A Piezoresistive-Based Contact Lens for Non-invasive Intraocular Pressure Measurement

The second most common cause of blindness in the world is glaucoma. A key glaucoma indicator that can be monitored to treat the condition is intraocular pressure (IOP). A contact lens with a piezoresistive sensor to detect IOP continuously and non-invasively is proposed in this work. Two different contact lenses were fabricated, one with a sensing material made of carbon conductive paste and the other with graphene conductive paste. A screen-printing technique, which is a simple and inexpensive thin film-based technology was used for the fabrication of contact lenses. The fabricated contact lenses were tested for their transparency, waterproofing, ohmic contact, and sensitivity toward temperature. Results indicated that carbon conductive contact lens exhibited a sensitivity of 62.575 Ω/mmHg with a linear correlation coefficient of r² = 0.948. Conversely, the graphene conductive contact lens demonstrated a sensitivity of 44.43 Ω/mmHg with a linear correlation coefficient of r² = 0.974. The fabricated contact lenses complied with the fundamental requirements for contact lenses by being flexible, thin, and wrapped in a biocompatible material with high transparency.