title: Effect of Diffuse Luminance Flicker Light Stimulation on Total Retinal Blood Flow Assessed With Dual-Beam Bidirectional Doppler OCT.
abstract: We assess the increase in total retinal blood flow (TRBF) induced by flicker stimulation of the human retina in vivo and investigate the flicker induced hyperemia by means of a vascular flow model of the retinal circulation to study neurovascular coupling (NC).
  
  
  
  In six healthy subjects, TRBF was measured before and during stimulation with diffuse luminance flicker. Blood flow velocities in retinal vessels were measured via dual-beam bidirectional Doppler Fourier-domain optical coherence tomography (FD-OCT), retinal vessel diameters were assessed based on FD-OCT phase data. This allowed for the calculation of TRBF before and during visual stimulation. Additionally, a mathematical flow model for the retinal vasculature was adapted to study the implications of diameter variations on retinal perfusion. Measured and simulated perfusion was compared to draw conclusions on the diameter variations in different layers of the vascular tree.
  
  
  
  The measured mean baseline flow was 36.4 ± 6.5 μl/min while the mean flow during flicker stimulation was 53.4% ± 8.3 μl/min. The individual increase in TRBF during flicker stimulation ranged between 34% and 66%. The average increase in TRBF over all measured subjects was 47.6% ± 12.6%.
  
  
  
  Dual-beam bidirectional Doppler FD-OCT allowed quantifying NC in the human retina in vivo and may be a promising method for monitoring alterations in NC caused by various pathologies. The comparison of the measured data with the results obtained in the simulated vasculature indicates that the vasodilation induced by NC is more pronounced in smaller vessels.
authors.affiliation: Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria 2Institute of Applied Physics, Vienna University of Technology, Vienna, Austria.
authors.forename: Gerold C
authors.initials: GC
authors.lastname: Aschinger
authors.affiliation: Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria 3Department of Clinical Pharmacology, Medical University of Vienna, Vienna, Austria 4Singapore Eye Research Institute, Singapore 5Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore.
authors.forename: Leopold
authors.initials: L
authors.lastname: Schmetterer
authors.affiliation: Department of Clinical Pharmacology, Medical University of Vienna, Vienna, Austria.
authors.forename: Klemens
authors.initials: K
authors.lastname: Fondi
authors.affiliation: Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria 2Institute of Applied Physics, Vienna University of Technology, Vienna, Austria.
authors.forename: Valentin
authors.initials: V
authors.lastname: Aranha Dos Santos
authors.affiliation: Department of Ophthalmology, Medical University of Graz, Graz, Austria.
authors.forename: Gerald
authors.initials: G
authors.lastname: Seidel
authors.affiliation: Department of Clinical Pharmacology, Medical University of Vienna, Vienna, Austria.
authors.forename: Gerhard
authors.initials: G
authors.lastname: Garhöfer
authors.affiliation: Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria.
authors.forename: René M
authors.initials: RM
authors.lastname: Werkmeister
mesh_terms: D000328:Adult; D001783:Blood Flow Velocity / Q000502:physiology* / Q000528:radiation effects; D005260:Female; D005425:Flicker Fusion / Q000502:physiology; D005583:Fourier Analysis; D006801:Humans; D017078:Laser-Doppler Flowmetry / Q000379:methods; D008297:Male; D008962:Models, Theoretical; D010775:Photic Stimulation / Q000379:methods; D012039:Regional Blood Flow / Q000502:physiology / Q000528:radiation effects; D012160:Retina / Q000503:physiopathology*; D012171:Retinal Vessels / Q000502:physiology*; D041623:Tomography, Optical Coherence / Q000379:methods; D014664:Vasodilation / Q000502:physiology