Abstract: OBJECTIVE To study the in vitro release and corneal permeation of a thermoresponsive ophthalmic in situ gel containing bendazac lysine. METHODS The effect of the concentration of Poloxamer407 and 188 on the gelation temperature was evaluated, then the results were fitted with second-order quadratic models to optimize the formulation. Using aqueous solution or eye drops as control, the in vitro release of the formulation was evaluated by membrane-less method, dialysis bag method and dialysis membrane method. Then, the corneal permeation experiment of the optimum formulation was carried out with Franz diffusion cells. RESULTS The optimium formulation had low corneal irritation, gelling temperature of 31.5 ℃, pH of 6.95, and osmotic pressure of 397 mOsmol·kg^-1. Compared to the control group, the optimum formulation had significant sustained release effect without burst release. The result of the corneal permeation showed that the corneal permeation rate of the in situ gel was lower than the eye drops. CONCLUSION With significant sustained release effect, the thermoresponsive ophthalmic in situ gel will become a promising alternative formulation for bendazac lysine which was used for treating cataract.