Inner ocular blood flow responses to an acute decrease in blood pressure in resting humans.

Area of Science:

• Ophthalmology
• Cardiovascular Physiology
• Ocular Circulation

Background:

• Autoregulation of blood flow is crucial for maintaining stable organ perfusion despite systemic pressure changes.
• The dynamic autoregulatory capacity of inner ocular vessels in response to acute hypotension remains incompletely understood.
• Assessing ocular vascular response to rapid blood pressure fluctuations is vital for understanding eye health.

Purpose of the Study:

• To evaluate the effectiveness of acute hypotension induced by thigh-cuff release in assessing dynamic autoregulation of ocular circulation.
• To investigate the autoregulatory response of retinal and choroidal blood flow to a sudden decrease in mean arterial blood pressure (MAP).

Main Methods:

• Utilized laser speckle flowgraphy to measure blood flow velocity in retinal arterioles and vasculature.
• Induced acute hypotension in 20 healthy subjects via rapid release of bilateral thigh occlusion cuffs.
• Calculated the ratio of relative changes in ocular blood flow velocity to relative changes in MAP.

Main Results:

• A significant decrease in MAP and blood flow velocity was observed in all measured ocular vessels immediately after cuff release.
• The ratio of relative change in inner ocular blood flow velocity to MAP exceeded 1% / %mmHg.
• The findings suggest a lack of explicit dynamic autoregulation in response to the induced acute hypotension.

Conclusions:

• The thigh-cuff release method did not demonstrate explicit dynamic autoregulation in the inner ocular vessels.
• Inner ocular vasculature appears susceptible to acute drops in systemic blood pressure.
• Further research is needed to fully elucidate the autoregulatory mechanisms of ocular circulation under dynamic conditions.