Herpes simplex keratitis(HSK)is one of the most common ocular diseases, which is caused by Herpes simplex virus. More than 90% individuals have been infected with herpes simplex virus(HSV)in his lifetime. HSV establishes both neuronal latency and corneal latency. Stressful stimuli such as UV radiation, fever, stress, hypothermia, hyperthermia and surgical manipulation of the trigeminal ganglia can cause reactivation. The corneal lesions after HSV infection is mainly the result of the immunoreaction in which CD4⁺ cells appeared to be mediating the pathology, with CD8⁺ cells seemingly playing a protective role.