AIM:To investigate the variance of the irregular index of diabetics under ordinary circumstances and after sustained eye opening. ·METHODS:In 13 consecutive diabetics and 13 cases of non-diabetic controls (age and sex matched),we performed the Schirmer Ⅰ test (SⅠt),tear break-up time (BUT),fluorescein staining (FL) and symptom of dry eye questionnaires. Irregular index of corneal topography was also measured under routine circumstances and after sustained eye opening for 10 seconds,as a simulation of daily acts of gazing,which is defined as looking at an object with involuntary blink suppression. ·RESULTS:More diabetics (9/13 vs the control group 6/13) complained the presence of one or more symptoms of dry eye once a weak. When compared with the control group diabetics showed significantly decreased SⅠt (11.4±2.5 vs 14.9±3.3mm/5min,P<0.01 ) and BUT (10.9±4.7 vs 13.6±3.4s,P=0.02).None of values differed between FL of two groups (0.59±0.65 vs 0.29±0.54,P=0.06). The ordinary irregular index was higher in diabetics although the differences were not significant (1.36±0.46,1.11±0.45,P=0.06). However,after 10 seconds of sustained eye opening,the irregular index increased significantly to 4.23±1.32 in the diabetic group,whereas it remained at 2.08±0.60 in controls (P<0.01). ·CONCLUSION:In diabetics,reflex tearing and the tear film stability are demonstrated to be decreased. The SRI of diabetics increases when the eyes are kept open.