Results of First In Vivo Trial of an Acoustic Self-Tonometer
Ágnes Patzkó2020, Translational Vision Science & Technology
Sign up for access to the world's latest research
checkGet notified about relevant papers
checkSave papers to use in your research
checkJoin the discussion with peers
checkTrack your impact
Abstract
Glaucoma is the world's most common cause of irreversible blindness, which makes early diagnosis, with the goal of preserving vision, essential. The current medical intervention is to reduce intraocular pressure (IOP) to slow down progression of the disease. The main goal of this study was to test a novel handheld acoustic self-tonometer on humans. Methods: A sound pressure pulse generated by a loudspeaker causes the eye to vibrate. A pressure chamber is placed on the human orbit to form a coupled system comprised of the patient's eye, the enclosed air, and the loudspeaker. A displacement sensor in front of the loudspeaker membrane allows the dynamic behavior of the entire system to be detected. Results: For this clinical trial series, a prototype of the acoustic self-tonometer principle was applied. The resulting membrane oscillation data showed sensitivity of patient IOP, but direct allocation of the measured damping and frequency to the IOP was not significant. For this reason, an artificial neural network was used to find relationships among the subjects' biometric eye parameters in combination with the self-tonometer data for the IOP reference. An expanded measurement uncertainty (k p = 2) equal to 6.53 mm Hg was determined for the self-tonometer in a Bland-Altman analysis using Goldmann applanation tonometer reference measurements. Conclusions: The usability and success rate of producing valid measurement values with the device during self-measurements by test subjects was nearly 92%. The crosssensitivities observed require compensation in a possible redesign phase to reduce the measurement uncertainty by at least 25% to the maximum of 5 mm Hg required to seek medical device approval. Translational Relevance: Building on successful laboratory experiments with pig eyes, this article reports the results of testing the acoustic tonometer on humans.
Related papers
The influence of intraocular pressure on the damping of a coupled speaker–air–eye system
Journal of Sensors and Sensor Systems, 2018
Although glaucoma is currently the world's most common cause of irreversible blindness, there is no curative therapy available to date. The major risk factor that can be influenced in order to stop disease progression is the eye pressure (IOP). Therefore early diagnosis of an altered IOP is essential for the goal of preserving vision. A novel IOP measurement principle for a handheld noncontact self-tonometer shall be validated. The measurement principle uses a pressure pulse generated by a loudspeaker to cause vibrations of the eye. In order to reach the required sound pressure, a closed pressure chamber is placed on the human orbit. With a microphone and a displacement sensor the dynamic behavior of the entire system is detected. In this article the abovementioned principle is being analyzed on porcine eyes under laboratory conditions. The combination of the loudspeaker, the pressure chamber, and the eye to be measured can be described as a coupled spring-mass-damper system. It is demonstrated for enucleated porcine eyes that a defined IOP variation leads to a change in the system's damping ratio. Considering only stochastic deviations, the derived standard uncertainty for the determination of the IOP amounts to < 1 mmHg in the physiological range. The in vitro measurements on porcine eyes help the understanding of the underlying physics and demand for further research on the influence of biometric parameters on eye vibrations. However, the laboratory results provide the basis for a gentle noncontact tonometry method with great applicational prospects. Data is currently being collected on human subjects in a clinical trial, to corroborate the measurement principle in vivo.
Comparison of three methods of tonometry in normal subjects: Goldmann applanation tonometer, non-contact airpuff tonometer, and Tono-Pen XL
Clinical Ophthalmology, 2014
We aimed to compare intraocular pressure (IOP) measurements via three different tonometers: the Goldmann applanation tonometer (GAT), the Tono-Pen ® XL (TPXL), and a non-contact airpuff tonometer (NCT). Methods: This was a cross-sectional study of 200 eyes from 200 patients. Right eyes of all patients were included in this study. IOP was measured via GAT, NCT, and TPXL by three physicians. Each physician used one of the tonometers. Measurements via the three devices were compared. Results: The mean IOP was 15.5±2.2 mmHg (range 10-22) with the GAT, 16.1±3.0 (range 9-25) with the TPXL, and 16.1±2.8 (range 10-26) with the NCT. Bland-Altman analysis showed that the mean difference between measurements from the NCT and the GAT was 0.6±2.3 mmHg. The mean difference between the TPXL and GAT measurements was 0.7±2.5 mmHg. The mean difference between the NCT and TPXL measurements was -0.02±3.0 mmHg. There was no significant difference between the groups according to a one-way analysis of variance (ANOVA) test. P-values were 0.998 for NCT-TPXL, 0.067 for NCT-GAT, and 0.059 for TPXL-GAT. Conclusion: The NCT and TPXL provide IOP measurements comparable to those of the gold standard GAT in normotensive eyes.
