title: Relative flow volume, a novel blood flow index in the human retina derived from laser speckle flowgraphy.
abstract: OBJECTIVE
  We investigated the accuracy and reproducibility of relative flow volume (RFV), a novel index of blood flow in the human retina derived from laser speckle flowgraphy (LSFG).
  
  
  METHODS
  Pre- and postbranch retinal RFV measurements were compared in 34 retinal venous bifurcations in 34 healthy volunteers (mean age, 49.0 ± 14.8 years) to determine the accuracy of RFV. Next, the coefficient of variation (COV) of RFV was determined for 30 temporal retinal arteries in a second group of 18 healthy volunteers (mean age, 30.3 ± 7.7 years). Finally, laser Doppler velocimetry (LDV) data were obtained from the same study population and compared to RFV data from the retinal vessels.
  
  
  RESULTS
  A comparison of RFV measurements in a trunk vessel of the retina and the sum of its two daughter vessels revealed a strong correlation (r = 0.98, P < 0.001). Reproducibility analysis showed that the COV for RFV was 5.9% ± 3.6%. Linear regression analysis revealed that RFV was correlated significantly with LDV measurements of mean retinal blood velocity (vmean) and retinal blood flow (FLDV, vmean, r = 0.61, P < 0.001; FLDV, r = 0.51, P = 0.004, respectively), but not significantly correlated with ocular perfusion pressure (r = -0.04, P = 0.76).
  
  
  CONCLUSIONS
  These results suggest that RFV values obtained with LSFG can be considered an accurate and reliable index of relative blood flow in the human retina. Thus, RFV, a novel LSFG-derived variable, has potential for assessing retinal blood flow alterations in ocular disease.
authors.affiliation: Department of Ophthalmology, Tohoku University Graduate School of Medicine, Miyagi, Japan.
authors.forename: Yukihiro
authors.initials: Y
authors.lastname: Shiga
authors.affiliation: Department of Ophthalmology, Tohoku University Graduate School of Medicine, Miyagi, Japan.
authors.forename: Toshifumi
authors.initials: T
authors.lastname: Asano
authors.affiliation: Department of Ophthalmology, Tohoku University Graduate School of Medicine, Miyagi, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kunikata
authors.affiliation: Department of Ophthalmology, Tohoku University Graduate School of Medicine, Miyagi, Japan.
authors.forename: Fumihiko
authors.initials: F
authors.lastname: Nitta
authors.affiliation: Department of Ophthalmology, Tohoku Rosai Hospital, Miyagi, Japan.
authors.forename: Hajime
authors.initials: H
authors.lastname: Sato
authors.affiliation: Department of Ophthalmology, Tohoku University Graduate School of Medicine, Miyagi, Japan.
authors.forename: Toru
authors.initials: T
authors.lastname: Nakazawa
authors.affiliation: Department of Ophthalmology, NTT East Japan Tohoku Hospital, Miyagi, Japan Department of Ophthalmology, Tokyo Medical University, Hachioji Medical Center, Tokyo, Japan.
authors.forename: Masahiko
authors.initials: M
authors.lastname: Shimura
mesh_terms: D000328:Adult; D001783:Blood Flow Velocity / Q000502:physiology*; D001794:Blood Pressure; D001810:Blood Volume / Q000502:physiology*; D005260:Female; D006801:Humans; D007429:Intraocular Pressure; D017078:Laser-Doppler Flowmetry; D008297:Male; D008875:Middle Aged; D012039:Regional Blood Flow; D015203:Reproducibility of Results; D012160:Retina / Q000502:physiology*; D012161:Retinal Artery / Q000502:physiology*; D012169:Retinal Vein / Q000502:physiology*
keywords: laser speckle flowgraphy; ocular blood flow; relative flow volume; retinal blood flow