This Book Contain a reveiw and research details on Stimuli sensitive hydrogels. These hydrogels are based on a concept of phase transformation of solution into viscous gel due to presence of stimuli i.e. pH, Temperature, Ionic concentration etc. Here, we are studying about Ophthalmic Hydrogels which are initially liquid in container but transforms into viscous gel when instilled into eye cavity due to the stimuli i.e.change in pH. Basic composition of hydrogels are API, poly acrylic acid polymer, viscolizers, chealating agents, isotonic agents etc.