Telemetric Monitoring of Intraocular Pressure Using the OccuTack Wireless Pressure Sensor

Abstract

 

Purpose:

 

Test a proprietary wireless pressure sensor’s ability to monitor intraocular pressure (IOP) in conscious, freely moving rabbits for one month.

 

Methods:

 

The OccuTack wireless pressure sensor was previously tested in vitro using a plastic water balloon. These studies established a linear correlation between the natural resonance frequency of the sensing system in relation to the pressure exerted on the sensor; serving as the proof of concept for OccuTack implantation ex vivo into cadaver eyes and in vivo into rabbit eyes. Four OccuTack sensors were implanted into rabbit eyes. The cannula was inserted into the vitreous space via a pars plana approach superotemporal (n=2) or superonasal (n=2) through a conjunctival fornix incision. IOP readings were recorded on post-operative day 1 and weeks 1, 2, and 4. Eyes were then explanted with the pressure sensor remaining intact. Each eye was artificially pressurized over a standard curve to ensure continued linearity of the sensor frequencies emitted after one month of continual implantation (see Fig. 1). A second set of Occutack sensors (n=4) were implanted into cadaver eyes, and full standard pressure curves were generated at 1, 2, 3, and 4 weeks post implantation to examine frequency drift.

 

Results:

 

Three of the four pressure sensors were successfully implanted, and two provided excellent signal for the entire month. Superonasal implantation is ideal in rabbits as the nictitating membrane provided additional protection of the implant. Histopathologic analysis of the eyes showed that the pressure sensor was fully encapsulated after one month with only mild inflammatory reaction. All sensors show a predictiable amount of drift over the study period.

 

Conclusions:

 

The prototype OccuTack wireless pressure sensor was successfully transitioned to in vivo experiments. The OccuTack sensor represents a pivotal step toward the development of a wireless pressure sensor for continuous telemetric IOP monitoring in humans.  

 

Keywords: intraocular pressure • circadian rhythms • anatomy