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[Blood flow measurement in the optic nerve head during isometric exercise]
A Movaffaghy1, C E Riva, B L Petrig
1Institut de Recherche en Ophtalmolgie, Sion.
Klinische Monatsblatter Fur Augenheilkunde
|July 25, 1998
Summary
This study demonstrates that optic nerve head blood flow autoregulation in humans remains stable despite increases in mean arterial pressure. Optic nerve blood flow is maintained even when blood pressure rises significantly.
Area of Science:
- Ophthalmology
- Physiology
- Cardiovascular Research
Context:
- Optic nerve head blood flow (Fonh) autoregulation is crucial for maintaining vision.
- Previous studies in animals and humans showed Fonh regulation with decreased perfusion pressure.
- The response of Fonh to increased perfusion pressure remained largely uncharacterized.
Purpose:
- To investigate the autoregulation of optic nerve head blood flow (Fonh) in response to an increase in systemic blood pressure.
- To quantify changes in Fonh, relative mean velocity (Velonh), and red blood cell flux (Volonh) during elevated blood pressure.
Summary:
- Laser Doppler flowmetry measured Fonh, Velonh, and Volonh in 13 healthy subjects during isometric squatting exercises.
- Squatting induced a significant increase in mean arterial pressure (MAP) and intraocular pressure (IOP).
- Despite a substantial rise in mean perfusion pressure (PPm) from 56 to 80 mm Hg, no significant changes in Fonh, Velonh, or Volonh were observed, indicating stable autoregulation.
Impact:
- This study provides the first direct evidence of optic nerve head blood flow autoregulation in humans during elevated systemic blood pressure.
- Findings suggest a robust autoregulatory mechanism protecting the optic nerve from hypertensive fluctuations.
- Understanding Fonh autoregulation is vital for managing ocular conditions affected by blood pressure variations.