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Applanation Resonance Tonometry for Intraocular Pressure Measurement
Umeå University, Faculty of Science and Technology, Applied Physics and Electronics.
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 [en]
Physics, Resonance, applanation, tonometry, glaucoma, Goldmann, biomechanical, Intraocular, ART
Keyword [sv]
Fysik
Research subject
Physics
Identifiers
URN: urn:nbn:se:umu:diva-784ISBN: 91-7264-061-8 (print)OAI: oai:DiVA.org:umu-784DiVA: diva2:144522
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
List of papers
1. An applanation resonator sensor for measuring intraocular pressure using combined continuous force and area measurement
Open this publication in new window or tab >>An applanation resonator sensor for measuring intraocular pressure using combined continuous force and area measurement
2003 (English)In: Investigative Ophthalmology and Visual Science, ISSN 0146-0404, E-ISSN 1552-5783, Vol. 44, no 7, 3017-3024 p.Article in journal (Refereed) Published
National Category
Electrical Engineering, Electronic Engineering, Information Engineering Physical Sciences
Identifiers
urn:nbn:se:umu:diva-5125 (URN)10.1167/iovs.02-1116 (DOI)
Available from: 2006-05-03 Created: 2006-05-03 Last updated: 2017-12-14Bibliographically approved
2. Applanation resonance tonometry for intraocular pressure in humans
Open this publication in new window or tab >>Applanation resonance tonometry for intraocular pressure in humans
Show others...
2004 (English)In: Physiological Measurement, ISSN 0967-3334, E-ISSN 1361-6579, Vol. 25, no 4, 1053-1065 p.Article in journal (Refereed) Published
Abstract [en]

Glaucoma is a group of diseases associated with optic nerve damage and loss of visual field. The aetiology is not completely understood, but one of the major risk factors is elevated intraocular pressure (IOP). Reliable methods for measuring the IOP are therefore important. The aim of the study was to investigate the ability of the applanation resonance tonometry (ART) system, based on continuous force and area recording, to measure IOP in humans. Both the phase of initial indentation (IOPIndentation) and the phase when the sensor was removed (IOPRemoval) from the cornea were analysed. The Goldmann applanation tonometry (GAT) was used as reference method. The study included 24 healthy volunteers with normal IOP and 24 patients with elevated IOP. The correlation and standard deviation (SD) between IOPIndentation and IOPGAT was R = 0.92 (p < 0.001), SD = 3.6 mmHg, n = 104, and between IOPRemoval and IOPGAT R = 0.94 (p < 0.001), SD = 3.1 mmHg, n = 104. In conclusion, resonance sensor technology has made it possible to introduce a new multi-point method for measuring IOP, and the method is relevant for measuring IOP in humans. The study indicates that with further development towards elimination of position dependence, the ART has the potential to become a useful clinical instrument for IOP measurement.

Keyword
applanation resonance tonometry, glaucom, IOP
National Category
Medical and Health Sciences Ophthalmology
Research subject
Ophtalmology
Identifiers
urn:nbn:se:umu:diva-5126 (URN)10.1088/0967-3334/25/4/021 (DOI)15382841 (PubMedID)744 (Local ID)744 (Archive number)744 (OAI)
Available from: 2006-05-03 Created: 2006-05-03 Last updated: 2017-12-14Bibliographically approved
3. Symmetric sensor for applanation resonance tonometry of the eye
Open this publication in new window or tab >>Symmetric sensor for applanation resonance tonometry of the eye
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.

Keyword
Intraocular pressure, resonance sensor, applanation, eye, tonometry, glaucoma
Identifiers
urn:nbn:se:umu:diva-5127 (URN)10.1007/s11517-005-0005-1 (DOI)744 (Local ID)744 (Archive number)744 (OAI)
Available from: 2006-05-03 Created: 2006-05-03 Last updated: 2017-12-14Bibliographically approved
4. Clinical evaluation of applanation resonance tonometry: a comparison with Goldmann applanation tonometry.
Open this publication in new window or tab >>Clinical evaluation of applanation resonance tonometry: a comparison with Goldmann applanation tonometry.
2007 (English)In: Journal of glaucoma, ISSN 1057-0829, E-ISSN 1536-481X, Vol. 16, no 1, 88-93 p.Article in journal (Refereed) Published
Abstract [en]

PURPOSE: The purpose of this study was to calibrate and evaluate the precision of the new applanation resonance tonometry (ART) in a clinical study designed in accordance with the International Standard Organization's requirements. METHODS: This was a prospective, randomized, single-center study, where healthy volunteers and patients participated. A total of 153 eyes were divided into 3 groups with respect to their intraocular pressure (IOP) at screening: <16 mm Hg, 16 to 23 mm Hg, and >23 mm Hg. IOP was measured with Goldmann applanation tonometry (GAT) as reference method and by ART in both a biomicroscope (ARTBiom) and a handheld (ARTHand) setup with a 10-minutes pause between methods. The mean of 6 readings was regarded as one measurement value. RESULTS: Mean age of the subjects was 59 years (range 20 to 87 y). GAT showed a mean IOP of 20.0 mm Hg (range 8.5 to 43.5 mm Hg, n=153). The precision was 2.07 mm Hg for ARTBiom and 2.50 mm Hg for ARTHand, with a significant dependency for age as compared with GAT. Measurement order produced a decreasing IOP with a mean of 2.3 mm Hg between the first and last method. CONCLUSIONS: The precision obtained in both ARTBiom and ARTHand was within the limits set by the International Standard Organization standards for tonometers. The standardized procedure and the stability of the biomicroscope setup resulted in a slightly better precision as compared with the handheld setup. Despite a 10-minutes pause between measurements, the order was a significant factor, possibly because the patients were more apprehensive at the first measurement.

National Category
Ophthalmology
Research subject
Ophtalmology
Identifiers
urn:nbn:se:umu:diva-23729 (URN)10.1097/01.ijg.0000243468.28590.8e (DOI)17224756 (PubMedID)744 (Local ID)744 (Archive number)744 (OAI)
Available from: 2009-06-29 Created: 2009-06-29 Last updated: 2017-12-13Bibliographically approved
5. Underestimation of intraocular pressure after photorefractive keratectomy - a biomechanical analysis
Open this publication in new window or tab >>Underestimation of intraocular pressure after photorefractive keratectomy - a biomechanical analysis
Show others...
(English)Article in journal (Refereed) Submitted
Identifiers
urn:nbn:se:umu:diva-5129 (URN)
Available from: 2006-05-03 Created: 2006-05-03 Last updated: 2015-03-19Bibliographically approved

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