title: The source of moving particles in parafoveal capillaries detected by adaptive optics scanning laser ophthalmoscopy.
abstract: OBJECTIVE
  To investigate the source of moving particles in parafoveal capillaries detected by adaptive optics scanning laser ophthalmoscopy (AO-SLO).
  
  
  METHODS
  AO-SLO videos were acquired from the parafoveal areas of eyes of healthy subjects. The gray-scale values inside and outside the moving particles were measured and compared. Thereafter, successive frames of the captured videos were analyzed under higher magnification to detect changes in the gray values of bright spots inside the capillaries, before and during passage of the particles. Simultaneously, changes in the gray values of areas without the bright spots were measured for comparison. Then, the authors analyzed the packing arrangements of the bright spots in the particles, and measured the particle velocity using spatiotemporal images of the target capillary.
  
  
  RESULTS
  There were no significant differences in the gray values between the moving particles and the cone mosaic outside the parafoveal capillaries adjacent to the particles. The gray value of the bright spots in the dark shadow of the vessels increased when the particles passed through, while the dark areas without bright spots remained dark. There were no significant differences in the packing arrangements between the bright spots and surrounding cone mosaic. Further, the concordance rate of packing arrangements of bright spots between two consecutive moving particles in the capillary was 95.8%. The mean particle velocity was 1.34 ± 0.42 mm/s.
  
  
  CONCLUSIONS
  The particles moving in the capillaries are suggested to be reflections of photoreceptor aggregates that pass through circulating transparent objects such as leukocytes or plasma gaps.
authors.affiliation: Department of Ophthalmology and Visual Sciences, Kyoto University Graduate School of Medicine, Sakyo-ku, Kyoto, Japan. akihito1@kuhp.kyoto-u.ac.jp
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: Kohei
authors.initials: K
authors.lastname: Takayama
authors.forename: Naoko
authors.initials: N
authors.lastname: Arakawa
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Imamura
authors.forename: Koji
authors.initials: K
authors.lastname: Nozato
authors.forename: Nagahisa
authors.initials: N
authors.lastname: Yoshimura
mesh_terms: D000328:Adult; D002196:Capillaries / Q000166:cytology*; D004867:Equipment Design; D005584:Fovea Centralis / Q000098:blood supply* / Q000166:cytology; D006801:Humans; D007834:Lasers; D008875:Middle Aged; D009887:Ophthalmoscopy / Q000379:methods*; D055095:Optics and Photonics; D012016:Reference Values; D015203:Reproducibility of Results; D017949:Retinal Cone Photoreceptor Cells / Q000166:cytology*; D012171:Retinal Vessels / Q000166:cytology*