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Milko Iliev, John Thygesen, Evelien Vandewalle, Julian Garcia-Feijoo, Salvador Garcia-Delpech, European Triggerfish Study Group; Randomized Clinical Investigation to Assess the Efficacy of SENSIMED Triggerfish® Continuous IOP Monitoring. Invest. Ophthalmol. Vis. Sci. 2013;54(15):5627.
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The need of a reliable intraocular pressure(IOP) monitoring in glaucoma patients is widely recognized. The new contact lens based sensor Triggerfish® (TF) uses an embedded strain gauge to detect circumferential changes in corneal periphery as a result of IOP change, and records fluctuations from baseline in Millivolts. The purpose of this study was to assess the correlation of TF readings with the IOP values of two clinically established tonometers, the Goldmann applanation (GAT) and the ICare PRO rebound tonometer
This was a multi-center, randomized, clinical trial. Patients with primary open-angle glaucoma were randomized into eight device groups and a control group. For the device groups, the randomly selected eye was assessed by continuous TF monitoring (Sensimed AG, Lausanne, Switzerland) for 3, 6, 9, 12, 15, 18, 21 or 24 hours and by tonometry before and after TF installation and every 3 h after TF removal until the end of 24-h period. The fellow eyes -as well as both eyes of patients in the control group- were assessed by ICare PRO and GAT at 3-h intervals over 24 hours. Paired comparisons were done between TF and tonometry measurements on fellow eyes in parallel and on the same eye at different time points during a 24-h period
Fifty-nine eligible patients were enrolled in five centers, 11 in the control and 48 in the eight device groups. Mean age was 64.8±10.8 y and 42.4% of patients were female. The regression modeling demonstrated that change in TF readings did not correlate and was not a predictor of change in IOP as measured by either GAT or ICare PRO tonometers. Within subject mean correlations (Pearson) between TF and tonometers in the fellow eye were low (r=0.22 for GAT, and r=0.06 for ICare PRO), and between the two tonometers were moderate (r=0.47 in the study, and r=0.51 in the fellow eye). Correlations were strong between study/fellow eye for the same tonometer (GAT, r=0.69; ICare PRO, r=0.60). Inclusion of blood pressure, refraction, axial length, corneal thickness, topography, and hysteresis did not change the above results
Changes in Triggerfish® signal cannot be related to changes in IOP as measured by clinical tonometry. This may be due to the difference in methodology, detection via central versus peripheral cornea, or other reasons. It is still poorly understood how to integrate the TF readings in our clinical practice.
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