Functional Polymer-Based Biomaterials for Corneal Tissue Engineering: An Indication-Guided Review of Design Trade-Offs.

Corneal disease is a cause of vision loss worldwide, while conventional keratoplasty is constrained by limited donor tissue and immune rejection. This indication-guided review examines functional polymer platforms for corneal tissue engineering, including natural polymers, synthetic polymer networks and scaffolds, and hybrid polymer composites. It examines how molecular composition, crosslinking, architecture, surface functionalization, and fabrication influence hydrogels, films, fibrous scaffolds, injectable matrices, delivery systems, and polymeric keratoprosthetic components for epithelial, stromal, and endothelial contexts. Using an indication-guided design trade-off framework, the review compares these systems across optical performance, mechanical performance and surgical handling, mass transport and degradation behavior, biological function and tissue integration, host response, and manufacturability. Natural polymers can provide biological cues that support cell interactions, with limitations in mechanical robustness and compositional consistency. Synthetic polymers offer greater control of network properties and processing but often require biofunctionalization to support tissue integration. Hybrid constructs can distribute optical, structural, and therapeutic functions across components or regions, with added fabrication complexity. No material class is universally optimal, and polymer selection should be guided by the target corneal layer and clinical indication. Standardized evaluation, reproducible reporting of polymer composition and fabrication conditions, scalable manufacturing, and transparent reporting of evidence maturity are priorities for clinical translation.