The impact of ocular hemodynamics and intracranial pressure on intraocular pressure during acute gravitational changes

Journal of Applied Physiology
Emily S NelsonC Ross Ethier

Abstract

Exposure to microgravity causes a bulk fluid shift toward the head, with concomitant changes in blood volume/pressure, and intraocular pressure (IOP). These and other factors, such as intracranial pressure (ICP) changes, are suspected to be involved in the degradation of visual function and ocular anatomical changes exhibited by some astronauts. This is a significant health concern. Here, we describe a lumped-parameter numerical model to simulate volume/pressure alterations in the eye during gravitational changes. The model includes the effects of blood and aqueous humor dynamics, ICP, and IOP-dependent ocular compliance. It is formulated as a series of coupled differential equations and was validated against four existing data sets on parabolic flight, body inversion, and head-down tilt (HDT). The model accurately predicted acute IOP changes in parabolic flight and HDT, and was satisfactory for the more extreme case of inversion. The short-term response to the changing gravitational field was dominated by ocular blood pressures and compliance, while longer-term responses were more dependent on aqueous humor dynamics. ICP had a negligible effect on acute IOP changes. This relatively simple numerical model shows promising predic...Continue Reading

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Citations

Jul 25, 2019·Investigative Ophthalmology & Visual Science·Omkar G KaskarLandon Grace
Feb 7, 2020·PloS One·Emily S NelsonBrian C Samuels
Jan 14, 2020·Experimental Eye Research·C Ross EthierJohn P Berdahl

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