Pupillography refines the diagnosis of diabetic autonomic neuropathy

Abstract

Although diabetic autonomic neuropathy involves most organs, diagnosis is largely based on cardiovascular tests. Light reflex pupillography (LRP) non-invasively evaluates pupillary autonomic function. We tested whether LRP demonstrates autonomic pupillary dysfunction in diabetics independently from cardiac autonomic neuropathy (CAN) or peripheral neuropathy (PN). In 36 type-II diabetics (39–84 years) and 36 controls (35–78 years), we performed LRP. We determined diameter (PD), early and late re-dilation velocities (DV) as sympathetic parameters and reflex amplitude (RA) and constriction velocity (CV) as parasympathetic pupillary indices. We assessed the frequency of CAN using heart rate variability tests and evaluated the frequency of PN using neurological examination, nerve conduction studies, thermal and vibratory threshold determination. Twenty-eight (77.8%) patients had abnormal pupillography results, but only 20 patients (56%) had signs of PN or CAN. In nine patients with PN, only pupillography identified autonomic neuropathy. Four patients had pupillary dysfunction but no CAN or PN. In comparison to controls, patients had reduced PD, late DV, RA and CV indicating sympathetic and parasympathetic dysfunction. The incidence and severity of pupillary abnormalities did not differ between patients with and without CAN or PN. LRP demonstrates sympathetic and parasympathetic pupillary dysfunction independently from PN or CAN and thus refines the diagnosis of autonomic neuropathy in type-II diabetics.