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Abstract #3459 Published in IGR 4-2
Clinical evaluation of the dynamic observing tonometer
Morgan AJ; Hosking SL; Salmon JFJournal of Glaucoma 2002; 11: 334-339
PURPOSE: The Dynamic Observing Tonometer (SmartLens, Ophthalmic Development Company AG, Zürich, Switzerland) is a diagnostic contact lens that allows continuous measurement of intraocular pressure (IOP), in addition to providing the investigator with a view of the posterior pole and anterior chamber angle. The purpose of this study was to determine the accuracy of this tonometer and the repeatability of the IOP measurements. PATIENTS AND METHODS: The IOP was measured by Goldmann applanation tonometry in one randomly chosen eye of 40 subjects (median age, 66 years; range, 21-77 years). The IOP pulse amplitude and ten-second continuous tonometric recordings were then taken using the Dynamic Observing Tonometer and a pneumatonometer. Accuracy was determined by calculating the mean bias and 95% limits of agreement of measurements made with the Dynamic Observing Tonometer against measurements made with the Goldmann and pneumatonometer. Repeatability was evaluated by calculating the differences between pairs of repeated measurements against the mean value and by calculating reliability coefficients. RESULTS: IOP measurements made with the Dynamic Observing Tonometer had a mean bias of +2.1 mmHg (95% limits of agreement: -4.0 to +8.2 mmHg) compared with Goldmann tonometry. There was a reasonable correlation between Goldmann and Dynamic Observing Tonometer IOP readings (r = 0.78, p < 0.01). In measuring pulse amplitude, the Dynamic Observing Tonometer was found to have a mean bias of +0.4 mmHg (95% limits of agreement: -1.6 to +2.3 mmHg) compared with the pneumatonometer (r = 0.78, p < 0.01). In assessing the repeatability of IOP measurements, the first Dynamic Observing Tonometer reading was on average 0.4 mmHg higher than the second (95% limits of agreement: -3.8 to +4.6 mmHg) with a coefficient of reliability of 0.91. For pulse amplitude readings, the first reading was on average 0.1 mmHg lower than the second (95% limits of agreement: -1.4 to +1.2 mmHg) with a coefficient of reliability of 0.90. CONCLUSIONS: IOP measurements taken with the Dynamic Observing Tonometer had a small positive bias compared with Goldmann tonometry. The pulse amplitude values correlated well with those obtained with a pneumatonometer and the repeatability of IOP measurements was similar to that found in other commercially available tonometers.
Dr. S.L. Hosking, Neurosciences Research Institute, School of Life and Health Sciences, Aston University, Aston Triangle, Birmingham, B4 7ET, UK. s.l.hosking@aston.ac.uk
Classification:
6.1 Intraocular pressure measurement; factors affecting IOP (Part of: 6 Clinical examination methods)
