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Choroidal blood flow during isometric exercises

C E Riva1, P Titze, M Hero

  • 1Institut de Recherche en Ophtalmologie, Sion, Switzerland.

Investigative Ophthalmology & Visual Science
|October 31, 1997
PubMed
Summary
This summary is machine-generated.

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Isometric exercise increases eye perfusion pressure, initially raising choroidal blood flow by 12%. However, further pressure increases overwhelm this system, indicating a failure in blood flow regulation.

Area of Science:

  • Ophthalmology
  • Cardiovascular Physiology
  • Human Physiology

Background:

  • Isometric exercise is known to increase systemic blood pressure.
  • Ophthalmic artery pressure and intraocular pressure (IOP) influence ocular hemodynamics.
  • Choroidal blood flow is crucial for retinal health and function.

Purpose of the Study:

  • To determine how choroidal blood flow in the foveal region responds to increased mean perfusion pressure (PPm) during isometric exercise.
  • To investigate the autoregulatory capacity of the choroidal vasculature under elevated PPm.

Main Methods:

  • Laser-Doppler flowmetry was used to measure red blood cell velocity (ChBVel), number (ChBVol), and flux (ChBF) in the foveal choroid.
  • Measurements were taken in 11 healthy subjects during isometric squatting exercises.

Related Experiment Videos

  • Mean perfusion pressure (PPm) was calculated as mean ophthalmic artery pressure minus IOP.

    • Main Results:

    • Squatting increased PPm by 67% (46 to 77 mm Hg), leading to a 12% rise in mean choroidal blood flux (ChBFm), primarily due to increased velocity (ChBVelm).
    • A further PPm increase (approx. 85% above baseline) resulted in a 40% increase in ChBFm.
    • A negative correlation was observed between changes in ChBVelm and ChBVolm during exercise.

    Conclusions:

    • Elevated PPm up to 67% induces increased choroidal vascular resistance, limiting choroidal blood flow increase to about 12%.
    • This autoregulatory mechanism appears to fail at higher PPm levels.
    • The findings suggest a limit to the eye's ability to regulate blood flow during significant physiological stress.