Development of An Inductive Sensing Contact Lens Sensor with Environmental Reference for Continuous Intraocular Pressure Monitoring

Speaker :
Mr Ching Hymn Christopher LEE
Department of Mechanical and Aerospace Engineering, HKUST
Date : 15 Jan 2019 (Tue)
Time : 10:00 am
Venue : Room 2550, HKUST (2/F., Lift #27/28)


Intraocular pressure (IOP) is a dynamic parameter with variations over 24-hours in the eye. For the diagnosis and treatment of IOP-related diseases such as glaucoma, clinically established spot IOP measurements cannot capture the full circadian rhythm of IOP in patients. As a result, a 24-hour IOP profile would be immensely beneficial and clinically relevant for the treatment of IOP related diseases. Continuous and non-invasive IOP measurements have been made possible with the introduction of contact lens sensors (CLS). Upon corneal changes due to IOP variations, deformation from the cornea is directly transferred to the contact lens by surface tension forces. An electrical circuit embedded into the lens tracks the resulting deformation of the CLS and a wireless system delivers the signal to an external reader. However, despite the thin build of the inductive sensing CLS, the passive nature of the circuit is not selectively sensitive to IOP when worn on the human eye. Environmental changes near the CLS invalidates the previously established linear resonant frequency to IOP relationship.

In this thesis, the environmental influences from the human eye were shown on a silicone model eye, and a new inductive sensing CLS was designed and fabricated to remove the environmental influences. The rigid-flex CLS includes a rigid passive inductor-capacitor (LC) resonator placed beside another a separate LC resonator with higher flexibility. The flexible LC resonator is sensitive to intraocular pressure change as well as environmental influences; while the rigid coil only senses the environmental conditions. Results show the feasibility of removing the environmental influence from IOP measurements with the rigid flex contact lens sensor.

(Supervisor: Prof. David Chuen-Chun Lam)