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I. Nwosuh, T. Alvarez, A.S. Khouri, R.D. Fechtner, G.A. Thomas; Testing of a Personal Tonometer Prototype for Measuring IOP . Invest. Ophthalmol. Vis. Sci. 2006;47(13):4434.
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© ARVO (1962-2015); The Authors (2016-present)
A personal tonometer for intra–ocular pressure (IOP) (analogous to a personal glucometer) is believed to be a useful tool that would aid in the diagnosis and monitoring of glaucoma. We have constructed a tonometer designed for trans–palpebral use and tested it on an artificial eye with variable pressure.
Electronic signals from the tonometer’s force and position sensors were passed through a Kiethley amplifier to a National Instruments Analog to Digital converter, then to a portable computer for analysis. The measurement curves were made three times for each pressure in the artificial eye, and the pressure was read with a water manometer. In the tests with the artificial eye, the range of forces from 0 to 3 grams was explored with an application area produced by a 3mm diameter cylinder. The displacement distances for the artificial cornea were 0 to 1mm.
The force curves as a function of displacement all showed curvature for displacements in the range of 0 to 0.2mm, with linear behavior at higher displacement with correlations of 0.98. The slopes were reproducible using the artificial eye with a mean difference of 0.01 to 0.03 within any given set of 3 measurements for 30 sets of measurements. The slopes scale with the manometer pressure according to a linear relationship with a correlation factor of 0.97 and p=0.0065.
The tonometer output shows a satisfactory correlation with pressure in lab trials, and indicates that measurements on human subjects are appropriate and may provide a practical approach for personal tonometry.
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