Disproportionate pupillary involvement in diabetic autonomic neuropathy

To study the degree of pupillary impairment in diabetic and non-diabetic autonomic neuropathy.

We retrospectively sampled from all patients who underwent comprehensive autonomic testing and infrared pupillometry at UT Southwestern Medical Center. Composite autonomic severity score (CASS) and pupillary indices from the average of at least three pupillary response curves were recorded. We randomly matched patients with diabetic autonomic neuropathy (DAN) and patients with autonomic impairment unrelated to diabetes (non-DAN) based on gender, age (±5 years), and CASS (±1 point). We used the paired t test to analyze differences between the groups.

We identified 40 patients with DAN and 40 matched controls with non-DAN. M:F ratio was 1:1. Mean CASS was 4.2 and mean age was 62.4 years. Six had type I and the rest had type II diabetes mellitus. Both absolute constriction amplitude (ACA) and maximum constriction velocity (MCV) were significantly lower in DAN compared to non-DAN; mean ACA was 0.9 mm vs. 1.17 mm (p = 0.0077) and mean MCV was 2.8 vs. 3.6 mm/s (p = 0.0039). Severely diminished MCV for age was noted in 48 % of diabetic and in only 28 % of non-DAN patients. The ACA-corrected time to 75 % re-dilation was significantly delayed in DAN vs. non-DAN [mean 3.2 vs. 1.7 s/mm (p = 0.025)]. A statistically significant decline was noted for both the MCV and ACA with higher cardiovagal subscores among DAN patients.

Parasympathetic and sympathetic pupillary dysfunction appears to be a common feature of autonomic impairment in diabetes compared to non-diabetic causes of autonomic impairment.