Hydroxypropylmethylcellulose is part of the methyl and part of the hydroxypropyl ether of cellulose. It can be dissolved in cold water to form a solution with a certain viscosity. Its properties are similar to the viscoelastic substances (mainly mucin) in tears. Therefore, it can be used as artificial tears. Its mechanism of action is that it attaches to the surface of the eye through the adsorption of polymer, and simulates the function of conjunctival mucin, thus improving the state of ocular mucin reduction and increasing the retention time of the eye in the state of tear reduction. This adsorption does not depend on the viscosity of the solution, so the solution with lower viscosity can also have a lasting wetting effect. In addition, the wetting effect of the cornea is increased by reducing the contact angle of the clean corneal surface.
