Objective To detect the difference of the light sensitivity in the central visual field between normal people and type Ⅱ diabetic patients without diabetic retinopathy, and evaluate the effect of perimetric examination in early diagnosis of diabetic retinopathy. Methods The light sensitivity at the 80 locations in the central field was measured by Dicon field analyzer (model TKS-4000) in 76 normal eyes of 44 normal volunteers aged from 45 to 72 years and 75 eyes of 40 type Ⅱ diabetic patients without retinopathy aged from 46 to 71 years. Results For the diabetic patients without diabetic retinopathy, the light sensitivity of locations decreased by 4-8 dB,and there were some decreased light sensitivity areas. The mean light sensitivity of three zones of the central field had significant reduction in the diabetic patients as compared with the control group(Plt;0.001). Conclusion The retinal neurosensory function of diabetic patients is damaged in some degrees before diabetic retinopathy occured, and no relationship is found between the decrease of retinal light sensitivity and localized blood-retinal barrier leakage. It is suggested that examination of central field with computerized perimetry has certain clinical significance in early diagnosis of diabetic retinopathy. (Chin J Ocul Fundus Dis, 2002, 18: 218-220)