title: Choroidal blood flow during isometric exercises.
abstract: OBJECTIVE
  To investigate the response of choroidal blood flow in the foveal region of the human eye to increases in mean perfusion pressure (PPm = mean ophthalmic artery pressure - intraocular pressure; IOP) induced by isometric exercises.
  
  
  METHODS
  Using laser-Doppler flowmetry, changes in velocity (ChBVel), number (ChBVol), and flux (ChBF) of red blood cells in the choroidal vascular system in the foveal region of the fundus were measured in both eyes of 11 normal subjects (ages 18 to 57 years) during isometric exercises.
  
  
  RESULTS
  During 90 seconds of squatting, PPm increased by an average of 67%, from 46 to 77 mm Hg. This resulted in a significant increase of 12% in ChBFm (the mean of ChBF during the heart cycle), mainly caused by an increase in ChBVelm. A further increase in PPm to a value approximately 85% above baseline resulted in a 40% increase in ChBFm. A significant negative correlation was found between the changes in ChBVelm and ChBVolm, during squatting.
  
  
  CONCLUSIONS
  Previous studies have demonstrated that during isometric exercise, blood pressures in the ophthalmic and brachial arteries rise in parallel. These observations and the current results indicate that an increase in PPm up to 67% induces an increase in choroidal vascular resistance that limits the increase in choroidal blood flow to approximately 12%. This regulatory process fails when PPm is further increased.
authors.affiliation: Institut de Recherche en Ophtalmologie, Sion, Switzerland.
authors.forename: C E
authors.initials: CE
authors.lastname: Riva
authors.forename: P
authors.initials: P
authors.lastname: Titze
authors.forename: M
authors.initials: M
authors.lastname: Hero
authors.forename: A
authors.initials: A
authors.lastname: Movaffaghy
authors.forename: B L
authors.initials: BL
authors.lastname: Petrig
mesh_terms: D000293:Adolescent; D000328:Adult; D001783:Blood Flow Velocity / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology; D001916:Brachial Artery / Q000502:physiology; D002829:Choroid / Q000098:blood supply*; D015444:Exercise / Q000502:physiology*; D005584:Fovea Centralis / Q000098:blood supply; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology; D017078:Laser-Doppler Flowmetry; D008297:Male; D008875:Middle Aged; D009880:Ophthalmic Artery / Q000502:physiology; D012680:Sensitivity and Specificity; D013564:Sympathetic Nervous System / Q000502:physiology