Measurement of Choroidal blood flow in zero gravity

Ansari, Rafat R.; Suh, Kwang I.; Moret, Fabrice; Messer, Russell; Manuel, Francis K.

doi:10.1117/12.479427

Cited by 7 publications

(5 citation statements)

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“…Acute changes imposed by microgravity on humans can be studied during the roughly 20 s provided by parabolic flight, such as precipitous changes in central venous [ 68 ] and ocular pressures [ 20 ] and choroidal blood flow [ 69 ]. Other changes occur much more slowly and the effects may not be evident until after weeks or months of microgravity exposure, such as loss of bone [ 2 ] and muscle [ 3 ] mass.…”

Section: Fluid Redistribution In Microgravitymentioning

confidence: 99%

“…The choroid is the major supplier of blood to the ocular tissues. Within seconds, choroidal blood velocity increases in parabolic flight and its choroidal volume doubles [ 69 ]. Subfoveal choroidal thickness and IOP increased during acute (30-minute) 10° HDT, but there was no statistically significant change in retinal thickness [ 175 ].…”

Section: The Ocular Environment In Spaceflightmentioning

confidence: 99%

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Microgravity-Induced Fluid Shift and Ophthalmic Changes

Nelson

Mulugeta

Myers

2014

Life

115

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Although changes to visual acuity in spaceflight have been observed in some astronauts since the early days of the space program, the impact to the crew was considered minor. Since that time, missions to the International Space Station have extended the typical duration of time spent in microgravity from a few days or weeks to many months. This has been accompanied by the emergence of a variety of ophthalmic pathologies in a significant proportion of long-duration crewmembers, including globe flattening, choroidal folding, optic disc edema, and optic nerve kinking, among others. The clinical findings of affected astronauts are reminiscent of terrestrial pathologies such as idiopathic intracranial hypertension that are characterized by high intracranial pressure. As a result, NASA has placed an emphasis on determining the relevant factors and their interactions that are responsible for detrimental ophthalmic response to space. This article will describe the Visual Impairment and Intracranial Pressure syndrome, link it to key factors in physiological adaptation to the microgravity environment, particularly a cephalad shifting of bodily fluids, and discuss the implications for ocular biomechanics and physiological function in long-duration spaceflight.

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Section: Fluid Redistribution In Microgravitymentioning

confidence: 99%

Section: The Ocular Environment In Spaceflightmentioning

confidence: 99%

Microgravity-Induced Fluid Shift and Ophthalmic Changes

Nelson

Mulugeta

Myers

2014

Life

115

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“…The arterial and venous blood pressures at the eye are expected to be influenced by the changing gravitational environment and by posture. Unfortunately, there are conflicting data about what happens to blood pressure in parabolic flight, with some researchers observing distinct changes (3,41), while other studies indicate no change in MAP (39). To address these conflicting observations, we carried out simulations for both varying and constant MAPs.…”

Section: Methodsmentioning

confidence: 99%

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

Nelson

Mulugeta

Feola

et al. 2017

Journal of Applied Physiology

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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 predictive capability. To extend the model to more chronic conditions, additional data on longer-term autoregulation of blood and aqueous humor dynamics are needed. A significant percentage of astronauts present anatomical changes in the posterior eye tissues after spaceflight. Hypothesized increases in ocular blood volume and intracranial pressure (ICP) in space have been considered to be likely factors. In this work, we provide a novel numerical model of the eye that incorporates ocular hemodynamics, gravitational forces, and ICP changes. We find that changes in ocular hemodynamics govern the response of intraocular pressure during acute gravitational change.

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“…Medical imaging or physiology assessment Ultrasound with lower body negative pressure chamber 26 , Doppler flowmeter (head mounted) 27 , central venous pressure monitor 28 …”

Section: Surgical Carementioning

confidence: 99%

“…Newcomers to reduced gravity testing may also look to parabolic flight demonstrations unrelated to in vitro diagnostics when attempting to make device evaluation possible (or figuring out what is possible). Demonstrations from other previous medical or biological experimentation with well-documented flight preparation, in-flight strategies, and flight test equipment are included in Table 1 15, [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] . These may be informative due to inclusion of manual in-flight tasks, use of specialized equipment, and experimental containment.…”

Section: Introductionmentioning

confidence: 99%

Reduced-gravity Environment Hardware Demonstrations of a Prototype Miniaturized Flow Cytometer and Companion Microfluidic Mixing Technology

Phipps

Yin

Bae

et al. 2014

JoVE

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Until recently, astronaut blood samples were collected in-flight, transported to earth on the Space Shuttle, and analyzed in terrestrial laboratories. If humans are to travel beyond low Earth orbit, a transition towards space-ready, point-of-care (POC) testing is required. Such testing needs to be comprehensive, easy to perform in a reduced-gravity environment, and unaffected by the stresses of launch and spaceflight. Countless POC devices have been developed to mimic laboratory scale counterparts, but most have narrow applications and few have demonstrable use in an in-flight, reduced-gravity environment. In fact, demonstrations of biomedical diagnostics in reduced gravity are limited altogether, making component choice and certain logistical challenges difficult to approach when seeking to test new technology. To help fill the void, we are presenting a modular method for the construction and operation of a prototype blood diagnostic device and its associated parabolic flight test rig that meet the standards for flight-testing onboard a parabolic flight, reduced-gravity aircraft. The method first focuses on rig assembly for in-flight, reduced-gravity testing of a flow cytometer and a companion microfluidic mixing chip. Components are adaptable to other designs and some custom components, such as a microvolume sample loader and the micromixer may be of particular interest. The method then shifts focus to flight preparation, by offering guidelines and suggestions to prepare for a successful flight test with regard to user training, development of a standard operating procedure (SOP), and other issues. Finally, in-flight experimental procedures specific to our demonstrations are described. Video LinkThe video component of this article can be found at

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Measurement of Choroidal blood flow in zero gravity

Cited by 7 publications

References 0 publications

Microgravity-Induced Fluid Shift and Ophthalmic Changes

Microgravity-Induced Fluid Shift and Ophthalmic Changes

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

Reduced-gravity Environment Hardware Demonstrations of a Prototype Miniaturized Flow Cytometer and Companion Microfluidic Mixing Technology

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