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Recently, Cahill et at1 published a paper on pupillary autonomic denervation in diabetic patients. In our own recent study we can confirm the presence of a small dark adapted pupil size (DAP) before cardiovascular autonomic dysfunction is detected in patients with type 1 diabetes mellitus.2 We believe that this is an important observation, since autonomic alterations may cause an increase in mortality as repeatedly evidenced for cardiac autonomic neuropathy (CAN).3
In particular, we found a significantly reduced DAP in patients with normal ranges in high frequency waves of heart spectral analysis as a marker for cardiac parasympathetic nerve lesions and in variation coefficient of heart rate variability. We could also show significantly reduced pupillary responses to cocaine 4% eye drops in patients with CAN as a test for sympathetic nerve alterations. The DAP of patients with CAN did not yield significant differences from the age matched controls. Patients without any systemic diabetic long term complication defined as CAN, peripheral sensomotor neuropathy, retinopathy, and nephropathy had no significant differences in their DAP compared to the probands.
Thus, it is of interest if patients in this study with CAN also significantly differ in their pupillary responses to cocaine, and if patients without CAN possibly have other diabetic long term complications or increased glycosylated haemoglobin levels, which may correlate with the small DAP.4
Nevertheless, this study by Cahill et al also clearly indicates that screening for pupillary dysfunction is mandatory as early as possible to prevent the sequelae of other autonomic neuropathic disorders.