title: A method of quantifying retinal microvascular alterations associated with blood pressure and age.
abstract: OBJECTIVE
  To find an objective, sensitive method for quantifying microvascular alterations associated with level of blood pressure and age.
  
  
  METHODS
  A prospective cross-sectional study.
  
  
  METHODS
  Seventy-four previously untreated hypertensive patients, referred to a hospital outpatients department, and 26 normotensive volunteers participated. Twenty-four-hour ambulatory blood pressure monitoring and bilateral fundal photography were performed. The fundal photographs were projected on a screen such that the optic disc filled a circle of radius 5 cm. Microvessels crossing the border of a concentric circle of radius 20 cm were identified as arteriolar or venular, counted and their luminal diameters measured.
  
  
  METHODS
  Arteriolar and venular numbers, mean diameters and vascularities (arteriolar and venular vascularities defined as the sum of arteriolar and venular diameters, respectively).
  
  
  RESULTS
  The technique was reproducible. As blood pressure increased, arteriolar vascularity declined and venular vascularity increased. These associations resulted in a strong inverse correlation between blood pressure level and the ratio arteriolar vascularity: venular vascularity (r = 0.48, P < 0.001). Arteriolar number declined with increasing diastolic blood pressure (r = 0.22, P < 0.05). Mean arteriolar diameter appeared to have a U-shaped relationship with diastolic blood pressure levels (r = 0.27, P < 0.05). Venular dilation was associated with increasing blood pressure levels (r = 0.22, P < 0.05). Mean arteriolar and venular diameters declined significantly with age (r = 0.33 and 0.26, respectively; P < 0.01) and there was no association between arteriolar vascularity:venular vascularity ratio and age.
  
  
  CONCLUSIONS
  The method detected disparate retinal microvascular alterations with age and blood pressure. The arteriolar vascularity:venular vascularity ratio shows promise as a non-invasive, prognostic and therapeutic guide in hypertension.
authors.affiliation: Department of Clinical Pharmacology, Royal College of Surgeons in Ireland.
authors.forename: A V
authors.initials: AV
authors.lastname: Stanton
authors.forename: P
authors.initials: P
authors.lastname: Mullaney
authors.forename: F
authors.initials: F
authors.lastname: Mee
authors.forename: E T
authors.initials: ET
authors.lastname: O'Brien
authors.forename: K
authors.initials: K
authors.lastname: O'Malley
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D018660:Blood Pressure Monitoring, Ambulatory; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D006973:Hypertension / Q000503:physiopathology*; D008297:Male; D008833:Microcirculation / Q000502:physiology; D008875:Middle Aged; D015999:Multivariate Analysis; D011379:Prognosis; D011446:Prospective Studies; D015203:Reproducibility of Results; D012160:Retina / Q000503:physiopathology*