Objective To evaluate autonomic nervous function lesions in eyes with type 2 diabetes mellitus by investigating pupil diameters under the natural state and drug-induced dilated conditions and maximum binocular amplitude adjustment. Methods In this prospective cohert study, 80 type 2 diabetic patients from Peking University Shenzhen Hospital were divided into two groups based on the results of fundus fluorescene angiography (FFA), a preclinical group and a non-proliferative group with 40 patients in each group. Thirty age-matched healthy people were selected as controls. Maximum binocular amplitude adjustment was tested with a comprehensive refractometer, pupil diameters under the natural state and drug-induced dilated conditions were measured with corneal topography. A one-way ANOVA was used for data analysis. Results The mean pupil diameters of the two eyes under the natural state in the control group, preclinical group and non-proliferative group were the same, 2.92±0.47 mm, 3.14±0.65 mm, and 3.24±0.58 mm, respectively. The differences between the groups were not statistically significant (F=2.637, P>0.05). For the right eyes, the mean pupil diameters under the drug-induced dilated conditions were 7.28±0.64 mm, 6.66±0.95 mm, and 6.42±1.32 mm, respectively. The differences between the groups were not statistically significant (F=6.008, P<0.05). The mean diameters for the left eyes were 7.37±0.63 mm, 6.50±1.21 mm, and 6.51±1.04 mm, respectively. The differences between the groups were statistically significant (F=7.737, P<0.05). For the right eyes, the mean dilation ratios were 1.56%±0.47%, 1.16%±0.32%, and 0.98%±0.32%, respectively. The differences between the groups were statistically significant (F=21.620, P<0.05). The ratios for the left eyes were 1.59%±0.47%, 1.11%±0.36%, and 1.04%±0.32%, respectively. The differences between the groups were significant (F=20.289, P<0.05). The mean maximum binocular amplitude adjustments were +4.87±2.53 D, +3.01±1.66 D, and +2.38±1.53 D, respectively. The differences between the groups were significant (F=15.478, P<0.05). Further comparison showed that the drug-induced pupil diameter, dilation ratio and maximum binocular amplitude adjustment in the control group were higher than in the preclinical and non-proliferative groups (P<0.05). Conclusion eye sympathetic nerve lesions and eyes symmetry parasympathetic nerve functional lesion occurs early in type 2 diabetes.