Developments and Progress in Non-contact Eye Tonometer Calibration
Measurement Science Review
This paper focuses on the problematic of intraocular pressure (IOP) measurements, performed by non-invasive methods. More specifically, the devices that are connected with the presented finding are non-contact tonometers that use concentrated air stream and optical sensors to determine the IOP within a human’s eye. The paper analyzes various influential factors that have an effect on the determination of the IOP values originating from the patients themselves and from the non-contact tonometer devices. The paper furthermore elaborates on the lack of independent methods of calibration and control of these devices. In order to fill this gap a measurement standard device that is capable of calibrating and testing these devices with traceability to the basic SI unit is presented. A detailed characterization and the determination of the expected uncertainty of the device are provided. By introducing an independent and traceable calibration method and control of non-contact tonometers int...
Applanation resonance tonometry for intraocular pressure in humans
Physiological Measurement, 2004
Doubt is the beginning of wisdom. (René Descartes) 4 5
The Icare HOME (TA022) Study Performance of an Intraocular Pressure Measuring Device for Self-Tonometry by Glaucoma Patients
Ophthalmology, 2016
Purpose: To evaluate the Icare HOME (TA022) device (Icare Oy, Vanda, Finland) for use by glaucoma patients for self-tonometry. Design: Prospective performance evaluation of a medical device. Participants: One hundred eighty-nine participants with glaucoma or suspected glaucoma were recruited from the Wilmer Eye Institute, Baltimore, Maryland, between July 2014 and April 2015. Methods: Participants had standardized training and had to be able use the Icare HOME device independently. Subjects also had to be able to obtain the first intraocular pressure (IOP) measurement within 5 mmHg of Goldmann applanation tonometry (GAT). Those certified obtained 3 IOP measures using the HOME device, and these were compared with Icare TA01i and GAT IOP measurements. Main Outcome Measures: The agreement between Icare HOME and reference tonometers was used to assess precision. The intraclass correlation coefficient was used to assess within-patient reliability for the HOME device. Results: Eighteen of 189 recruited patients were ineligible to take part in the study. Forty-four of 171 patients (25.7%) started but failed to complete the study: 7 stopped because of time concerns, 10 of 171 patients (6%) stopped because of difficulty using the device during certification, and 27 of 171 patients (16%) failed to be certified based on IOP. The HOME and GAT measurements agreed within 5 mmHg in 116 of 127 participants (91.3%); 2 participants (1.6%) had a difference of more than 7 mmHg. The mean difference between the Icare HOME and GAT measurements was À0.33 mmHg (standard deviation, 3.11 mmHg). The overall intraclass correlation coefficient for the HOME device was 0.92 (95% confidence interval, 0.89e0.95). Conclusions: Not all participants could learn how to use the Icare HOME device, but for those who could, most were able to obtain measurements similar to those obtained by GAT. The Icare HOME device is safe and reliable for self-tonometry, but nearly 1 in 6 individuals may fail to certify in use of the device based on large differences in IOP when comparing GAT with the Icare HOME measurements. The device has the potential to address an unmet need by providing more frequent IOP measurements in a patient's day to day life. Ophthalmology 2016;123:1675-1684 ª 2016 by the American Academy of Ophthalmology. Intraocular pressure (IOP) is a key factor in the development and progression of glaucoma, and all treatments for glau-coma are intended to lower IOP. Despite this, most patients undergo IOP measurement only once every 6 months or more. Since most IOP measurements are performed using Goldmann applanation tonometry (GAT), more frequent measurement generally is deferred because of impracticality and the cost of time and resources. The Food and Drug Administration-approved rebound Icare TA01i tonometer (Icare Oy, Vanda, Finland) has proved useful in routine clinical settings with the advantages of being easy to use and not requiring topical anesthesia. However, it is used by trained personal and is not designed for self-use. The Icare HOME tonometer (TA022; Icare Oy), which is not approved by the Food and Drug Administration , is a rebound tonometer that has been developed for home use and may allow for better monitoring of variations in IOP through self-tonometry at home, as well as electronic documentation of these measurements. This study aimed to determine the agreement between self-measured IOP using the Icare HOME tonometer and GAT, as well as between the Icare HOME and the Icare TA01i tonometers. The study further aimed to record and analyze record and analyze patients' self-reported comfort while using the device, as well as clinical observations of corneal epithelial defects or other adverse events when using the Icare HOME.
