Measuring intraocular pressure using solitary waves

Frequent measurements of intraocular pressure (IOP) are key to managing glaucoma, a chronic disease that leads to blindness. To date, the most common way to measure IOP is by applanation, a method that exploits the relationship between the IOP and the force necessary to deform the cornea by a certain amount. In this paper, the engineering principles behind a new device to measure eye pressure are investigated with the long-term objective of creating a personalized and portable biomedical device that anyone can self-proctor anytime anywhere. The device utilizes the propagation and detection of highly nonlinear solitary waves (HNSWs) within a chain of particles, the last of which is in contact with the eye to be assessed. The effect of IOP and central corneal thickness (CCT) on the characteristics of the HNSWs is investigated by testing five artificial corneas, made from polydimethylsiloxane, and two ex-vivo lamb corneas, subjected to pressure between 12 and 26 mmHg. The waveforms recorded during the experiment were then post-processed to extract the time of flight of the waves reflected from the chain specimen interface, which were found to be monotonically dependent on both the IOP and the CCT. The results of the study pave the way towards a new portable tonometer that patients can self-administer. • Glaucoma patients need frequent intraocular pressure checks to prevent blindness. • The thickness of a cornea impacts intraocular pressure predictions in typical tonometers. • Artificial corneas made of PDMS provide excellent corneal proxies with similar properties to biological corneas. • The proposed tonometer produces waveforms unique to BOTH pressure and corneal thickness. • PDMS and lamb corneas with similar thicknesses produce similar trends in the produced wave.