Abstract
Tear fluid contains a diverse array of biomarkers reflective of both ocular and systemic health, making it a valuable medium for noninvasive diagnostics. Contact lens biosensors, integrated with optical sensing technologies, provide a promising platform for real-time, continuous monitoring of tear fluid composition. This review focuses on recent advances in the development of contact lens biosensors for optical detection of tear-based biomarkers. Key components include biocompatible lens materials, such as hydrogels and silicone hydrogels, that maintain oxygen permeability and optical clarity, along with fabrication methods such as inkjet printing, micropatterning, and three-dimensional (3D) microfabrication for precise sensor integration. Optical sensing mechanisms, including fluorescence, photonic crystal resonance, and surface plasmon resonance, have demonstrated high sensitivity in detecting glucose, lactate, electrolytes, cortisol, and inflammatory markers at clinically relevant concentrations. Such sensors have shown potential in diagnosing and monitoring diseases including diabetes, dry eye syndrome, stress-related disorders, and neurodegenerative conditions. Despite these advances, challenges remain in minimizing background interference, enabling long-term wear, and achieving multiplexed detection. Future research should prioritize robust biorecognition chemistries, wireless optical readouts, and scalable manufacturing strategies to support clinical translation. Contact lens biosensors are poised to become a key platform in next-generation, personalized healthcare through noninvasive tear fluid analysis.