title: Retinal arterioles have impaired reactivity to hyperoxia in type 1 diabetes.
abstract: OBJECTIVE
  Diabetes has adverse effects on the retinal microvasculature. The purpose of this study was to compare the effects of inhalation of hypoxic, hyperoxic and normoxic-hypercapnic gas mixtures on retinal vessel diameter in people with and without diabetes.
  
  
  METHODS
  Sixty-one participants (aged 24-50 years) 29 with (male : female ratio 2.6 : 1) and 32 without (male : female ratio 0.7 : 1) diabetes, inhaled hypoxic, hyperoxic and normoxic-hypercapnic gas mixtures for 3-5 mins. The diameters of arterioles and venules were measured using digital retinal images taken before and after gas inhalation.
  
  
  RESULTS
  There was no significant difference in the diameters of arterioles and venules prior to gas inhalation in people with and without diabetes. Inhalation of the hyperoxic gas mixture caused a statistically significant decrease in arteriolar and venular diameters without altering mean arterial pressure significantly. Arteriolar vasoconstriction in response to the hyperoxic gas mixture was significantly reduced in people with diabetes (3.95% versus 7.75%; p = 0.04), but venular vasoconstriction did not differ significantly. A hypoxic gas mixture caused increased arteriolar and venular diameter and a normoxic-hypercapnic gas mixture had no significant effect on vessel diameter. Responses to hypoxic and normoxic-hypercapnic gas did not differ significantly between diabetes and non-diabetes subjects.
  
  
  CONCLUSIONS
  Type 1 diabetes impairs retinal arteriolar responses to hyperoxia. Abnormalities in retinal arteriolar reactivity in response to oxygen may play a role in the development of diabetic retinopathy and this technique may represent a simple means of identifying early abnormalities in the reactivity of retinal arterioles in diabetes.
authors.affiliation: Department of Ophthalmology, Odense University Hospital, Odense, Denmark. birgitte.larsen@ouh.fyns-amt.dk
authors.forename: Birgitte L
authors.initials: BL
authors.lastname: Justesen
authors.forename: Paresh
authors.initials: P
authors.lastname: Mistry
authors.forename: Nish
authors.initials: N
authors.lastname: Chaturvedi
authors.forename: Simon A
authors.initials: SA
authors.lastname: Thom
authors.forename: Nicholas
authors.initials: N
authors.lastname: Witt
authors.forename: Dennis
authors.initials: D
authors.lastname: Köhler
authors.forename: Alun D
authors.initials: AD
authors.lastname: Hughes
authors.forename: Anne Katrin
authors.initials: AK
authors.lastname: Sjølie
mesh_terms: D000328:Adult; D001160:Arterioles / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology; D002245:Carbon Dioxide / Q000008:administration & dosage; D003922:Diabetes Mellitus, Type 1 / Q000235:genetics / Q000503:physiopathology*; D004200:Diseases in Twins; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D018496:Hyperoxia / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000008:administration & dosage; D012042:Registries; D012161:Retinal Artery / Q000502:physiology*; D014661:Vasoconstriction; D055815:Young Adult
chemical_list: D002245:Carbon Dioxide; D010100:Oxygen