Disclosed is novel use of 2-phenyl-1,2-benzisoselenazol-3(2H)-one or a salt thereof for medical purposes. 2-Phenyl-1,2-benzisoselenazol-3(2H)-one or a salt thereof exerts excellent prophylactic and ameliorating effects in a corneal disorder model, and is therefore useful as a prophylactic or therapeutic agent for corneal and conjunctival disorders such as dry eye, superficial punctate keratopathy, corneal epithelial loss, corneal erosion, corneal ulcer, conjunctival epithelial loss, keratoconjunctivitis sicca, superior limbic keratoconjunctivitis, filamentary keratoconjunctivitis, keratitis and conjunctivitis.
