title: Retinal blood flow in type 1 diabetic patients with no or mild diabetic retinopathy during euglycemic clamp.
abstract: OBJECTIVE
  To compare total retinal blood flow in diabetic patients with no or mild nonproliferative diabetic retinopathy and healthy control subjects and to investigate in patients whether there is a difference between retinal blood flow before morning insulin and under normoglycemic conditions using a glucose clamp.
  
  
  METHODS
  Twenty patients with type 1 diabetes with no or mild diabetic retinopathy were included in this open parallel-group study, and 20 healthy age- and sex-matched subjects were included as control subjects. Retinal blood flow was assessed by combining velocity measurements using laser Doppler velocimetry and diameter measurements using a commercially available dynamic vessel analyzer. Measurements were performed before and during a euglycemic clamp.
  
  
  RESULTS
  Total retinal blood flow was higher in diabetic patients (53 +/- 16 microl/min) than in healthy subjects (43 +/- 16 microl/min; P = 0.034 between groups). When plasma glucose in diabetic patients was reduced from 9.3 +/- 1.7 to 5.3 +/- 0.5 mmol/l (P < 0.001) retinal blood flow decreased to 49 +/- 15 microl/min (P = 0.0003 vs. baseline). Total retinal blood flow during the glucose clamp was not significantly different from blood flow in normal control subjects (P = 0.161).
  
  
  CONCLUSIONS
  Type 1 diabetic patients with no or only mild diabetic retinopathy have increased retinal blood flow before their morning insulin dosage. Blood flow is reduced toward normal during euglycemic conditions. Retinal blood flow may fluctuate significantly with fluctuating plasma glucose levels, which may contribute to the microvascular changes seen in diabetic retinopathy.
authors.affiliation: Department of Clinical Pharmacology, Medical University of Vienna, Vienna, Austria.
authors.forename: Berthold
authors.initials: B
authors.lastname: Pemp
authors.forename: Elzbieta
authors.initials: E
authors.lastname: Polska
authors.forename: Gerhard
authors.initials: G
authors.lastname: Garhofer
authors.forename: Michaela
authors.initials: M
authors.lastname: Bayerle-Eder
authors.forename: Alexandra
authors.initials: A
authors.lastname: Kautzky-Willer
authors.forename: Leopold
authors.initials: L
authors.lastname: Schmetterer
mesh_terms: D000328:Adult; D001783:Blood Flow Velocity / Q000502:physiology; D016022:Case-Control Studies; D003922:Diabetes Mellitus, Type 1; D003930:Diabetic Retinopathy / Q000503:physiopathology*; D005260:Female; D015309:Glucose Clamp Technique / Q000379:methods*; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D008297:Male; D012039:Regional Blood Flow / Q000502:physiology; D012171:Retinal Vessels / Q000502:physiology* / Q000503:physiopathology