title: Influence of flickering light on the retinal vessels in diabetic patients.
abstract: OBJECTIVE
  Stimulation of the retina with flickering light increases retinal vessel diameters in humans. Nitric oxide is a mediator of the retinal vasodilation to flicker. The reduction of vasodilation is considered an endothelial dysfunction. We investigated the response of retinal vessels to flickering light in diabetic patients in different stages of diabetic retinopathy.
  
  
  METHODS
  We studied 53 healthy volunteers, 68 type 1 diabetic patients, and 172 type 2 diabetic patients. The diameter of retinal vessels was measured continuously online with the Dynamic Vessel Analyzer (DVA). Diabetic retinopathy was classified using Early Treatment Diabetic Retinopathy Study criteria. Changes in vasodilation are expressed as percent change over baseline values.
  
  
  RESULTS
  After adjustments for age, sex, and antihypertensive treatment, the response of retinal arterioles to diffuse luminance flicker was significantly diminished in patients with type 1 diabetes compared with healthy volunteers. The vasodilation of retinal arterioles and venules decreased continuously with increasing stages of diabetic retinopathy. The retinal arterial diameter change was 3.6 +/- 2.1% in the control group, 2.6 +/- 2.5% in the no diabetic retinopathy group, 2.0 +/- 2.7% in the mild nonproliferative diabetic retinopathy (NPDR) group, 1.6 +/- 2.2% in the moderate NPDR group, 1.8 +/- 1.9% in severe NPDR group, and 0.8 +/- 1.6% in proliferative diabetic retinopathy group.
  
  
  CONCLUSIONS
  Flicker responses of retinal vessels are abnormally reduced in diabetic patients. This decreased response deteriorated with increasing stages of retinopathy. The response was already reduced before clinical appearance of retinopathy. The noninvasive testing of retinal autoregulation with DVA might prove to be of value in early detection of diabetic vessel pathological changes.
authors.affiliation: Department of Internal Medicine III, Friedrich-Schiller University, Bachstrasse 18, 07743, Jena, Germany. aleksandra.mandecka@med.uni-jena.de
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Mandecka
authors.forename: Jens
authors.initials: J
authors.lastname: Dawczynski
authors.forename: Marcus
authors.initials: M
authors.lastname: Blum
authors.forename: Nicolle
authors.initials: N
authors.lastname: Müller
authors.forename: Christoph
authors.initials: C
authors.lastname: Kloos
authors.forename: Gunter
authors.initials: G
authors.lastname: Wolf
authors.forename: Walthard
authors.initials: W
authors.lastname: Vilser
authors.forename: Heike
authors.initials: H
authors.lastname: Hoyer
authors.forename: Ulrich Alfons
authors.initials: UA
authors.lastname: Müller
mesh_terms: D000328:Adult; D000368:Aged; D001160:Arterioles / Q000503:physiopathology* / Q000528:radiation effects; D003922:Diabetes Mellitus, Type 1 / Q000503:physiopathology; D003930:Diabetic Retinopathy / Q000503:physiopathology*; D005260:Female; D005425:Flicker Fusion / Q000502:physiology*; D006801:Humans; D008027:Light; D008297:Male; D008875:Middle Aged; D018579:Patient Selection; D010775:Photic Stimulation; D011930:Reaction Time; D012016:Reference Values; D012171:Retinal Vessels / Q000503:physiopathology*; D014664:Vasodilation / Q000502:physiology*; D014786:Vision Disorders / Q000453:epidemiology / Q000503:physiopathology