialysis, in patients suffering from dysgenetic glaucoma. From 1985 to 1993, 69 patients (98 eyes) underwent at least one cyclodialysis ab interno. The development of intraocular pressure was examined 2 days, 4 weeks, 1/2 year, 1 year and 3 years postoperatively after the first and last cyclodialysis ab interno. Additionally, we examined intraoperative bleeding, preoperative pressure level, previous operations, reoperations, age at manifestation, and monocular or binocular manifestation for their influence on the results. The effect the operation had on visual acuity was also examined. One year after the last cyclodialysis ab interno, the IOP was regulated in 77% of the eyes. The prognosis was better for eyes with preoperative pressure values of less than 30 mmHg than for eyes with pressure values of more than 30 mmHg. It was also clearly better when the glaucoma had become manifest at the age of more than one year. Previous operations, intraoperative bleeding, and monocular or binocular manifestation had no influence on the results. In comparison with the data available for goniotomy and trabeculotomy, cyclodialysis ab interno shows a tendency for better results.

Adolescent↗

PubMed1995

Self-tonometry under microgravity conditions.

Microgravity leads to a "fluid shift" towards the upper parts of the body and, therefore, to a rise of the intraocular pressure. Parabolic flights have also demonstrated some rise of the intraocular pressure. During the first German Spacelab mission D1, changes of the intraocular pressure were investigated for the first time in space. The first pressure readings were obtained 44 min after entering microgravity and showed a pressure rise of 20 to 25% compared to the baseline data. To get earlier measurements in microgravity a fully automatic self-tonometer was developed which functioned independent of position and microgravity. It was used during an 8-d manned space mission in March 1992. Measurements of the intraocular pressure have been performed 16 min after reaching microgravity. The pressure readings revealed a 92% rise of the intraocular pressure compared to the daytime-correlated baseline data on Earth.

Fluid Shifts↗

PubMed1994

[Physical and aerodynamic airflow relations of the air stream of the Micro-Air aesthesiometer].

BACKGROUND: In an experimental study we examined the aerodynamical airstreamprofile of a new airstream aesthesiometer. With this instrument it is possible to measure corneal sensitivity without touching the cornea. METHOD: A constant hotwire-anemometer was used to measure the 0.5 s air impulse in different distances. The corneal topographic sensitivity was measured at 45 probands, age 20 to 80. RESULTS: The investigations show that the laminar air stream within the 0.2 mm wide nozzle changes after withdrawal, in regards to stream profile, jet width and speed. The parabolashaped stream profile passes over through the air matrix and changes into a bell-shaped profile. The stream properties of the circular free system imply that the air stream in a 4 mm distance is nearly half as wide and double as high or fast in comparison to an 8 mm distance. The corneal sensitivity measured with the CMA showed in comparison to the Draeger aesthesiometer a lower sensitivity than in the periphery. CONCLUSION: A clinical use for measuring corneal sensitivity with the CMA can not be recommended.

Adult↗

PubMed1994

[Corneal reinnervation after lamellar keratoplasty in comparison with epikeratophakia and photorefractive keratectomy].

Corneal sensitivity was examined with the Draeger aesthesiometer in 8 patients after lamellar keratoplasty, 7 patients after epikeratophakia and 82 patients after photorefractive keratectomy. We examined 9 different points in each cornea. The corneal sensitivity of patients after lamellar keratoplasty was normal 1 year after operation. A correlation with the depth of the lamellar dissection was demonstrated. Patients with lamellar keratoplasty with pterygium showed a sensitivity decrease in the nasal parts of the lenticule even after one year. Three years after epikeratophakia the corneal center was still not sensitive. After photorefractive keratectomy of more than 10 D, corneal hyposensitivity was shown even 2 years after operation.

Adult↗

PubMed1994

[Measuring corneal sensitivity with the air aesthesiometer in comparison with the Draeger electromagnetic air aesthesiometer].

A new air aesthesiometer developed by S. Weinstein was tested with an anemometer device. It could be shown that the air stream is not linear. The normal sensitivity threshold pattern was measured in 271 probands varying in age from 10 to 98 years. In a comparative study we measured the corneal sensitivity of 20 patients after penetrating keratoplasty with the air aesthesiometer and the Draeger electromechanical aesthesiometer. Because of the aerodynamic broadening of the airstream it was not possible to measure corneal sensitivity at the transplant periphery or host cornea with the new device, while we could demonstrate corneal nerve fibre degeneration at the host cornea or regeneration of the transplant with the electromechanical aesthesiometer.

Adolescent↗

PubMed1994

[Self tonometry during the German 1993 Spacelab D2 mission].

Microgravity during space missions leads to a fluid shift from the lower to the upper parts of the body that also affects the intraocular pressure. In the early phase after reaching microgravity there is an intraocular pressure peak. In order to analyse the potential health risks for astronauts, a self-tonometer was developed to examine the early phase of microgravity. During the German-Russian MIR mission the equipment was tested for the first time in space. As one result we found an initial pressure increase of 92% compared to the baseline data values. In order to obtain more detailed information on the intraocular pressure alterations in space, similar equipment was used during the 10-day German Spacelab D2 mission. Two German scientists and one American astronaut obtained self-tonometric pressure profiles on 6 mission days (44 pressure values determined out of 144 measurements). The initial peak values 15 min after entering microgravity revealed pressure increase of 114% compared to the baseline data (average pressure: right eye 10.0 mmHg, left eye 9.9 mmHg; peak values: right eye 22.6 mmHg, left eye 22.2 mmHg). Pressure values exceeding the baseline data by more than 50% were registered up to the 3rd mission day. As to circadian rhythm, there was no difference between inflight data and baseline data before and after the mission.

Adult↗

PubMed1994

[Evaluation of current guidelines for flying capacity and internationally proposed revisions].

Despite several modifications of medical requirements for German flight personnel, these requirements have often been criticized by ophthalmologists because of their margins of interpretation. In many controversial cases regarding pilot licences, the final decision has to be made by the national aeromedical review board. The progress in ophthalmologic microsurgery, e.g. intraocular lens implantation and refractive surgery, has led to a certain insecurity among surgeons as to how to deal with these developments within the requirements. Besides, new cockpit designs with multiple colour displays have changed the demands on the pilot's visual system, especially with regard to colour perception. New European requirements which will probably become effective in 1994 are compared to the existing German standards.

Aircraft↗

PubMed1994

[Clarity of flight information in the cockpit of the new aircraft generation].

Fundamental changes of cockpit design in recent years, especially the transition from analogue to digital flight information systems and the use of colour-coded displays, lead to new demands on the visual system of the pilot. Twenty experienced pilots each participated in four 15-min sessions with a simulator program in the new Airbus 340 Simulator of the Technical University of Berlin. The pilots were confronted with various flight situations and events. The simulation program was carried out with visual acuity of 1.0 or better, with acuity reduced to 0.5 and with red and green filters. The time between the display of information and the pilot's reaction was determined. The probands were classified into two groups according to their age (< or = 45 years, > or = 45 years). In both age groups a significant difference was found only with green filters. There was no difference with reduced visual acuity or with red filters, and no differences were seen between the two age groups.

Adult↗