Advanced Corneal Hydrogels: From Passive Replacement to Active Regeneration and Intelligent Interaction.

Hydrogels represent a transformative solution for corneal pathologies, offering the advantages of transparency, biocompatibility, and structural tunability to address the global donor tissue shortage. This review establishes a comprehensive framework for material design by delineating critical requirements, including optical clarity, mechanical anisotropy, and stable wet adhesion within dynamic ocular environments. The performances of natural, synthetic, and decellularized-matrix hydrogels are systematically compared to elucidate the structure-property relationships essential for recapitulating native corneal physiology. Beyond passive substitution, the transition toward bioactive regeneration is examined through analyses of scarless wound healing, sustained drug delivery, and stimuli-responsive implants. Furthermore, the integration of advanced technologies is evaluated with a focus on three-/four-dimensional bioprinting for hierarchical architectural reconstruction and hydrogel-based wearable bioelectronics for real-time sensing. Finally, pivotal clinical translation bottlenecks, ranging from sterilization to long-term immunocompatibility, are identified to guide the development of next-generation personalized and intelligent corneal devices.