Development of Inductive and Capacitive Type Intraocular Pressure (IOP) Sensor to Improve Sensitivity and Minimize Size

Abstract

We had presented an inductive type intraocular pressure sensor (L-sensor) in previous work. The distance between a micro coil and a ferrite on the membrane was modulated by pressure, and as a result the inductance and resonant frequency were changed. However, L-sensor has some problems to implant in eyes. First problem is low sensitivity. When L-sensor was implanted in rabbit's eyes, resonant frequency of L-sensor was very hard to detect. Second problem is biocompatibility. Size of L-sensor is 6×7×1.2 mm. When L-sensor was implanted in the eyes, it caused the inflammation. Therefore, this study suggests an inductive and capacitive type IOP sensor (LCsensor). The sensitivity of the LC-sensor 27.3 kHz/mmHg under 60 mmHg. It is much larger than 14 kHz/mmHg of the L-sensor. And the size of LC-sensor is 47% smaller than L-sensor. After 2 weeks from the implantation of LC-sensor into rabbit eyes, we measured the changes of resonant frequency of LC-sensor according to increased IOP by Balanced Salt Solution (BSS) injection. As a result, the sensitivity of LC-sensor in in vivo test is 25 kHz/mmHg. That is similar to the sensitivity of in vitro test. Received : Oct. 30, 2014, Revised : Nov. 28, 2014, Accepted : Nov. 28, 2014 This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License(http://creativecommons.org/ licenses/bync/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.