PURPOSE: Previous studies reported reduced aqueous humor flow through the a
nterior segment of the eye in patients with type 1 diabetes. This study inv
estigates whether reduced flow is the result of the diabetic state or of al
terations in glucose or insulin concentrations.
METHODS: A cross-sectional study, involving patients with type 1 diabetes a
nd healthy controls, measured aqueous flow at different insulin concentrati
ons. Eleven patients with type 1 diabetes (hemoglobin A1C = 7.0 +/- 0.3% [m
ean +/- SEM], normal < 6.5) with no microvascular complications and 17 cont
rols were prospectively studied. Controls were studied fasting and during a
hyperinsulinemic-euglycemic clamp (insulin 2 mU/kg per minute). Patients w
ith type 1 diabetes were similarly studied during two euglycemic clamp proc
edures (insulin 0.5 and 2.0 mU/kg per minute). Aqueous flow was measured by
fluorophotometry. Pulsatile ocular blood flow and intraocular pressure wer
e measured with a Langham flow probe.
RESULTS: Control subjects had no change in aqueous flow during fasting and
hyperinsulinemic conditions (3.0 <plus/minus> 0.1 vs 2.8 +/- 0.1 mul per mi
nute). In the patients with type 1 diabetes, aqueous flow was not decreased
with hyperinsulinemia, compared with the low insulin state (P = .7). Compa
red with control subjects, patients with type 1 diabetes had lower aqueous
flow during hyperinsulinemia (2.4 +/- 0.1 mul per minute, P = .03) and at l
ower insulin conditions (2.6 +/- 0.1 mul per minute, P < .05). No differenc
es in intraocular pressure or pulsatile ocular blood flow were noted betwee
n groups or between insulin states within groups.
CONCLUSIONS: Aqueous flow is decreased in patients with type 1 diabetes und
er euglycemic conditions of high and relatively low insulin concentrations,
despite the absence of microvascular complications. (Am J Ophthalmol 2001;
132:321-327. (C) 2001 by Elsevier Science Inc. All rights reserved.).