The present invention relates to a sterile aqueous ophthalmic solution comprising N-(N-acetylcysteinyl-)chitosan or a pharmaceutically acceptable salt thereof in a carrier solution, wherein the N-(N-acetylcysteinyl-)chitosan has a content of free thiol groups in an amount of from 80 µmol/g polymer to 280 µmol/g polymer, for use in the treatment of corneal wounds.