Biomedical subjects

S Groenhoff

Publications and source records attributed to S Groenhoff.

10 recordsLinked to original sources

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

[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

[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↗

PubMed1993

Self-tonometry under microgravity conditions.

During a space mission flown in microgravity early changes in intraocular pressure due to the fluid shift effect in microgravity were analyzed with an automatic self-tonometer. In total, 13 pressure readings per eye were obtained during the mission. The first pressure readings 16 min after reaching microgravity revealed a 92% rise in intraocular pressure compared to the daytime-correlated baseline data on earth followed by an adaptation phase lasting for several hours. Diurnal pressure profiles during the mission showed no relevant difference in altitude and amplitude.

Humans↗

PubMed1993

[Results of self-tonometry during the 1st German-Russian MIR mission 1992].

The 1st German-Russian MIR mission 1992 is one result of the agreement about technical and scientific cooperation between Germany and the former Soviet Union. Fourteen experiments have been performed during the 8-day manned space mission, one of which was called "TON": self-tonometry in mu-gravity. A total of 70 measurements of intraocular pressure (IOP) was performed in the SOJUS TM capsule as well as in the MIR space station with the automatic self-tonometer. The first pressure readings 16 min after reaching mu-gravity revealed a 92% rise in the IOP compared to the baseline data on earth followed by an adaptation phase lasting several hours. Important information about the handling of the self-tonometer in mu-gravity was obtained. Its use is also planned for the 2nd German D-2 Spacelab-Mission in March 1993.

Adult↗

PubMed1993

[Optimizing the automatic self-tonometer by an acoustic control signal and changed fixation optics].

An automatic self-tonometer must fulfill special requirements from the point of view of precision as well as user-friendliness. The sensor that applanates the cornea must be perfectly centered on the vertex in order to measure the intraocular pressure correctly. The modified version of the self-tonometer has been equipped with an acoustic control signal and a modified fixation lamp that facilitate its use. In order to analyze the effectiveness of these hardware changes, we compared the modified tonometer to the existing self-tonometer in a randomized study with 30 patients. Reference was the Draeger hand-held applanation tonometer. The results show comparable precision; however, the percentage of error measurements in the modified tonometer was considerably lower. This is a definite improvement in the development of the self-tonometer.

Adolescent↗

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

[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↗

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

[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↗