The evaluation of tonometry and self-tonometry with Ocuton tonometers
Medical science monitor : international medical journal of experimental and clinical research, 2003
The purpose of the present study was to evaluate the clinical applicability of the Ocuton-A and Ocuton-S applanation tonometers, and to compare their use and accuracy parameters to those of Goldmann applanation tonometry (GAT). In the first study, intraocular pressure (IOP) was measured with an Ocuton-A tonometer, followed by another measurement using GAT in 15 subjects (30 eyes). Ocuton-tonometry was performed on three occasions separated by three-minute intervals. In Study 2 the impact of increased patient familiarity on measurement accuracy using the self-tonometer was investigated in 5 subjects (10 eyes) by comparing two consecutive series of five Ocuton-S measurements. In Study 3 nine trained volunteers measured their own IOP with an Ocuton-S self-tonometer after GAT and Ocuton-A measurements by an experienced investigator. Study 1 showed that the measured IOP value was significantly higher using the Ocuton-A tonometer, compared to values obtained using GAT. In Study 2 we found...
Intraocular pressure measurement precision with the Goldmann applanation, dynamic contour, and ocular response analyzer tonometers
Ophthalmology, 2010
Objective: To examine the repeatability and reproducibility of intraocular pressure (IOP) measurements obtained with the Goldmann applanation tonometer (GAT), the Pascal dynamic contour tonometer (DCT; Swiss Microtechnology AG, Port, Switzerland), and the Reichert Ocular Response Analyzer (ORA; Reichert Ophthalmic Instruments, Buffalo, NY). A secondary objective was to assess agreement between the devices.
The validity of a digital eyelid tonometer (TGDc-01) and its comparison with Goldmann applanation tonometry - a pilot study
Ophthalmic and Physiological Optics, 2005
Purpose: To determine the intra-and inter-examiner repeatability of a new eyelid tonometer, and its agreement with Goldmann applanation tonometry (GAT). Materials and methods: Forty normal subjects were recruited and their intraocular pressure was measured by two examiners using the eyelid tonometer. Examiner 1 carried out the first set of measurement, followed by examiner 2, and then examiner 1 again. Finally, a third examiner was responsible for GAT measurement. Five readings were obtained from the eyelid tonometer by each examiner each time and were masked, and three readings were obtained from GAT. The mean readings from the eyelid tonometer and GAT were used for analysis. Results: The intra-examiner repeatability for the eyelid tonometer was better (around ±5 mmHg 95% of the cases) than the inter-examiner repeatability (around ±8 mmHg 95% of the cases). The mean difference between the eyelid tonometer and GAT was small from examiner 1 (<0.5 mmHg). However, the limits of agreement were greater than the clinically acceptable level of ±3 mmHg. Examiner 2 gave an even greater difference from GAT. Conclusions: Similar to other recent studies, we have found that this eyelid tonometer does not provide good agreement with GAT. Different examiners could position the instrument differently and this eyelid tonometer is suggested for screening purposes only.
Self-tonometry in Glaucoma Management—Past, Present and Future
Survey of Ophthalmology, 2009
Glaucoma is the leading cause of irreversible blindness in the world. Diagnosis and management of glaucoma is significantly associated with intraocular pressure, but contemporary officebased measurements are not sufficient to discover diurnal changes and spikes, nor do they demonstrate the effect of medication and compliance. Patient-directed self-tonometry can be taken throughout the day and is therefore the subject of much discussion and research. In this article we review the history of self-tonometry devices and present technologies for the future.
A new electronic tonometer for ocular epipalpebral measurements
IEEE transactions on bio-medical engineering, 2008
A new electronic tonometer is presented in this paper. This is an electromechanical device that has been designed to establish, by means of a fully automatic process, an approximate value of the intraocular pressure (IOP) without the need to be handled by an ophthalmologist. It can be applied on the closed eyelid with no danger for the patient in an easy and simple way. These have been the main prerequisites for the proposed tonometer in order for it to be used in the future in the same way as domestic clinical thermometers are used nowadays. The main benefits obtained with this measurement is a much earlier warning in cases where incipient glaucoma is already carving its silent way to an unexpected future blindness. The tonometer can also be used and has been employed as a research instrument, placed either on the eyelid or on the cornea, and a substantial flow of data on how IOP evolves is obtainable by computerized means. The tonometer is based on a microcontroller device, which is the electronic core of the equipment that manages the user interface, runs the complete test, and shows the final results. This paper describes the design in a stage previous to the "domestic tonometer": a laboratory prototype to obtain physical properties of the eye under a variable static, radial, and epipalpebral force.
