A contact lens sensor system with a micro-capacitor for wireless intraocular pressure monitoring

This paper proposes a novel micro-capacitor sensor for intraocular pressure (IOP) measurement on soft contact lens. The sensor was designed and fabricated by using MEMS fabrication technologies. The contact lens is for wearing on a cornea such that a curvature of the contact lens corresponds substantially to that of the cornea, and is preferably made of Hydroxyethylmethacrylate (HEMA) by cast-molding method of soft contact lens for high oxygen permeability and comfortable long-duration wearing. The prototype without wireless antenna has been implemented with a sensitivity of 0.43 pF/mmHg in measurement of human eye like balloon pressure test between 100 mmHg and 180 mmHg. The results show its high stability and reproducibility in a series of repeatable pressure variation. In future work the micro-capacitor will be tested on enucleated porcine eyes with better and integrated with a radio frequency integrated circuit and antenna on soft contact lens so that IOP value could be transferred to voltage value via capacitor to voltage converter and transmits IOP sensing signal by wireless telemetry system.