Optical point-of-care (POC) devices can be designed to be equipment-free, cost-effective, smartphone-integrated, and user-friendly. The chapter begins by examining the fundamentals of common optical materials relevant to POC applications, including chromogenic and fluorescent molecules, quantum dots, plasmonic materials, photonic crystals, and metasurfaces. Then, diverse optical transduction strategies are analyzed, including colorimetric, fluorescent, chemiluminescent, and surface-enhanced Raman scattering (SERS), and refractometric methods. The performance of diagnostic devices employing these transduction strategies is evaluated based on critical attributes for POC applications, such as ease of sample collection, deliverability, sensitivity, user-friendliness, and affordability. Throughout the discussion, representative references to specific diagnostic applications such as infectious disease detection, cancer screening, and continuous disease monitoring are provided.