Pupil size may indicate impending complications in people with diabetes. Researchers in Germany say that pupillary autonomic neuropathy may be an early sign of other autonomic nerve damage, such as that involving the heart. Autonomic neuropathy involves damage to the nerves in bodily systems that function automatically.
Forty-seven randomly selected people with type 1 diabetes were divided into groups based on whether or not they already had long-term diabetes-related complications. Researchers then compared the pupil size of these subjects with that of 20 subjects who did not have diabetes. Pupil size was measured at baseline and after instillation of eye drops containing medication known to affect pupil size.
Analysis of data showed significantly smaller pupil size before the instillation of eye drops in subjects with diabetes compared to subjects without diabetes. The cocaine eye drops produced a significantly diminished pupil reaction in those subjects with both diabetes and complications.
The researchers conclude that a decrease in horizontal pupil diameter could be an early indicator of systemic autonomic diabetic neuropathy and also that the cocaine eye drop test can rapidly assess autonomic nerve involvement in the eyes of people with diabetes.
—Diabetes Care, September 2002