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Pinakin Gunvant Davey, John Maggiano, Laz C Peterson, Steve Maurath, Peter Joson; Intraocular pressure estimates measured using a novel hand held tonometer. Invest. Ophthalmol. Vis. Sci. 2019;60(9):3195.
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© ARVO (1962-2015); The Authors (2016-present)
LightTouch® tonometer (LT) is a novel prototype contact, hand held tonometer that estimates intraocular pressure (IOPe) in-vivo under topical anesthesia. Here we present the preliminary principles and calibration data of the LT and provide in-vivo IOP measurements obtained using the LT and Tonopen.
The principles of measuring IOPe using the LT device are based on simultaneous, objective, digital area and force measurements. Area measurement occurs via a decrease in total internal reflection within the device. This occurs when the device tip touches the corneal apex. Force is measured via a proprietary piezoelectric assembly. The distal end of the device contains an acrylic prism with a flat tip of 3.06 mm diameter. As the prism tip approaches the central cornea, the technician observes an aiming beam transiting the central cornea, and the patient assists in alignment by viewing the aiming beam target. After appropriate alignment the technician then briefly touches the corneal apex with a duration of 0.1 to 0.15 seconds, with a force of about 1 gram. During the touch duration the technician can see the measuring beam light (as it decouples from the device) illuminating the iris.Calibration experiments were performed utilizing a precise, programmable motorized sled with either 3.06 or 4.00 mm probe tip devices anchored to the sled. A rubber ball with duro and curvature similar to a human cornea was utilized. The calibration goal was to understand whether the probe construction yielded repeatable measurements at various force increments. The LT and Tonopen measurements were performed in two individuals.
Calibration experiments show highly repeatable measures performed by LT on a rubber ball (see figure 1a). The figures-1 B&C show the force and area measures of a single touch on a human cornea as a function of time with the LT device. In-vivo IOP was measured using the LT and Tonopen on investigator eyes, and shows 1mmHg measure of Tonopen corresponds to 3.5-4.5 LT force units.
The laboratory experiments indicate that the LT device measures are very repeatable at differing forces. The LT device can provide IOPe data that is very sensitive to various fluctuations. Further in-vivo data and comparison results to other tonometers will establish the validity of LT at all IOPe values.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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