Issue 125 Item 10 Pupil Test Detects Future Autonomic Neuropathy in Diabetic Pat

Pupil tests may be one way of diagnosing [autonomic dysfunction] as early a possible. Diabetic patients, especially those with related complications, exhibit sympathetic denervation in the pupil, according to a report in the September issue of Diabetes Care. The cocaine eye-drop test can be used to rapidly assess sympathetic denervation.

Dr. Hendrik Lehnert, of Otto-von-Guericke-Universit t Magdeburg, Germany, and colleagues examined sympathetic pupillary responses in 47 type 1 diabetics with and without long-term complications and in 20 healthy controls. Long-term complications were defined as cardiac autonomic neuropathy (CAN), peripheral sensomotor neuropathy, retinopathy, and nephropathy.

The researchers measured horizontal pupil diameter at baseline and at defined time points after instilling eye drops containing 4% cocaine, 1% epinephrine, and 5% pholedrine.

Compared with controls, diabetic patients had significantly smaller pupil diameters (p = 0.011) before installation of the eye drops. Even in diabetic patients without CAN, initial horizontal pupil diameter was significantly smaller (3.43 mm) than in healthy subjects (3.98 mm, p = 0.004).

Maximal cocaine reaction was significantly diminished in patients with long-term complications (2.29 mm) compared with those without complications (3.13 mm; p < 0.001). Compared with healthy controls, diabetic patients without long-term complications showed no significant differences in pupillary responses.

No significant differences were observed in the epinephrine test, visual acuity, ocular pressure, and HbA1c between those with and without long-term complications.

The findings "suggest a mixed pre- and postganglionic dysfunction of the sympathetic plexus," Dr. Lehnert and colleagues surmise. "The significantly smaller horizontal pupil diameter in patients without CAN compared with that of healthy subjects could be a sign for early involvement of the pupil function before cardiac manifestation of systemic autonomic diabetic neuropathy."

As the researchers note, early neuropathy is reversible with intensive glycemic control. "Pupil tests may be one way of diagnosing [autonomic dysfunction] as early a possible." Diabetes Care 2002;25:1545-1550.