The present invention relates to a method of treating or preventing the visual function loss in optic nerve in a subject after crush injury by using 4-(Phenylsulfanyl)butane-2-one (4-PSB-2). The present invention has the ability of enhancing the protection effect of RGCs, preserving the visual function in optic nerve after crush injury, recovering the visual function loss, attenuating apoptosis in optic nerve after injury, and inhibiting the inflammatory responses in optic nerves after ON injury.