title: Methods for evaluation of retinal microvascular abnormalities associated with hypertension/sclerosis in the Atherosclerosis Risk in Communities Study.
abstract: OBJECTIVE
  To develop protocols to photograph and evaluate retinal vascular abnormalities in the Atherosclerosis Risk in Communities (ARIC) Study; to test reproducibility of the grading system; and to explore the relationship of these microvascular changes with blood pressure.
  
  
  METHODS
  Population-based, cross-sectional study.
  
  
  METHODS
  Among 4 examination centers, 11,114 participants (48-73 years of age) at their third triennial examination, after excluding persons with diabetes from this analysis.
  
  
  METHODS
  One eye of each participant was photographed by technicians with nonmydriatic fundus cameras. Reading center graders evaluated focal arteriolar narrowing, arteriovenous (AV) nicking, and retinopathy by examining slides on a light box and measured diameters of all vessels in a zone surrounding the optic disc on enhanced digitized images. To gauge generalized narrowing, vessel diameters were combined into central arteriolar and venular equivalents with formulas adjusting for branching, and the ratio of equivalents (A/V ratio) was calculated.
  
  
  METHODS
  Retinal vascular abnormalities, mean arteriolar blood pressure (MABP).
  
  
  RESULTS
  Among 11,114 participants, photographs were obtained of 99%, with quality sufficient to perform retinal evaluations in 81%. In the 9040 subjects with usable photographs, A/V ratio (lower values indicate generalized arteriolar narrowing) ranged from 0.57 to 1.22 (median = 0.84, interquartile range = 0.10), focal arteriolar narrowing was found in 7%, AV nicking in 6%, and retinopathy in 4%. Because of attrition of subjects and limitation of methods, prevalence of abnormality was likely underestimated. Controlling for gender, race, age, and smoking status, these retinal changes were associated with higher blood pressure. For every 10-mmHg increase in MABP, A/V ratio decreased by 0.02 unit (P < 0.0001), focal arteriolar narrowing had an odds ratio (OR) of 2.00 (95% confidence interval [CI] = 1.87-2.14), AV nicking had an OR of 1.25 (95% CI = 1.16-1.34), and retinopathy had an OR of 1.25 (95% CI = 1.15-1.37). For any degree of generalized narrowing, individuals with focal narrowing had MABP approximately 8 mmHg higher than those without (P < 0.0001). Masked replicate assessment of a sample found the following reproducibility: for A/V ratio, correlation coefficient = 0.79 and median absolute difference = 0.03; for focal arteriolar narrowing, kappa = 0.45; for AV nicking, kappa = 0.61; and for retinopathy, kappa = 0.89.
  
  
  CONCLUSIONS
  Protocols have been developed for nonmydriatic fundus photography and for evaluation of retinal vascular abnormalities. Several microvascular changes were significantly associated with higher blood pressure; follow-up will show whether these are predictive of later cerebrovascular or cardiovascular disease independently of other known risk factors.
authors.affiliation: ARIC Retinal Reading Center, Department of Ophthalmology & Visual Sciences, University of Wisconsin-Madison, 53705-2397, USA.
authors.forename: L D
authors.initials: LD
authors.lastname: Hubbard
authors.forename: R J
authors.initials: RJ
authors.lastname: Brothers
authors.forename: W N
authors.initials: WN
authors.lastname: King
authors.forename: L X
authors.initials: LX
authors.lastname: Clegg
authors.forename: R
authors.initials: R
authors.lastname: Klein
authors.forename: L S
authors.initials: LS
authors.lastname: Cooper
authors.forename: A R
authors.initials: AR
authors.lastname: Sharrett
authors.forename: M D
authors.initials: MD
authors.lastname: Davis
authors.forename: J
authors.initials: J
authors.lastname: Cai
mesh_terms: D000368:Aged; D001794:Blood Pressure; D002196:Capillaries / Q000473:pathology; D003324:Coronary Artery Disease / Q000150:complications* / Q000453:epidemiology; D003430:Cross-Sectional Studies; D003941:Diagnostic Techniques, Ophthalmological; D005260:Female; D005654:Fundus Oculi; D006801:Humans; D006973:Hypertension / Q000150:complications*; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008297:Male; D008875:Middle Aged; D010781:Photography / Q000379:methods; D015203:Reproducibility of Results; D012164:Retinal Diseases / Q000145:classification / Q000175:diagnosis* / Q000209:etiology; D012171:Retinal Vessels / Q000473:pathology*; D012307:Risk Factors; D012598:Sclerosis / Q000150:complications; D014481:United States / Q000453:epidemiology