Biomedical subjects

K Ehrmann

Publications and source records attributed to K Ehrmann.

8 recordsLinked to original sources

PubMed2006

Lower eyelid tensometry in younger and older normal subjects.

PURPOSE: This study aimed to establish normative and repeatability data for lower eyelid tensometry (LET) using a newly developed eyelid tensometer. METHODS: In this prospective consecutive observational case series, 32 normal adult subjects, comprising 12 younger (aged 29+/-5 years, 6M:6F) and 20 older subjects (aged 74+/-6 years, 10M:10F), underwent LET. In the younger group, LET was measured for postero-anterior (PA), nasal and temporal displacement. Duplicate measurements were taken and these were repeated on a separate occasion. Associations between repeated measurements and between right and left eyes were determined and the coefficient of repeatability for PA measurements was estimated. Differences in LET between males and females were determined using ANOVA. Only PA tensions, with duplicate measurements, were assessed in the older group, and age effects were determined. RESULTS: Mean temporal tension in the younger group was 7.8+/-2.9 mN (milliNewtons)/mm, while nasal tension was 13.0+/-4.6 mN/mm and PA tension was 11.2+/-5.3 mN/mm. There was a good correlation between interoccasion PA measurements (r=0.82-0.84, P<0.005) and between the right and left eyes (r=0.48, P<0.005). The coefficient of repeatability for PA tension was 1.8 mN/mm. In the younger group, overall eyelid tension (for all directions) for males was significantly higher than for females (ANOVA, P=0.03). For measurements in older subjects on a single occasion, PA tension was 11.1+/-3.5 mN/mm and in younger subjects 12.8+/-4.2 mN/mm (P=0.22). CONCLUSIONS: LET is rapid, repeatable, feasible, and acceptable. PA tension was the most repeatable measurement. Younger males had higher eyelid tension than females, and there was no significant reduction in PA tension with age.

Adult↗

PubMed2005

Sample patterning on NMR surface microcoils.

Aligned microcontact printing for patterning the sample in areas of homogeneous RF-field on the highly sensitive surface of planar NMR microprobes is presented. We experimentally demonstrate that sample patterning allows drastic improvement of the spin excitation uniformity. The NMR microprobes are designed for cell analysis and characterized using lipid vesicles as cell substitutes. Lipid vesicles are advantageous as composition and concentration of the confined solution are precisely controlled and because of their similarity to living cells. Using aligned microcontact printing, a monolayer of lipid vesicles is immobilized on the surface of the planar NMR microprobe in a patterned way. 1H NMR spectra and CPMG spin echoes of sucrose solution confined within the lipid vesicles are successfully recorded. Nutation curves of the sample structured in different patterns demonstrate the impact of patterning on the spin excitation uniformity. The total detection volumes are between 1 and 2 nL and derived with help of a theoretic model based on 3D finite element simulation. This model predicts the signal-to-noise ratio and the progression of the nutation curves.

Avidin↗

PubMed2005

[Results of two nationwide "smoke-free" campaigns].

BACKGROUND: "Rauchfrei" -- the German part of the international contest "Quit and Win"-- is the biggest smoking cessation campaign in Germany. Already in the year 2000 24,925 smokers participated. A total of 90,458 adolescents and adults participated in "Rauchfrei 2002", that means about 0.5 % of all German smokers. OBJECTIVE: Main aim of the quit smoking campaign is to motivate as many smokers as possible to stop smoking for at least four-weeks and herewith to achieve a stop of the tobacco consumption in the long run. In this context the continuous 4-weeks and 12-months abstinence rates of the participants serve as indicators for success. METHODS: A survey with the adult participants aged 18 and older was carried out one year after each campaign. The samples were drawn randomly from all 10 German postal zip code-areas. A response rate of over 60 % in both surveys resulted in a sample size of n = 651 (2000) and n = 996 (2002). RESULTS: By the end of "Quit and Win 2000" (2002) 72 % (69 %) of the participants were smoke-free; 12 months after the campaign 30 % (22 %) of the participants were continuously smoke-free. Overall, men were more successful than women, and participants with a lower education were as successful as participants with a higher school education. Substantially more participants, who had received support from either family members, friends or colleagues, had abstinence rates above the average. CONCLUSION: "Rauchfrei" was successfully implemented in Germany and contributed to draw attention to the risks of smoking nationwide.

Age Distribution↗

PubMed2004

Corneal and conjunctival sensitivity to air stimuli.

