title: Retinal vascular and structural dynamics during acute hyperglycaemia.
abstract: OBJECTIVE
  To compare retinal vascular dynamics during acute hyperglycaemia in patients with type 2 diabetes and healthy volunteers.
  
  
  METHODS
  Twenty-one patients with type 2 diabetes and 27 healthy controls were examined with fundus photographic measurement of retinal vessel diameters, retinal oximetry, macular perfusion velocities and optical coherence tomographic measurement of subfoveal choroidal thickness every 30 min during a 3-hr 75 g oral glucose tolerance test (OGTT). Patients paused antidiabetic therapy for 1 week prior to the OGTT.
  
  
  RESULTS
  Plasma glucose (PG) and fluctuations in PG were larger in patients with diabetes (p < 0.0001). PG increased significantly 30 min after ingestion of glucose (p < 0.0001 in both groups). With a delay of 0-120 min, the PG increase was followed by increased retinal arterial oxygen saturations and arteriovenous oxygen saturation differences, narrowed retinal veins and increased arteriovenous diameter ratios. No effect of age, gender or diabetes status was observed. Choroidal thickness was transiently reduced in controls and unchanged in patients with diabetes (p = 0.021). Macular perfusion velocities increased after 150 min in patients with diabetes but not in controls (arterial p = 0.059; venous p = 0.16). Higher age and diabetes tended to be associated with higher retinal arterial oxygen saturation.
  
  
  CONCLUSIONS
  The transition from fasting to acute hyperglycaemia is followed, with a delay of up to 2 hr, by retinal vascular changes, notably increased oxygen extraction, suggesting an effect of secondary metabolic changes. Retinal responses were similar in patients with type 2 diabetes and controls despite differences in glucose levels. It is necessary to standardize measurement conditions in studies of retinal physiology.
authors.affiliation: Department of Ophthalmology, Glostrup Hospital, University of Copenhagen, Glostrup, Denmark.|Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Oliver N
authors.initials: ON
authors.lastname: Klefter
authors.affiliation: Center for Diabetes Research, Gentofte Hospital, University of Copenhagen, Hellerup, Denmark.
authors.forename: Tina
authors.initials: T
authors.lastname: Vilsbøll
authors.affiliation: Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.|Center for Diabetes Research, Gentofte Hospital, University of Copenhagen, Hellerup, Denmark.
authors.forename: Filip K
authors.initials: FK
authors.lastname: Knop
authors.affiliation: Department of Ophthalmology, Glostrup Hospital, University of Copenhagen, Glostrup, Denmark.|Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Michael
authors.initials: M
authors.lastname: Larsen
mesh_terms: D000208:Acute Disease; D000328:Adult; D000368:Aged; D001783:Blood Flow Velocity; D001786:Blood Glucose / Q000378:metabolism; D002829:Choroid / Q000473:pathology*; D003924:Diabetes Mellitus, Type 2 / Q000503:physiopathology*; D003930:Diabetic Retinopathy / Q000503:physiopathology*; D005260:Female; D005951:Glucose Tolerance Test; D064368:Healthy Volunteers; D006801:Humans; D006943:Hyperglycemia / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D010092:Oximetry; D010100:Oxygen / Q000097:blood; D012171:Retinal Vessels / Q000502:physiology*; D041623:Tomography, Optical Coherence; D014792:Visual Acuity; D055815:Young Adult
chemical_list: D001786:Blood Glucose; D010100:Oxygen
keywords: choroidal thickness; diabetes; diabetic retinopathy; hyperglycaemia; macular perfusion; retina; retinal oximetry; retinal vessel diameter