Correlation of the pilo-pupil ratio average, a new test for autonomic denervation, to the severity of diabetic retinopathy

Objective: To evaluate the associated between the degree of diabetic retinopathy and autonomic neuropathy, and to test whether ocular parasympathetic denervation is correlated to the degree of diabetic retinopathy. Design: Cross-sectional pilot study. Setting: The tertiary ophthalmic centre for the Atlantic provinces in Halifax. Patients: Twelve randomly selected patients (six women and six men with a mean age of 36.6 years) with insulin-dependent diabetes mellitus who had diabetic retinopathy. Outcome measures: Degree of diabetic retinopathy, hemoglobin A(1c) level, orthostatic change in systolic and diastolic blood pressure and in serum catecholamine levels, degree of pupillary supersensitivity to 0.125% pilocarpine (pilo-pupil ratio average [PPRA]). Results: The degree of diabetic retinopathy was significantly correlated with the duration of diabetes (p = 0.035), the hemoglobin A(1c) level (p = 0.004), the orthostatic change in diastolic blood pressure (p = 0.022) and the PPRA (p = 0.0007). Conclusions: The degree of diabetic retinopathy was significantly correlated with autonomic neuropathy and with the PPRA. Given these results, further study is indicated to determine whether autonomic neuropathy is a predictor of the severity of diabetic retinopathy.