title: Dynamic responses in retinal vessel caliber with flicker light stimulation in eyes with diabetic retinopathy.
abstract: OBJECTIVE
  This study investigated the responses of retinal vessels to flickering light in diabetic patients with various stages of diabetic retinopathy (DR).
  
  
  METHODS
  This cross-sectional observational study evaluated adult subjects with diabetes mellitus. The Dynamic Vessel Analyzer (DVA) was used to measure retinal vascular dilatation in response to diffuse illuminance flicker. Diabetic retinopathy was graded from retinal photography.
  
  
  RESULTS
  There were 279 subjects in total, with a mean age of 59.9 ± 9.2 years. The majority were male (73%) and the mean HbA1c level and mean duration of diabetes were 7.7% ± 1.4% and 13.9 ± 10.4 years, respectively. After adjustments for age, sex, smoking, duration of diabetes, HbA1c, hypertension, and hyperlipidemia, the responses of both retinal arterioles and venules to flicker stimulation decreased continuously with increasing stages of diabetic retinopathy (P = 0.008 and <0.001, respectively). Subjects with reduced arteriolar dilation responses were more likely to have any DR (odds ratio, OR, 1.20, [95% confidence interval (CI), 1.01-1.45], P = 0.045, per SD decrease). Subjects with reduced venular dilation responses were more likely to have any DR, moderate DR, or vision-threatening DR (OR: 1.27 [1.04-1.53], P = 0.02; OR: 1.27 (1.06-1.49), P = 0.007; and OR: 1.51 (1.14-1.50), P = 0.002; per SD decrease, respectively).
  
  
  CONCLUSIONS
  The responses of retinal arterioles and venules to flickering light are reduced in subjects with DR, and decrease progressively with more severe stages of DR.
authors.affiliation: Singapore Eye Research Institute, Singapore National Eye Centre, Duke-NUS Graduate Medical School, Singapore Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
authors.forename: Laurence S
authors.initials: LS
authors.lastname: Lim
authors.affiliation: Cardiac Department, National University Heart Centre, Singapore Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
authors.forename: Lieng H
authors.initials: LH
authors.lastname: Ling
authors.affiliation: Singapore Eye Research Institute, Singapore National Eye Centre, Duke-NUS Graduate Medical School, Singapore.
authors.forename: Peng Guan
authors.initials: PG
authors.lastname: Ong
authors.affiliation: Singapore Eye Research Institute, Singapore National Eye Centre, Duke-NUS Graduate Medical School, Singapore.
authors.forename: Wallace
authors.initials: W
authors.lastname: Foulds
authors.affiliation: Singapore Eye Research Institute, Singapore National Eye Centre, Duke-NUS Graduate Medical School, Singapore Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
authors.forename: E Shyong
authors.initials: ES
authors.lastname: Tai
authors.affiliation: Singapore Eye Research Institute, Singapore National Eye Centre, Duke-NUS Graduate Medical School, Singapore.
authors.forename: Edmund
authors.initials: E
authors.lastname: Wong
authors.affiliation: Singapore Eye Research Institute, Singapore National Eye Centre, Duke-NUS Graduate Medical School, Singapore.
authors.forename: Shu Yen
authors.initials: SY
authors.lastname: Lee
authors.affiliation: Singapore Eye Research Institute, Singapore National Eye Centre, Duke-NUS Graduate Medical School, Singapore.
authors.forename: Doric
authors.initials: D
authors.lastname: Wong
authors.affiliation: Singapore Eye Research Institute, Singapore National Eye Centre, Duke-NUS Graduate Medical School, Singapore Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
authors.forename: Chui Ming Gemmy
authors.initials: CM
authors.lastname: Cheung
authors.affiliation: Singapore Eye Research Institute, Singapore National Eye Centre, Duke-NUS Graduate Medical School, Singapore Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
authors.forename: Tien Yin
authors.initials: TY
authors.lastname: Wong
mesh_terms: D000368:Aged; D001160:Arterioles / Q000503:physiopathology / Q000528:radiation effects; D003430:Cross-Sectional Studies; D003920:Diabetes Mellitus / Q000097:blood / Q000503:physiopathology*; D003930:Diabetic Retinopathy / Q000097:blood / Q000503:physiopathology*; D005260:Female; D006442:Glycated Hemoglobin / Q000378:metabolism; D006801:Humans; D008297:Male; D008875:Middle Aged; D010775:Photic Stimulation / Q000379:methods*; D012171:Retinal Vessels / Q000502:physiology / Q000528:radiation effects*; D014699:Venules / Q000503:physiopathology / Q000528:radiation effects
chemical_list: D006442:Glycated Hemoglobin
keywords: diabetic retinopathy; endothelial function; retinal vessels