Hydrogels are aqueous gels composed of cross-linked networks of hydrophilic polymers.
Stimuli-responsive based hydrogels have gained focus over the past 20 years for treating ophthalmic
diseases. Different stimuli-responsive mechanisms are involved in forming polymer hydrogel networks,
including change in temperature, pH, ions, and others including light, thrombin, pressure, antigen, and
glucose-responsive. Incorporation of nanocarriers with these smart stimuli-responsive drug delivery
systems that can extend the duration of action by increasing ocular bioavailability and reducing the dosing
frequency. This review will focus on the hydrogel drug delivery systems highlighting the gelling
mechanisms and emerging stimuli-responsive hydrogels from preformed gels, nanogels, and the role of
advanced 3D printed hydrogels in vision-threatening diseases like age-related macular degeneration and
retinitis pigmentosa. It also provides insight into the limitations of hydrogels along with the safety and
biocompatibility of the hydrogel drug delivery systems.