title: Retinal vessel dilatation and elongation precedes diabetic macular oedema.
abstract: OBJECTIVE
  Retinal vessel dilatation is a well known phenomenon in diabetes. In this study, the theory of whether excessive changes in diameter and length of retinal vessels occur in the development of diabetic macular oedema was tested, supporting a hypothesis that the development of diabetic macular oedema may be linked to hydrostatic pressure changes described in Starling's law.
  
  
  METHODS
  From fundus photographs of diabetic patients attending a regular eye screening programme, the diameter and segment length of retinal vessels were measured in three retinopathy groups (12 patients each) with diabetic macular oedema (DMO), background retinopathy and no retinopathy, over a period of approximately 4 years, ending at the time of diagnosis of diabetic macular oedema in the DMO group.
  
  
  RESULTS
  A statistically significant dilatation and elongation of retinal arterioles, venules, and their macular branches was found before the diagnosis of macular oedema in the DMO group. No significant changes were found in the other two groups.
  
  
  CONCLUSIONS
  It is suggested that Starling's law applies to the formation of oedema in the retina as in other tissues.
authors.affiliation: Department of Ophthalmology, University of Iceland, Landakotsspítali, Reykjavik, Iceland.
authors.forename: J K
authors.initials: JK
authors.lastname: Kristinsson
authors.forename: M S
authors.initials: MS
authors.lastname: Gottfredsdóttir
authors.forename: E
authors.initials: E
authors.lastname: Stefánsson
mesh_terms: D000704:Analysis of Variance; D016022:Case-Control Studies; D003930:Diabetic Retinopathy / Q000473:pathology*; D004108:Dilatation, Pathologic; D018450:Disease Progression; D004487:Edema / Q000209:etiology; D006801:Humans; D006874:Hydrostatic Pressure; D008266:Macula Lutea; D008875:Middle Aged; D012171:Retinal Vessels / Q000473:pathology*