| Background Diabetic autonomic neuropathy (DAN) is a recognized complication of type 2 diabetes mellitus, and may involve the pupil. One pupillary manifestation of DAN is small pupil size but the mechanism for this is unclear despite a number of studies that have assessed pupil function in diabetic patients using both static and kinetic methods. Diabetic neuropathy is generally classified into somatic and autonomic neuropathy. Although somatic neuropathy can be characterized by symptoms such as numbness, paresthesia, and abnormal sensation, the symptoms of autonomic neuropathy do not appear until the advanced stage. DAN causes functional disorders of many organs, such as cardiovascular, gastrointestinal, genitourinary, metabolic, and pupillary dysfunctions. Among these, cardiovascular autonomic neuropathy may increase the risk of sudden death and affects the mortality of diabetic patients. Heart Rate Variability (HRV) level is a reliabletool to assess DAN. DAN develops within a short duration of diabetes even when somatic neuropathy is not apparent. Furthermore, the abnormalities in pupillary functions can be detected earlier than those in cardiovascular autonomic functions and are considered the earliest signs of diabetic autonomic neuropathy. Therefore, the early diagnosis and treatment of DAN is important as it is often asymptomatic in its early stages but it is associated with a worse prognosis. And that whether the somatic and autonomic neuropathy is related is argumentative.Objective To investigate the early DAN through the analysis of the pupil diameter under mesopic, photopic and pharmacologically dilated conditions. Compared with the detection of the early DAN and with the results of HRV to determine whether there are systematic changes in pupil size and which index is more sensitive. At the same time, to analysis the relativity of DAN with the somatic neuropathy.Methods Type 2 diabetic patients were selected at random from the Diabetic Department of the Second Hospital affiliated to Zhejiang University, and the Group of the controls were selected from the outpatients of the Eye center of the same Hospital from March 1 2003 to March 6 2004. Cases were sorted to three groups: the controls, the subclinic ones and the nonproliferative diabetic retinopathy (NPDR) according to fundus fluorescein angiography. High resolution images of the pupil of the eyes of 60 subjects were taken using IR sensitive camera Sony F717. Images were obtained under mesopic (Dl), photopic (D2), and pharmacologically dilated conditions (D3) (1% Tropicamide, four times, two drops every time, five minutes interval). From the images, the pupil diameters were computed and calculated using Photoshop, Acdsee, and Imagetools software. In addition, Dilation Ratio [DR=(D3-D1)/D1 ] and Constriction Ratio [DR=(D1-D2)/D1 ] were accounted. Both the pupil size and the DR and ER were used to analyze the DAN, compared with the results of HRV (detected by the DMS7.0 Holter) to determine which were more sensitive. At the same time, relation analyzing with the somatic neuropathy was made, which was detected by electromyography (Key point 4).Results1. There was no significant difference among groups with age. under mesopic conditions, the pupil diameters of the subclinic group, the NPDR and the controls were 5.87 0.99mm , 4.95 1.12mm, 6.02 0.48mm respectively. The differences of the measured data in these three methods were statistically significant (ANOVA, p=0.002). After dilated with 1% Tropicamide Eye Drops, the pupil diameters of the three groups also showed significant difference (ANOVA, p=0.0000) with the results measured were 3.45 0.50mm, 2.83 0.61mm, 3.64 0.42mm separately. And it should be noted that there was significant difference among groups with the dilation ratio which were 0.19 0.03, 0.15 0.08, 0.22 0.10 (ANOVA, p=0.001). But, there was no significant difference among the three groups with pupil diameters under photopic conditions which were 3.37 0.3mm, 3.25 0.47mm, 3.40 0.33mm. And also the CR among groups showed no sign...
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