title: Noninvasive and direct monitoring of erythrocyte aggregates in human retinal microvasculature using adaptive optics scanning laser ophthalmoscopy.
abstract: OBJECTIVE
  To investigate erythrocyte aggregates in parafoveal capillaries by adaptive optics scanning laser ophthalmoscopy (AO-SLO).
  
  
  METHODS
  AO-SLO videos were acquired from the parafoveal areas of one eye in 10 healthy subjects. Erythrocyte aggregates were detected as "dark tails" that were darker regions than vessel shadows. The lengths of the dark tails were measured in target capillaries, and their time-dependent changes in length were analyzed using spatiotemporal images. The dark tail elongation rate was calculated as the change of dark tail length per unit length of the target capillary.
  
  
  RESULTS
  The overall average dark tail length was 112.1 ± 36.9 μm. The dark tail became longer in a time-dependent manner in every monitored capillary (P < 0.0001). The dark tail elongation rate and average velocity were 0.51 ± 0.37 and 1.49 ± 0.36 mm/s, respectively.
  
  
  CONCLUSIONS
  AO-SLO can be used for noninvasive and direct monitoring of blood dynamics in the retinal microvasculature without dying agents. Erythrocyte aggregates were detected as dark tails and were elongated in a time-dependent manner in the parafoveal capillaries of normal subjects. Monitoring the characteristics of dark tails has promising potential for evaluating retinal hemodynamics.
authors.affiliation: Department of Ophthalmology and Visual Sciences, Kyoto University Graduate School of Medicine, Kyoto, Japan.
authors.forename: Shigeta
authors.initials: S
authors.lastname: Arichika
authors.forename: Akihito
authors.initials: A
authors.lastname: Uji
authors.forename: Masanori
authors.initials: M
authors.lastname: Hangai
authors.forename: Sotaro
authors.initials: S
authors.lastname: Ooto
authors.forename: Nagahisa
authors.initials: N
authors.lastname: Yoshimura
mesh_terms: D000328:Adult; D001783:Blood Flow Velocity; D002196:Capillaries; D004912:Erythrocytes / Q000502:physiology*; D005584:Fovea Centralis / Q000098:blood supply*; D006801:Humans; D007834:Lasers; D009887:Ophthalmoscopy / Q000379:methods*; D012171:Retinal Vessels / Q000502:physiology*; D014741:Video Recording; D055815:Young Adult
keywords: AO-SLO; blood flow; dark tail; erythrocyte aggregates; parafoveal capillary