Hypromellose is a part of methyl and part of polyhydroxypropyl ether of cellulose. It can be dissolved in cold water to form a solution with a certain viscosity, and its properties are close to the viscoelastic substances (mainly mucin) in tears. Therefore, it can be used as artificial tears. Its mechanism of action is as follows: it attaches to the surface of the eyeball through the adsorption of the polymer, and simulates the action of conjunctival mucin, thereby improving the state of reduced mucin in the eye and increasing the retention time of the eyeball in the state of reduced tear. This adsorption is independent of the viscosity of the solution, thus enabling a persistent wetting effect for lower viscosity solutions. In addition, corneal wetting is increased by lowering the contact angle of the clean corneal surface.