Optical measurement of the corneal oscillation for the determination of the intraocular pressure
-
Jan Osmers
,
Michael Sorg
Abstract
Motivation
Glaucoma is currently the most common irreversible cause of blindness worldwide. A significant risk factor is an individually increased intraocular pressure (IOP). A precise measurement method is needed to determine the IOP in order to support the diagnosis of the disease and to monitor the outcome of the IOP reduction as a medical intervention. A handheld device is under development with which the patient can perform self-measurements outside the clinical environment.
Method
For the measurement principle of the self-tonometer the eye is acoustically excited to oscillate, which is analyzed and attributed to the present IOP. In order to detect the corneal oscillation, an optical sensor is required which meets the demands of a compact, battery driven self-tonometer. A combination of an infrared diode and a phototransistor provides a high-resolution measurement of the corneal oscillation in the range of 10 μm–150 μm, which is compared to a reference sensor in the context of this study. By means of an angular arrangement of the emitter and the detector, the degree of reflected radiation of the cornea can be increased, allowing a measurement with a high signal-to-noise ratio.
Results
By adjusting the angle of incidence between the detector and the emitter, the signal-to-noise ratio was improved by 40 dB which now allows reasonable measurements of the corneal oscillation. For low amplitudes (10 μm) the signal-to-noise ratio is 10% higher than that of the commercial reference sensor. On the basis of amplitude variations at different IOP levels, the estimated standard uncertainty amounts to <0.5 mm Hg in the physiological pressure range with the proposed measuring approach.
Conclusion
With a compact and cost-effective approach, that suits the requirements for a handheld self-tonometer, the corneal oscillation can be detected with high temporal resolution. The cross-sensitivity of the sensor concept concerning a distance variation can be reduced by adding a distance sensor. Existing systematic influences of corneal biomechanics will be integrated in the sensor concept as a consecutive step.
Acknowledgment
The results outlined here were achieved within the project “SelTon - Selbsttonometer zur Bestimmung des intraokularen Drucks mit akustischer Schwingungsanregung”.
Author Statement
Research funding: The project was funded by the German Federal Ministry of Education and Research (BMBF, reference number 13GW0054, Funder Id: 10.13039/501100002347).
Conflict of interest: Authors state no conflict of interest.
Informed consent: Informed consent is not applicable.
Ethical approval: The conducted research is not related to either human or animals use.
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Articles in the same Issue
- Frontmatter
- Research articles
- Wireless video transmission into the MRI magnet room: implementation and evaluation at 1.5T, 3T and 7T
- Biomimetic multilayer coatings deliver gentamicin and reduce implant-related osteomyelitis in rats
- A versatile perfusion bioreactor and endothelializable photo cross-linked tubes of gelatin methacryloyl as promising tools in tissue engineering
- Comparative biomechanical evaluation of two technologically different microprocessor-controlled prosthetic knee joints in safety-relevant daily-life situations
- Non-invasive improved technique for lumbar discus hernia classification based on fuzzy logic
- Development of a wheeled walker braking device using the four-bar mechanism
- Electrically evoked wrist extensor muscle fatigue throughout repetitive motion as measured by mechanomyography and near-infrared spectroscopy
- A thermometry software tool for monitoring laser-induced interstitial thermotherapy
- Dual frequency bioelectrical impedance analysis to estimate hematocrit for prognosis of dengue fever in Indian children
- Optical measurement of the corneal oscillation for the determination of the intraocular pressure
- Does airborne ultrasound lead to activation of the auditory cortex?
