title: Optic nerve head blood flow autoregulation during changes in arterial blood pressure in healthy young subjects.
abstract: OBJECTIVE
  In the present study the response of optic nerve head blood flow to an increase in ocular perfusion pressure during isometric exercise was studied. Based on our previous studies we hypothesized that subjects with an abnormal blood flow response, defined as a decrease in blood flow of more than 10% during or after isometric exercise, could be identified.
  
  
  METHODS
  A total of 40 healthy subjects were included in this study. Three periods of isometric exercise were scheduled, each consisting of 2 minutes of handgripping. Optic nerve head blood flow was measured continuously before, during and after handgripping using laser Doppler flowmetry. Blood pressure was measured non-invasively in one-minute intervals. Intraocular pressure was measured at the beginning and the end of the measurements and ocular perfusion pressure was calculated as 2/3*mean arterial pressure -intraocular pressure.
  
  
  RESULTS
  Isometric exercise was associated with an increase in ocular perfusion pressure during all handgripping periods (p < 0.001). By contrast no change in optic nerve head blood flow was seen. However, in a subgroup of three subjects blood flow showed a consistent decrease of more than 10% during isometric exercise although their blood pressure values increased. In addition, three other subjects showed a consistent decline of blood flow of more than 10% during the recovery periods.
  
  
  CONCLUSIONS
  Our data confirm previous results indicating that optic nerve head blood flow is autoregulated during an increase in perfusion pressure. In addition, we observed a subgroup of 6 subjects (15%) that showed an abnormal response, which is in keeping with our previous data. The mechanisms underlying this abnormal response remain to be shown.
authors: Department of Clinical Pharmacology, Medical University of Vienna, Vienna, Austria ; Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria.
authors: Agnes
authors: A
authors: Boltz
authors: Reinhard
authors: R
authors: Told
authors: Katarzyna J
authors: KJ
authors: Napora
authors: Stefan
authors: S
authors: Palkovits
authors: René M
authors: RM
authors: Werkmeister
authors: Doreen
authors: D
authors: Schmidl
authors: Alina
authors: A
authors: Popa-Cherecheanu
authors: Gerhard
authors: G
authors: Garhöfer
authors: Leopold
authors: L
authors: Schmetterer
mesh_terms: D000328:Adult; D001794:Blood Pressure; D015444:Exercise; D005260:Female; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D007429:Intraocular Pressure; D017078:Laser-Doppler Flowmetry; D008297:Male; D009898:Optic Disk / Q000098:blood supply*; D055815:Young Adult