Pupil
Test Detects Future Autonomic Neuropathy in Diabetic Patients
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.
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