Engineering Vision: The Comparative Role of 3D Printing and 3D Bioprinting in Corneal Regeneration

Corneal blindness remains a major global cause of vision loss, and the limited availability of donor tissue has intensified efforts to engineer functional corneal substitutes with appropriate optical, mechanical, and biological performance. Advances in additive manufacturing have positioned 3D printing and 3D bioprinting as promising platforms for fabricating anatomically informed constructs that may recapitulate key aspects of the cornea's hierarchical architecture. This review provides a mechanistic comparison of these technologies with respect to material systems and (bio)ink formulation, processing strategies, scaffold architecture, cell incorporation, and biological integration. Particular emphasis is placed on the trade-off between high-fidelity 3D-printed scaffolds that can be seeded after fabrication and cell-laden bioprinted constructs that better capture early cell-matrix interactions but remain constrained by bioink rheology, resolution, mechanical integrity, and shape retention.The review further examines emerging strategies, including decellularized extracellular matrix bioinks, functionally graded hydrogels, and hybrid electrospun-printed constructs, for improving bioactivity, structural mimicry, collagen alignment, optical transmittance, and stromal-like extracellular matrix deposition. Persistent challenges include nanoscale and membrane-like architectural replication, longterm phenotype stability, reproducible manufacturing, surgical handling, storage, and regulatory classification of combination products. By integrating material science, fabrication physics, cellular responses, and translational considerations, this review delineates the complementary roles of 3D printing and 3D bioprinting and identifies the key design criteria required to advance printed corneal constructs toward clinically translatable regeneration.