·AIM:To observe the effects of extended soft contact lens(SCL)wear on the ocular superficial epithelial and analyze the possible mechanism.·METHODS:The subjects were divided into three groups according to the wearing hours of SCL.Fluorescein vital staining(FLS),conjunctival impression cytology(CIC)were used in normal control group(35 cases 70 eyes)and experiment group(99 cases 198 eyes).The differences of FLS,goblet cell density(GCD)and grade of squamous metaplasia were analyzed.·RESULTS:There were statistical differences in FLS,GCD and grade of squamous metaplasia between the group wearing SCL for less than 12 hours,12 to 24 hours or more than 24 hours(P<0.05).However,there were no statistical differences in FLS,GCD and grade of squamous metaplasia between the group wearing SCL for 12 to 24 hours and more than 24 hours.·CONCLUSION:Extended SCL wear can cause the ocular surface injury,decrease conjunctival goblet cells and conjunctival epithelium keratinized,and the longer the wear,the obvious the change.·