Lab on the Eye: A Review of Tear-based Wearable Devices for Medical Use and Health Management

Wearable sensors have garnered considerable interest because of their great promise in terms of personalized health and disease management. Tears are a superior target for wireless, non-invasive wearable devices, and tear-based platforms have developed rapidly over the past decade. Although an increasing number of tear analytes have been found to be associated with multiple diseases, glucose still serves as a main target for tear-based wearable devices. There has been much investment and efforts to develop tear-based wearable biosensors, with contact lens-based and spring-like sensors flourishing commercially. Current efforts have moved past ocular and systematic disease markers to nutrients and chemicals. Moreover, tear-based wearable devices also have the potential to treat some ocular diseases. This review discusses aspects of tear-based wearable devices and it emphasizes that strict clinical validation is needed before such platforms enter the market. Multifunctional and theranostic strategies would further broaden their clinical use in the future.