Tonometry – Past, Present and Future
Glaucoma - Current Clinical and Research Aspects, 2011
Comparison of intraocular pressure as measured by three different non-contact tonometers and goldmann applanation tonometer for non-glaucomatous subjects
BMC ophthalmology, 2017
To compare the measurement of intraocular pressure (IOP) among the three different non-contact tonometers (NCT) and the Goldmann applanation tonometer (GAT) for non-glaucomatous subjects. In 52 eyes of 52 non-glaucomatous subjects, IOP was measured sequentially with the Canon TX-20P, the Nidek NT-530P, the Topcon CT-1P, and the GAT at the same time. We evaluated the IOP-measurement agreement among the tonometers as well as the factors affecting the measurements. A significant positive correlation was shown between the IOP values obtained with GAT and each NCT. The Canon TX-20P showed statistically the most significant agreement with the GAT (ICC 0.906, 95% CI 0.837-0.946). In an analysis of the Bland-Altman plots, the Canon TX-20P also showed the largest mean bias (1.38 mmHg) but the narrowest limits of agreement (LoA) (95% LoA; ± 3.43 mmHg). The Topcon CT-1P showed the smallest mean bias (0.48 mmHg) but the widest LoA (95% LoA; ± 4.16 mmHg). The Topcon CT-1P and Nidek NT-530P both ...
Clinical performance of the Reichert AT550: a new non-contact tonometer
Ophthalmic and Physiological Optics, 2002
The aim of the present study was to assess the level of accuracy for measurements of intra-ocular pressure (IOP) obtained with a new non-contact tonometer (NCT) the Reichert AT550 Ò. Measurements were compared against those obtained with the Reichert Xpert Plus, Goldmann applanation tonometer and Perkins tonometer. Thirty-five university students were assessed with the four tonometers in a randomised order, with non-contact tonometry performed first. Each of the four measurement devices had its own trained clinical observer. Plots of differences of IOP as a function of the mean for each pair of instruments were obtained. No statistically significant differences were found when comparing the AT550 Ò NCT with contact applanation tonometry (AT) (p > 0.05), displaying the closest level of agreement (as represented by the lowest mean difference and the narrowest confidence interval) with the Goldmann tonometer (limits of agreement, 0.12 ± 2.17). In conclusion, readings of IOP with the AT550 Ò NCT are clinically comparable with those obtained with Goldmann tonometry in a population with IOP within the normal range.
Trans-scleral tactile tonometry: An instrumented approach
Medical Engineering & Physics, 2013
This article describes a feasibility study of a novel trans-scleral tonometer based on the use of an instrumented form of digital palpation tonometry. Similar to manual digital palpation tonometery, trans-scleral tonometer utilizes two force probes offset by a fixed distance. Force indentation data from these probes have been shown to correlate with the intraocular pressure (IOP) of the eye. Enucleated porcine eyes were used to experimentally validate the approach. The observed hysteresis in the force data was analyzed using an analytical model that accounts for the outflow of the aqueous humor. The predictions of the model indicate that the primary reason behind the observed hysteresis is stress relaxation (accommodation) in the visco-elastic corneo-scleral shell. Experimental data from eye distention and indentation tests were then used to infer the conditions under which the novel tonometer would be expected to have an accuracy of ±1 mmHg. Analysis of the data shows that indentation rates should be kept below 0.5 mm/s for a pressure range of 10-35 mmHg. Two commonly used pressure control protocols were tested in an effort to ensure accurate IOP values during the palpation tests. Due to the large increase of IOP during digital palpation, the trans-scleral (intra-vitreous) pressurization was found to be inadequate, leading to clogging of the line by the displaced vitreous. No such problems were identified when the eye was pressurized through the cornea and into the anterior chamber. Force data from multiple palpation experiments are used to generate calibration curves for a two-probe conceptual tonometer. The calibration showed that a 10 mN of force variation corresponds to 1 mmHg of IOP change. A possible implementation using a contoured facial mask is also presented.
