Capacitive contact lens sensor for continuous non-invasive intraocular pressure monitoring

Intraocular pressure (IOP) is a primary indicative factor in the diagnosis and treatment monitoring of glaucoma. Measurement of IOP during conventional single office consultation is insufficient for determination of the pressure peak, and IOP profile is needed for peak determination. A capacitive wearable contact lens sensor for monitoring of the IOP is developed in this study. A curvature-sensitive inductor-capacitor sensor is fabricated and embedded inside a silicone rubber contact lens, such that the curvature of the lens is correlated with the resonance frequency of the sensor. The curvature of the lens is mechanically related to the IOP in the underlying eye such that the IOP can be determined from the resonance frequency of the sensor. To fit human eyes, the sensor was designed to have an outer diameter of 14 mm, radius of curvature of 8.5 mm, and operates in human IOP range between 5 and 40 mm Hg. The frequency responses and the ability of the sensor to track IOP cycles were tested. Tests on model silicone eyes and enucleated porcine eyes showed that the sensors have a linearity R>0.997 and a sensitivity >200 ppm/mmHg for IOP monitoring. Together with wireless reading circuitry taped around the eye socket, the new contact lens sensor can be used for continuous IOP monitoring in clinics and at home for determination of the peak IOP for use in glaucoma diagnosis and monitoring. (C) 2013 Elsevier B.V. All rights reserved.