Acute effects of insulin on aqueous humor flow in patients with type 1 diabetes.
OBJECTIVE
Previous studies reported reduced aqueous humor flow through the anterior segment of the eye in patients with type 1 diabetes. This study investigates whether reduced flow is the result of the diabetic state or of alterations in glucose or insulin concentrations.


METHODS
A cross-sectional study, involving patients with type 1 diabetes and healthy controls, measured aqueous flow at different insulin concentrations. Eleven patients with type 1 diabetes (hemoglobin A1C = 7.0 +/- 0.3% [mean +/- SEM], normal < 6.5) with no microvascular complications and 17 controls were prospectively studied. Controls were studied fasting and during a hyperinsulinemic-euglycemic clamp (insulin 2 mU/kg per minute). Patients with type 1 diabetes were similarly studied during two euglycemic clamp procedures (insulin 0.5 and 2.0 mU/kg per minute). Aqueous flow was measured by fluorophotometry. Pulsatile ocular blood flow and intraocular pressure were measured with a Langham flow probe.


RESULTS
Control subjects had no change in aqueous flow during fasting and hyperinsulinemic conditions (3.0 +/- 0.1 vs 2.8 +/- 0.1 microl per minute). In the patients with type 1 diabetes, aqueous flow was not decreased with hyperinsulinemia, compared with the low insulin state (P =.7). Compared with control subjects, patients with type 1 diabetes had lower aqueous flow during hyperinsulinemia (2.4 +/- 0.1 microl per minute, P =.03) and at lower insulin conditions (2.6 +/- 0.1 microl per minute, P <.05). No differences in intraocular pressure or pulsatile ocular blood flow were noted between groups or between insulin states within groups.


CONCLUSIONS
Aqueous flow is decreased in patients with type 1 diabetes under euglycemic conditions of high and relatively low insulin concentrations, despite the absence of microvascular complications.
Lane
J T
JT
Department of Internal Medicine, University of Nebraska Medical Center and Nebraska Health System, Omaha, NE 68198, USA. jtlane1@unmc.edu
Toris
C B
CB
Nakhle
S N
SN
Chacko
D M
DM
Wang
Y L
YL
Yablonski
M E
ME
D000328:Adult; D001082:Aqueous Humor / Q000378:metabolism*; D001786:Blood Glucose / Q000032:analysis; D003430:Cross-Sectional Studies; D003922:Diabetes Mellitus, Type 1 / Q000378:metabolism*; D005260:Female; D015590:Fluorophotometry; D015309:Glucose Clamp Technique; D006801:Humans; D006946:Hyperinsulinism / Q000378:metabolism*; D007328:Insulin / Q000008:administration & dosage* / Q000172:deficiency; D007429:Intraocular Pressure; D008297:Male; D011446:Prospective Studies
D001786:Blood Glucose; D007328:Insulin