Intraocular Pressure in Microgravity

Mader, Thomas H.

doi:10.1002/j.1552-4604.1991.tb03654.x

Cited by 20 publications

(15 citation statements)

References 3 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This was further corroborated by Spacelab experiments that showed mean IOP rise of 20%–25% during flight, and a decrease below baseline levels postflight [ 17 , 18 ]. Similar investigations were conducted during Shuttle missions and in microgravity analog environments that also confirmed the IOP increase during acute exposure [ 7 , 19 , 20 , 21 , 22 , 23 , 24 ]. Overall, the ophthalmic changes were minor or transient, without other symptoms or clinical findings, and were not uncommon in the broader 40 to 50 year-old population.…”

Section: The Visual Impairment and Intracranial Pressure (Viip) Sysupporting

confidence: 66%

Microgravity-Induced Fluid Shift and Ophthalmic Changes

Nelson

Mulugeta

Myers

2014

Life

121

View full text Add to dashboard Cite

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.

show abstract

Section: The Visual Impairment and Intracranial Pressure (Viip) Sysupporting

confidence: 66%

Microgravity-Induced Fluid Shift and Ophthalmic Changes

Nelson

Mulugeta

Myers

2014

Life

121

View full text Add to dashboard Cite

show abstract

“…visual impairment and intracranial pressure; intraocular pressure; choroidal area; hydrostatic gradient UNDERSTANDING THE IMMEDIATE response of the eye to alterations in the gravity vector is important because it likely initiates the ocular adaptation to prolonged microgravity exposure. Compared with both the upright and supine positions on Earth, intraocular pressure (IOP) is increased initially upon entering microgravity (6,9,10,21,22; Draeger J., personal communication). IOP increases 50 -90% shortly after entering microgravity (11,21).…”

mentioning

confidence: 99%

Acute effects of changes to the gravitational vector on the eye

Anderson

Swan

Phillips

et al. 2016

Journal of Applied Physiology

View full text Add to dashboard Cite

Intraocular pressure (IOP) initially increases when an individual enters microgravity compared with baseline values when an individual is in a seated position. This has been attributed to a headward fluid shift that increases venous pressures in the head. The change in IOP exceeds changes measured immediately after moving from seated to supine postures on Earth, when a similar fluid shift is produced. Furthermore, central venous and cerebrospinal fluid pressures are at or below supine position levels when measured initially upon entering microgravity, unlike when moving from seated to supine postures on Earth, when these pressures increase. To investigate the effects of altering gravitational forces on the eye, we made ocular measurements on 24 subjects (13 men, 11 women) in the seated, supine, and prone positions in the laboratory, and upon entering microgravity during parabolic flight. IOP in microgravity (16.3 ± 2.7 mmHg) was significantly elevated above values in the seated (11.5 ± 2.0 mmHg) and supine (13.7 ± 3.0 mmHg) positions, and was significantly less than pressure in the prone position (20.3 ± 2.6 mmHg). In all measurements,P< 0.001. Choroidal area was significantly increased in subjects in a microgravity environment (P< 0.007) compared with values from subjects in seated (increase of 0.09 ± 0.1 mm(2)) and supine (increase of 0.06 ± 0.09 mm(2)) positions. IOP results are consistent with the hypothesis that hydrostatic gradients affect IOP, and may explain how IOP can increase beyond supine values in microgravity when central venous and intracranial pressure do not. Understanding gravitational effects on the eye may help develop hypotheses for how microgravity-induced visual changes develop.

show abstract

“…The current models used to explain the physiological effects of gravity changes are focused on the hydrostatic column effects. [2][3][4][5] That is, under microgravity, cephalad shift of intravascular and extravascular body fluids results in the rise in episcleral venous pressure leading to an increased outflow resistance of the aqueous humor and elevation of IOP. In several studies under microgravity and simulated microgravity, 2,4,6-10 IOP increased 20% to 114% depending on the duration of exposure to microgravity.…”

mentioning

confidence: 99%