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Symmetric sensor for applanation resonance tonometry of the eye
Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).ORCID iD: 0000-0003-2055-576X
Umeå University, Faculty of Medicine, Department of Clinical Sciences, Ophthalmology.
Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
Umeå University, Faculty of Medicine, Department of Radiation Sciences. Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
2006 (English)In: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 44, no 1-2, 54-60 p.Article in journal (Refereed) Published
Abstract [en]

Applanation resonance tonometry (ART) has been shown in a number of studies to be useful for measuring intraocular pressure (IOP). Data from in vitro laboratory bench testing, where the sensor was carefully centralised onto the cornea, has been very consistent with good precision in the determination of IOP. However, in a clinical study the unavoidable off-centre placement of the sensor against the cornea resulted in a reduced precision. The aim of this study was to evaluate a new design of the sensor with a symmetric sensor probe and a contact piece with a larger diameter. Two in vitro porcine eye experimental set-ups were used. One bench-based for examining position dependence and one biomicroscope-based set-up, simulating a clinical setting, for evaluating IOP(ART) precision at seven different pressure levels (1040 mmHg), set by connecting a saline column to the vitreous chamber. The reference IOP was recorded using a pressure transducer. There was no significant difference between four positions 1 mm off centre and the one centre position. The precision of the ART as compared with the reference pressure was +/- 1.03 mmHg (SD, n = 42). The design improvement has enhanced the precision of the ART in the biomicroscope set-up to be in parity with bench test results from a set-up using perfect positioning. This indicates that off-centre positioning was no longer a major contributor to the deviations in measured IOP. The precision was well within the limits set by ISO standard for eye tonometers. Therefore, a larger in vivo study on human eyes with the ART should be performed.

Place, publisher, year, edition, pages
2006. Vol. 44, no 1-2, 54-60 p.
Keyword [en]
Intraocular pressure, resonance sensor, applanation, eye, tonometry, glaucoma
Identifiers
URN: urn:nbn:se:umu:diva-5127DOI: 10.1007/s11517-005-0005-1Local ID: 744OAI: oai:DiVA.org:umu-5127DiVA: diva2:144519
Available from: 2006-05-03 Created: 2006-05-03 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Applanation Resonance Tonometry for Intraocular Pressure Measurement
Open this publication in new window or tab >>Applanation Resonance Tonometry for Intraocular Pressure Measurement
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Elevated intraocular pressure (IOP) is one of the major risk factors for glaucoma. Since glaucoma is a leading cause of blindness, reliable methods for measuring the IOP are important. This doctoral dissertation presents a new method, applanation resonance tonometry (ART), for measurement of IOP. The method is based on resonance sensor technology combined with the novel multipoint analysis of continuously sampled data of both contact force and contact area. The ART was evaluated in in vitro porcine-eye studies as well as in clinic on both healthy volunteers and patients.

A new symmetric probe with a larger sensor tip and improved aligning light was developed and evaluated in vitro. It showed that the error from off-centring was highly reduced. The new ART probe, used as a biomicroscope device (ARTBiom) and as a handheld device (ARTHand), was further evaluated in a clinical study designed in accordance with the International Standard Organisation’s (ISO) requirement. Both the ARTBiom and the ARTHand met the precision set by the requirements.

Laser surgery is a common way to correct vision. The biomechanical effect of photorefractive keratectomy (PRK) on IOP measurements was evaluated using Goldmann applanation tonometry (GAT) and ART in an in vitro study. Both methods were affected, but to a different extent. The flat contact probe of GAT, as compared with the convex tip of ART, and single point vs. multipoint approach, provide explanation to the ART advantage regarding measurement error of IOP after PRK.

In conclusion, resonance sensor technology has made it possible to introduce a new multipoint method for measuring IOP, and the method is relevant for measuring IOP in humans. It may be possible to reduce errors in the clinical measurement of IOP with this new method, especially after corneal surgery. The ART has the potential to become a useful clinical instrument for IOP measurement.

Place, publisher, year, edition, pages
Umeå: Tillämpad fysik och elektronik, 2006. 63 p.
Series
Resonance Sensor Lab, ISSN 1653-6789 ; 1
Keyword
Physics, Resonance, applanation, tonometry, glaucoma, Goldmann, biomechanical, Intraocular, ART, Fysik
Research subject
Physics
Identifiers
urn:nbn:se:umu:diva-784 (URN)91-7264-061-8 (ISBN)
Public defence
2006-05-24, Sal B, 9tr., Tandläkarhögskolan, Norrlands Universitetssjukhus, Umeå, 13:00 (English)
Opponent
Supervisors
Available from: 2006-05-03 Created: 2006-05-03 Last updated: 2010-02-01Bibliographically approved

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Hallberg, PerLindén, ChristinaBäcklund, TomasEklund, Anders
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Department of Applied Physics and ElectronicsCentre for Biomedical Engineering and Physics (CMTF)OphthalmologyDepartment of Radiation Sciences
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