AIMS: To determine the repeatability of ocular surface sensitivity to mechanical stimulation using air stimuli and the effect of contact lens (CL) wear on sensitivity. METHODS: Repeatability: 14 subjects (24-39 years) participated. Mechanical sensitivity to warmed (34 degrees C) and ambient (20 degrees C) air was measured for the central cornea (CC), inferior cornea (IC), and inferior conjunctiva (ICON). Measurements were taken on 12 days; six morning and six afternoon measurements. Differences between sites, time of day, and stimulus temperature were evaluated. CL wear: 10 subjects (22-30 years) participated. Measurements were taken at the same time of day, either following no wear, wear of a CL of oxygen permeability [Dk] of 28 x 10(-9) [cm/s][ml O(2)/ml mm Hg] or wear of a CL of Dk 140 x 10(-9) [cm/s][ml O(2)/ml mm Hg]. Differences between sites and wear conditions were evaluated. RESULTS: Repeatability: Sensitivity varied between sites (p<0.01), time of day (p<0.05), and stimulus temperatures (p<0.01). There were no significant differences between days. Mean thresholds for eye temperature stimuli were; CC 64.4 (SD 28.6) ml/min; IC 84.6 (40.0) ml/min; ICON 120.6 (40.4) ml/min and for ambient temperature stimuli were CC 53.9 (16.0) ml/min, IC 59.0 (20.0) ml/min; ICON 72.6 (43.7) ml/min. CL wear: Sensitivity varied between sites and wear conditions (p<0.05). Conjunctival sensitivity was increased after wear of highly oxygen permeable CLs but unaffected by wear of low oxygen permeable CLs. CONCLUSIONS: The prototype gas aesthesiometer is able to repeatably measure ocular surface sensitivity and measurements are consistent with previously reported techniques.

Adult↗

PubMed2003

Planar microcoil-based microfluidic NMR probes.

Microfabricated small-volume NMR probes consisting of electroplated planar microcoils integrated on a glass substrate with etched microfluidic channels are fabricated and tested. 1H NMR spectra are acquired at 300 MHz with three different probes having observed sample volumes of respectively 30, 120, and 470 nL. The achieved sensitivity enables acquisition of an 1H spectrum of 160 microg sucrose in D2O, corresponding to a proof-of-concept for on-chip NMR spectroscopy. Increase of mass-sensitivity with coil diameter reduction is demonstrated experimentally for planar microcoils. Models that enable quantitative prediction of the signal-to-noise ratio and of the influence of microfluidic channel geometry on spectral resolution are presented and successfully compared to the experimental data. The main factor presently limiting sensitivity for high-resolution applications is identified as being probe-induced static magnetic field distortions. Finally, based on the presented model and measured data, future performance of planar microcoil-based microfluidic NMR probes is extrapolated and discussed.

Electronics↗

PubMed2001

A novel instrument to quantify the tension of upper and lower eyelids.

An instrument was developed for the objective measurement of passive lid tension of the upper and lower eyelid. Eyelid tension is defined as the first derivative of the force over elongation function. Lid tension was determined by gripping the eyelid at the eyelashes and displacing the lid while measuring the force exerted by the eyelid. Two motorised spindles provided motion control of the gripper in anterior/posterior and nasal/temporal directions. Each axis was fitted with a sensitive force transducer to record the force while stretching and relaxing the eyelid. Motion control, data collection and data analysis were computer controlled, with various user-selectable options for measurement speed, direction and end-of-measurement conditions. Calibration of the instrument reduced the maximum error of the recorded forces to +/- 10 mN. Repeatability for on-eye measurements was verified by multiple measurements on the same eye under identical conditions. Preliminary results from a pilot study, investigating differences between Asian and Caucasian lid tension showed no statistically significant difference between the two groups.

Journal Article↗

PubMed2001

Lens prism in RGP manufacturing and its effect on edge quality.

Unwanted prism in lathe cut RGP lenses is most frequently caused by misalignment when re-blocking the button for cutting the front surface. The geometrical relationships in three types of alignment errors and the resulting variations in edge thickness were mathematically analysed and experimentally confirmed. The edge thickness variations in a prismatic lens along the circumference follow a cosine function. For a typical tri-curve lens design, an eccentric offset 30 microm between the front and the back surface can lead to a difference in edge thickness of more than 50 microm Edge thickness variations are greatest for high power minus lenses with prominent lenticulation. The polished edge shape is significantly compromised by inconsistent edge thickness. Typically, the thinner side has a sharp and pointed edge, while the thicker side is blunt.

Journal Article↗

PubMed1999

A novel method to quantify the edge contour of RGP contact lenses.

A new method of accurate profile measurement of rigid gas permeable lenses and edges is described. A purpose built optical profilometer non-destructively scans complete cross-sections in several meridians of any rigid lens. The accuracy of the instrument was verified to be better than +/-2.5 microm. The profile data are obtained and stored in digital format for further analysis. The seven most commonly used edge features were defined by means of mathematical algorithms to extract unique numerical values for these parameters from the measured profiles. Applications of the new edge quantification method in clinical contact lens research and manufacturing quality control are shown.

Journal Article↗