A minimally invasive implantable wireless pressure sensor for continuous IOP monitoring.
This paper presents a minimally invasive implantable pressure sensing transponder for continuous wireless monitoring of intraocular pressure (IOP). The transponder is designed to make the implantation surgery simple while still measuring the true IOP through direct hydraulic contact with the intraocular space. Furthermore, when IOP monitoring is complete, the design allows physicians to easily retrieve the transponder. The device consists of three main components: 1) a hypodermic needle (30 gauge) that penetrates the sclera through pars plana and establishes direct access to the vitreous space of the eye; 2) a micromachined capacitive pressure sensor connected to the needle back-end; and 3) a flexible polyimide coil connected to the capacitor forming a parallel LC circuit whose resonant frequency is a function of IOP. Most parts of the sensor sit externally on the sclera and only the needle penetrates inside the vitreous space. In vitro tests show a sensitivity of 15 kHz/mmHg with approximately 1-mmHg resolution. One month in vivo implants in rabbits confirm biocompatibility and functionality of the device.
School of Mechanical Engineering, Purdue University, West Lafayette, IN 47907, USA. gchitnis@purdue.edu
Girish
G
Chitnis
Teimour
T
Maleki
Brian
B
Samuels
Louis B
LB
Cantor
Babak
B
Ziaie
D000818:Animals; D006651:Histocytochemistry; D007429:Intraocular Pressure / Q000502:physiology*; D055616:Microtechnology / Q000295:instrumentation; D019060:Minimally Invasive Surgical Procedures; D019736:Prostheses and Implants; D011474:Prosthesis Design; D011817:Rabbits; D012590:Sclera / Q000601:surgery; D014065:Tonometry, Ocular / Q000295:instrumentation* / Q000379:methods; D059015:Wireless Technology / Q000295:instrumentation*