title: A technique to measure eyelid pressure using piezoresistive sensors.
abstract: In this paper, novel procedures were developed using a thin (0.17 mm) tactile piezoresistive pressure sensor mounted on a rigid contact lens to measure upper eyelid pressure. A hydrostatic calibration system was constructed, and the influence of conditioning (prestressing), drift (continued increasing response with a static load), and temperature variations on the response of the sensor were examined. To optimally position the sensor-contact lens combination under the upper eyelid margin, an in vivo measurement apparatus was constructed. Calibration gave a linear relationship between raw sensor output and actual pressure units for loads between 1 and 10 mmHg ( R(2) = 0.96 ). Conditioning the sensor prior to use regulated the measurement response, and sensor output stabilized about 10 s after loading. While sensor output drifts slightly over several hours, it was not significant beyond the measurement time of 1 min used for eyelid pressure. The error associated with calibrating at room temperature but measuring at ocular surface temperature led to a very small overestimation of pressure. Eyelid pressure readings were observed when the upper eyelid was placed on the sensor, and removed during a recording. When the eyelid pressure was increased by pulling the lids tighter against the eye, the readings from the sensor significantly increased.
authors.affiliation: Contact Lens and Visual Optics Laboratory, School of Optometry, Queensland University of Technology (QUT), Brisbane, Qld. 4001, Australia. aj.shaw@qut.edu.au
authors.forename: Alyra J
authors.initials: AJ
authors.lastname: Shaw
authors.forename: Brett A
authors.initials: BA
authors.lastname: Davis
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Collins
authors.forename: Leo G
authors.initials: LG
authors.lastname: Carney
mesh_terms: D002138:Calibration; D003261:Contact Lenses; D005143:Eyelids / Q000502:physiology*; D006801:Humans; D016014:Linear Models; D008991:Monitoring, Physiologic / Q000295:instrumentation / Q000379:methods*; D011312:Pressure; D012815:Signal Processing, Computer-Assisted; D013696:Temperature