Hydrogels as Promising Carriers for Ophthalmic Disease Treatment: A Comprehensive Review.

Ocular disorders such as keratitis, glaucoma, age-related macular degeneration (AMD), diabetic retinopathy (DR), and dry eye disease (DED) are highly prevalent worldwide and remain major causes of visual impairment and blindness. Conventional therapeutic approaches for ocular diseases, such as eye drops, surgery, and laser therapy, are frequently hampered by limited drug bioavailability, rapid clearance, and treatment-related complications, primarily due to the eye's unique anatomical and physiological barriers. Hydrogels, characterized by their three-dimensional network structure, high water content, excellent biocompatibility, and tunable physicochemical properties, have emerged as promising platforms for ophthalmic drug delivery. This review summarizes the classification, fabrication strategies, and essential properties of hydrogels, and highlights recent advances in their application to ocular diseases, including keratitis management, corneal wound repair, intraocular pressure regulation and neuroprotection in glaucoma, sustained drug delivery for AMD and DR, vitreous substitutes for retinal detachment, and therapies for DED. In particular, we highlight recent advances in stimuli-responsive hydrogels that enable spatiotemporally controlled drug release in response to ocular cues such as temperature, pH, redox state, and enzyme activity, thereby enhancing therapeutic precision and efficacy. Furthermore, this review critically evaluates translational aspects, including long-term ocular safety, clinical feasibility, manufacturing scalability, and regulatory challenges, which are often underrepresented in existing reviews. By integrating material science, ocular pathology, and translational considerations, this review aims to provide a comprehensive framework for the rational design of next-generation hydrogel systems and to facilitate their clinical translation in ophthalmic therapy.