title: Measurements of Retinal Perfusion Using Laser Speckle Flowgraphy and Doppler Optical Coherence Tomography.
abstract: OBJECTIVE
  This study evaluated the validity of retinal perfusion measurements using laser speckle flowgraphy (LSFG) by means of in vitro experiments and direct comparison with dual-beam Doppler optical coherence tomography (D-OCT) in a healthy Caucasian population.
  
  
  METHODS
  The flow velocity of scattering solution pumped through a glass capillary was measured at 17 different flow velocities (range, 0.5-47 mm/s) using LSFG. The flow within the glass capillary was produced by a computer-controlled infusion pump. In vivo, three consecutive LSFG scans were obtained in 20 eyes of 20 healthy Caucasian subjects before and after pharmacological pupil dilation. Relative flow volume (RFV), the primary output parameter of LSFG, was comparatively validated relative to absolute measurements of retinal blood flow and velocity as obtained from D-OCT.
  
  
  RESULTS
  In the in vitro experiments, RFV was found to saturate at a level of approximately 700 arbitrary units (au) or 23.5 mm/s of actual velocity. In vivo, RFV was in significant agreement with absolute blood flow measurements as obtained from D-OCT in arteries (r = 0.69, P = 0.001) and veins (r = 0.74, P < 0.001). However, linear regression analysis revealed significant positive zero offset values for RFV of 223.4 and 282.7 au in arteries and veins, respectively.
  
  
  CONCLUSIONS
  Measurements of RFV were successfully obtainable, reproducible, and not influenced by pharmacological pupil dilation. Nevertheless, our data revealed flaws in the LSFG method of measuring retinal perfusion in Caucasians. Adjustment to the technique is required to address apparent issues with RFV, especially saturation effects with higher arterial flow rates. The present dataset may provide a valuable tool to do so. (Clinicaltrials.gov number NCT02582411).
authors.affiliation: Department of Clinical Pharmacology, Medical University of Vienna, Vienna, Austria 2Department of Ophthalmology, Kepler University Hospital, Linz, Austria 3University Eye Hospital, Ludwig-Maximilians University, Munich, Germany.
authors.forename: Nikolaus
authors.initials: N
authors.lastname: Luft
authors.affiliation: Department of Clinical Pharmacology, Medical University of Vienna, Vienna, Austria 4Department of Ophthalmology, Medical University of Warsaw, Warsaw, Poland.
authors.forename: Piotr A
authors.initials: PA
authors.lastname: Wozniak
authors.affiliation: Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria 6Institute of Applied Physics, Vienna University of Technology, Vienna, Austria.
authors.forename: Gerold C
authors.initials: GC
authors.lastname: Aschinger
authors.affiliation: Department of Clinical Pharmacology, Medical University of Vienna, Vienna, Austria.
authors.forename: Klemens
authors.initials: K
authors.lastname: Fondi
authors.affiliation: Department of Clinical Pharmacology, Medical University of Vienna, Vienna, Austria.
authors.forename: Ahmed M
authors.initials: AM
authors.lastname: Bata
authors.affiliation: Department of Clinical Pharmacology, Medical University of Vienna, Vienna, Austria.
authors.forename: René M
authors.initials: RM
authors.lastname: Werkmeister
authors.affiliation: Department of Clinical Pharmacology, Medical University of Vienna, Vienna, Austria 5Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria.
authors.forename: Doreen
authors.initials: D
authors.lastname: Schmidl
authors.affiliation: Department of Clinical Pharmacology, Medical University of Vienna, Vienna, Austria.
authors.forename: Katarzyna J
authors.initials: KJ
authors.lastname: Witkowska
authors.affiliation: Department of Ophthalmology, Kepler University Hospital, Linz, Austria.
authors.forename: Matthias
authors.initials: M
authors.lastname: Bolz
authors.affiliation: Department of Clinical Pharmacology, Medical University of Vienna, Vienna, Austria.
authors.forename: Gerhard
authors.initials: G
authors.lastname: Garhöfer
authors.affiliation: Department of Clinical Pharmacology, Medical University of Vienna, Vienna, Austria 5Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria 7Singapore Eye Research Institute, the Academia, Singapore 8Lee Kong Chian School of Medicine, Nanyang Technological University, Novena Campus, Singapore.
authors.forename: Leopold
authors.initials: L
authors.lastname: Schmetterer
mesh_terms: D000328:Adult; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D017078:Laser-Doppler Flowmetry / Q000379:methods*; D008297:Male; D011446:Prospective Studies; D012039:Regional Blood Flow / Q000502:physiology*; D015203:Reproducibility of Results; D012171:Retinal Vessels / Q000000981:diagnostic imaging / Q000502:physiology*; D041623:Tomography, Optical Coherence / Q000379:methods*