Dry eye is a multifactorial disease of the tears and ocular surface that results in symptoms of discomfort,visual disturbance,and tear film instability with potential damage to the ocular surface.Common subjective complaints included ocular dryness,redness,itching of eye,foreign body sensation,etc.In recent years,with increasing morbility of the dry eye,people has paid more and more attention to the dry eye.This article reviews diagnosis,categorization,etiology and epidemiology of the dry eye