Validation of the Icare® TONOVET plus rebound tonometer in normal rabbit eyes
Experimental Eye Research, 2019
To determine the accuracy and precision of the Icare® TONOVET Plus rebound tonometer for measuring intraocular pressure (IOP) in normal rabbit eyes, as well as compare it to three other commercially available tonometers: the Icare® TONOVET (TV01), Tono-Pen Vet™, and Tono-Pen AVIA Vet™. The anterior chambers of both eyes of three New Zealand White rabbits were cannulated, post-mortem. IOP was measured using each of the above four tonometers at manometric pressures ranging between 5 mmHg and 70 mmHg. Data were analyzed by linear regression, ANOVA, and Bland-Altman plots. A p-value of ≤ 0.05 was considered significant for all statistical tests. IOP values obtained with the TONOVET Plus (in 'lapine' mode) were significantly closer to manometric IOP than those obtained with the other tonometers tested. The TV01 (in 'd' dog setting) and Tono-Pen AVIA Vet™ were significantly more accurate compared to the Tono-Pen Vet™. All tonometers had high levels of precision, though the TONOVET Plus and TV01 were significantly more precise compared to the Tono-Pen AVIA Vet™. All tonometers tended to underestimate IOP, particularly at high pressures, however the TONOVET Plus was highly correlated with manometric IOP in the clinically relevant range of 5-50 mmHg. The TONOVET Plus is an appropriate choice of instrument for measuring IOP in rabbit eyes in both research and clinical settings.
Comparison of intra-ocular pressure measurement with four different methods of tonometry
Indian Journal of Clinical and Experimental Ophthalmology, 2021
The aim of this study was to measure the intraocular pressure (IOP) by Perkins hand held tonometer, non contact tonometer(NCT) and rebound tonometer with the Gold standard GAT and to analyse their correlation with varied CCT. Cross-sectional, hospital- based study that included 200 patients from the glaucoma department. After complete eye evaluation, the IOP measurement was performed sequentially in the same order- NCT, RT, Perkin’s and GAT. CCT was then measured for all the patients. The intra-ocular pressure within the eyes was compared by paired “t” test and between the right and left eyes were compared by the independent “t” test. Mean age of the patients was 54.5±13.5 years. The mean IOP of Right and Left eyes measured with GAT were 15.9±6.2 and 16.3±7.0 mm/Hg, that with Perkins were 15.7±6.2 and 16.3±7.0 mm/Hg respectively. Both eyes’ mean IOP were 15.4±6.7 and 15.9±7.4 mm/Hg by Icare. The mean IOP measured by NCT were 16.4±6.7 and 16.9±8.0 mm/Hg. The mean CCT of right eye was...
Reliability of the non-contact tono-pachymeter Tonopachy NT-530P in healthy eyes
Clinical and Experimental Optometry, 2013
Background: Non-contact Tonopachy NT-530P (Nidek Co., LTD) provides intraocular pressure (IOP) and central corneal thickness (CCT) measurements. This study assesses the reliability and repeatability of its IOP measurements in young healthy adult subjects. Methods: IOP was determined in the right eye of 64 healthy patients using Tonopachy followed by the Canon TX-10 non-contact and Goldmann applanation (GAT) tonometers. Tonopachy IOP measurements were corrected (Tonopachy-C) or not (Tonopachy-NC) by the instrument for central corneal thickness. Central corneal thickness measurements provided by Tonopachy were also used to correlate (Pearson's coefficient) central corneal thickness with the GAT and Canon TX-10 IOPs. Repeatability of Tonopachy and GAT was assessed in the right eye of 31 subjects in two separate sessions one week apart. Differences between pairs of instruments and between sessions were determined using Bland-Altman plots. The coefficient of repeatability was calculated as the 95% limits of agreement (LoA) of differences between the two sessions.
Reproducibility and Clinical Evaluation of Rebound Tonometry
Investigative Opthalmology & Visual Science, 2005
How to Measure Intraocular Pressure: An Updated Review of Various Tonometers
This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Intraocular pressure and ocular pulse amplitude using dynamic contour tonometry and contact lens tonometry
BMC ophthalmology, 2004
The new Ocular Dynamic Contour Tonometer (DCT), investigational device supplied by SMT (Swiss Microtechnology AG, Switzerland) allows simultaneous recording of intraocular pressure (IOP) and ocular pulse amplitude (OPA). It was the aim of this study to compare the IOP results of this new device with Goldmann tonometry. Furthermore, IOP and OPA measured with the new slitlamp-mounted DCT were compared to the IOP and OPA measured with the hand-held SmartLens,a gonioscopic contact lens tonometer (ODC Ophthalmic Development Company AG, Switzerland). Nineteen healthy subjects were included in this study. IOP was determined by three consecutive measurements with each of the DCT, SmartLens, and Goldmann tonometer. Furthermore, OPA was measured three times consecutively by DCT and SmartLens. No difference (P = 0.09) was found between the IOP values by means of DCT (mean: 16.6 mm Hg, median: 15.33 mm Hg, SD: +/- 4.04 mm Hg) and Goldmann tonometry (mean: 16.17 mm Hg, median: 15.33 mm Hg, SD: +...
Related topics
Loading Preview
Sorry, preview is currently unavailable. You can download the paper by clicking the button above.