Biomedical subjects

H Kanngiesser

Publications and source records attributed to H Kanngiesser.

5 recordsLinked to original sources

PubMed2005

[Tonometry in change. From indentation and applanation to contour adaptation].

The dynamic contour tonometer (DCT) is the first and only noninvasive contact tonometer that is capable of measuring intraocular pressure (IOP) directly and continuously. The touch of the pressure-sensitive tonometer tip induces the cornea to gently assume a shape (contour) which it will naturally assume when pressure on both sides is equal. A force field establishes between tonometer tip and cornea, that corresponds exactly to IOP. A piezoresistive pressure sensor, integrated into the surface of the tonometer tip, precisely measures IOP continuously and therefore also records time-dependent modulations of IOP as "ocular pulse amplitude" (OPA). Dependence of the DCT on biomechanical properties of the cornea is substantially smaller than with traditional tonometers that applanate or indent the cornea.

Cornea↗

PubMed1997

Contact lens tonometry--application in humans.

PURPOSE: To establish a standard clinical procedure for measuring intraocular pressure (Po) with the contact lens tonometer (CLT), to demonstrate possibilities for analyzing ocular pulsation and performing ophthalmodynamometry. METHODS: A reliable histogram-based analyzing system for determining Po is used. First, the ocular pressure was registered with the CLT method and compared with the Goldmann applanation pressure, measured immediately beforehand. Second, ocular pulsation was studied by recording Po for 30 to 70 seconds, and the pulse amplitude was then analyzed. Third, an ophthalmodynamometry method during slit-lamp examination was tested. The central retinal artery was observed through the contact lens while the appositional force was elevated. A mark was set at the systolic and diastolic pressure while observing arterial pulsation (similar to the Korotkoff sounds). RESULTS: Compared with the Goldmann method measurements, Po obtained with the CLT method yielded a linear regression of r = 0.7 (right eye) and r = 0.68 (left eye), and was therefore highly significant (P < 0.0001, two-tailed). Analysis of the pulse amplitude showed great variability (range, 1 to 9 mm Hg; means, 2.9 mm Hg [right eye] and 3.0 mm Hg [left eye]). The dependence of the pulse amplitude on Po and age was shown with a correlation coefficient of r = 0.55 and r = 0.59, respectively. The difference between the right and left eye of the person was < 0.5 mm Hg. CONCLUSION: The CLT can be used during slit-lamp examination and permits tonometry during ophthalmoscopy, ocular pulsation assessment at different intraocular pressures, and ophthalmodynamometry.

Blood Pressure↗

PubMed1996

[Contact glass tonometer].

This paper present a tonometer incorporated in a contact lens, which allows simultaneous measurement of intraocular pressure and performance ophthalmoscopy. The tonometer can record the pulse curve continuously, which can give us an indication of any circulatory problem. The device is therefore expected to yield additional information useful for the diagnosis of early glaucoma. Te device has three force sensors built in, which allow continuous measurement of the force exerted on the eye surface by the contact lens. The force of the contact lens on the eye can be altered and makes the adjustment of different eye pressures possible. These induced changes of the eye pressure and their influence on the fundus can be checked. We have taken some measurements on enucleated human eyes to compare our device with a Statham tansducer in the vitreous. We found a good correlation. We are currently taking measurements in volunteers. The clinical relevance of these observations and measurements will be examined in a future study.

Calibration↗

PubMed1996

[Contact glass tonometer].

BACKGROUND: This paper presents a tonometer built into a contactlens, which allows to measure the eye-pressure and to perform ophthalmoscopy at the same time. Artificially induced changes of the eye-pressure and their influence on the visible fundus can now be checked simultaneously. The contactlens-tonometer (CGT) also is able to record continuously the pulse-curve, which can indicate any circulatory problem. So, the device is expected to give us additional diagnostic criteria of early glaucoma. Each ophthalmologyst in the field will be able to perform with this device a oculodynamometry in an easy way. By this it is possible to estimate the pressure-tolerance of the optic disk from glaucoma-patients. MEASUREMENTS: There have been taken some measurements on enucleated human eyes, comparing our device with a Statham-transducer in the vitreous. We found a good correlation. In a second step, we made measurements (65) on healthy volunteers, comparing the device with Perkins-Tonometry. RESULTS AND CONCLUSIONS: We found a correlation (R = 0.58). The error of the measurements was about +/- 3 mm Hg. Considering both, the deviation of the Perkins-Tonometer with which our results were compared, and the fact of a good correlation (R = 0.999) in the study with the enucleated human eyes, we found that the contact-lens-tonometer measures the intraocular pressure exactly. In future studies, we want to analyze the dynamic component of the measurements.

Contact Lenses↗

PubMedDate not supplied

Principles of contact lens tonometry.

We constructed a contact lens with an integrated pressure-sensing device. It is housed in a container with three force-sensing elements, each 120 degrees apart, enabling measurement of the appositional force, i.e., the force with which the instrument is held against the eye. In part 1 of the study, the lens' precision was tested against a manometric transducer in five eye bank eyes. The second part examined pressure as a factor dependent on the appositional force, and the third part of the study investigated the correct procedure for measuring baseline eye pressure, p0. The instrument described here allows investigation of three examination parameters: (a) the measurement of p0, the pressure independent of the appositional force; (b) the continuous measurement of the intraocular pressure (IOP); (c) the measurement of the IOP dependent on the appositional force, including artificial IOP elevation.

Cadaver↗