title: Retinal blood flow in diabetic retinopathy.
abstract: OBJECTIVE
  (a) To report on the basic parameters of retinal blood flow in a population of diabetic patients with and without retinopathy and non-diabetic controls; (b) to formulate a haemodynamic model for the pathogenesis of diabetic retinopathy from this and other studies.
  
  
  METHODS
  Laser-Doppler velocimetry and computerised image analysis to determine retinal blood flow in a large cross sectional study.
  
  
  METHODS
  Diabetic retinopathy outpatient clinic.
  
  
  METHODS
  24 non-diabetic controls and 76 diabetic subjects were studied (63 patients with insulin dependent diabetes, 13 with non-insulin dependent diabetes). Of the diabetic subjects, 12 had no diabetic retinopathy, 27 had background retinopathy, 13 had pre-proliferative retinopathy, 12 had proliferative retinopathy, and 12 had had pan-retinal photocoagulation for proliferative retinopathy.
  
  
  METHODS
  Retinal blood flow (microliters/min) and conductance (rate of flow per unit of perfusion pressure).
  
  
  RESULTS
  In comparison with non-diabetic controls (9.52 microliters/min) and diabetic patients with no diabetic retinopathy (9.12 microliters/min) retinal blood flow was significantly increased in all grades of untreated diabetic retinopathy (background 12.13 microliters/min, pre-proliferative 15.27 microliters/min, proliferative 13.88 microliters/min). There was a significant decrease in flow after pan-retinal photocoagulation in comparison with all the other groups studied (4.48 microliters/min). Conductance of the retinal circulation was higher in the untreated diabetic retinopathy groups. These results were independent of age, sex, type of diabetes, duration of diabetes, glycated haemoglobin concentration, blood glucose concentration, blood pressure, and intraocular pressure.
  
  
  CONCLUSIONS
  Retinal blood flow is significantly increased in diabetic retinopathy in comparison with non-diabetic controls and diabetic subjects with no retinopathy. This has implications for controlling hypertension and hyperglycaemia as a strategy in reducing morbidity from diabetic retinopathy.
authors.affiliation: Department of Medicine, Royal Postgraduate Medical School, Hammersmith Hospital, London.
authors.forename: V
authors.initials: V
authors.lastname: Patel
authors.forename: S
authors.initials: S
authors.lastname: Rassam
authors.forename: R
authors.initials: R
authors.lastname: Newsom
authors.forename: J
authors.initials: J
authors.lastname: Wiek
authors.forename: E
authors.initials: E
authors.lastname: Kohner
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001783:Blood Flow Velocity / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology; D003430:Cross-Sectional Studies; D003920:Diabetes Mellitus / Q000503:physiopathology; D003930:Diabetic Retinopathy / Q000473:pathology / Q000503:physiopathology*; D005260:Female; D006439:Hemodynamics; D006801:Humans; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D012171:Retinal Vessels / Q000473:pathology / Q000503:physiopathology*; D014655:Vascular Resistance / Q000502:physiology