Optic Disc Edema, Globe Flattening, Choroidal Folds, and Hyperopic Shifts Observed in Astronauts after Long-duration Space Flight

Mader, Thomas H.; Gibson, Charles R.; Pass, Anastas F.; Kramer, Larry A.; Lee, Andrew G.; Fogarty, Jennifer; Tarver, William J.; Dervay, Joseph P.; Hamilton, Douglas R.; Sargsyan, Ashot E.; Phillips, J. L.; Tran, Diana; Lipsky, William; Choi, Jun Shik; Stern, Claudia; Kuyumjian, Raffi; Polk, J. D.

doi:10.1016/j.ophtha.2011.06.021

Cited by 589 publications

(680 citation statements)

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“…1,13 Increased intracranial pressure, papilledema, globe flattening, dilated optic nerve sheaths, and visual disturbances have been described in both conditions (Table 2). 1,13,14 Although the etiologies of both conditions are unknown, researchers speculate that venous insufficiency or hypertension caused by cephalad fluid shifts during spaceflight are possible mechanisms for the VIIP syndrome in astronauts. Similarly, the pathophysiology of IIH is thought to be related to decreased CSF absorption at the arachnoid villi possibly due to venous-outflow obstruction.…”

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confidence: 98%

“…In the VIIP syndrome, none of the astronauts with ocular changes presented with clinical symptoms typical of IIH, including chronic headaches, diplopia, or transient visual obscurations. 1 Moreover, while IIH is typically a syndrome of female patients with obesity, 14 VIIP is more common in male astronauts. 1 Similarly, in our study of structural brain changes associated with long-term bed rest, we found important structural differences in our subjects from those previously described in patients with IIH.…”

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confidence: 99%

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Structural Brain Changes following Long-Term 6° Head-Down Tilt Bed Rest as an Analog for Spaceflight

Roberts

Zhu

Tabesh³

et al. 2015

AJNR Am J Neuroradiol

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Structural Brain Changes following Long-Term 6° Head-Down Tilt Bed Rest as an Analog for Spaceflight

Roberts

Zhu

Tabesh³

et al. 2015

AJNR Am J Neuroradiol

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“…For example, long-term exposure to a microgravity environment may simultaneously elevate ICP and IOP and cause visual impairment (Mader et al, 2011;Woo et al, 2012). During this condition, ICP and IOP are altered together.…”

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confidence: 99%

Pressure balance and imbalance in the optic nerve chamber: The Beijing Intracranial and Intraocular Pressure (iCOP) Study

Hou

Zheng

Yang

et al. 2016

Sci. China Life Sci.

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To determine the interdependence of intracranial pressure (ICP) and intraocular pressure (IOP) and how it affects optic nerve pressures, eight normal dogs were examined using pressure-sensing probes implanted into the left ventricle, lumbar cistern, optic nerve subarachnoid space in the left eye, and anterior chamber in the left eye. This allowed ICP, lumbar cistern pressure (LCP), optic nerve subarachnoid space pressure (ONSP) and IOP to be simultaneously recorded. After establishing baseline pressure levels, pressure changes that resulted from lowering ICP (via shunting cerebrospinal fluid (CSF) from the ventricle) were recorded. At baseline, all examined pressures were different (ICP>LCP>ONSP), but correlated (P<0.001). As ICP was lowered during CSF shunting, IOP also dropped in a parallel time course so that the trans-lamina cribrosa gradient (TLPG) remained stable (ICP-IOP dependent zone). However, once ICP fell below a critical breakpoint, ICP and IOP became uncoupled and TLPG changed as ICP declined (ICP-IOP independent zone). The optic nerve pressure gradient (ONPG) and trans-optic nerve pressure gradient (TOPG) increased linearly as ICP decreased through both the ICP-IOP dependent and independent zones. We conclude that ICP and IOP are coupled in a specific pressure range, but when ICP drops below a critical point, IOP and ICP become uncoupled and TLPG increases. When ICP drops, a rise in the ONPG and TOPG creates more pressure and reduces CSF flow around the optic nerve. This change may play a role in the development and progression of various ophthalmic and neurological diseases, including glaucoma. glaucoma, optic neuropathy, trans-lamina cribrosa pressure gradient (TLPG), trans-optic canal pressure gradient (TCPG), trans-optic nerve pressure gradient (TOPG), optic nerve pressure gradient (ONPG) Citation:

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“…As consequence, the optic nerve sheath distension, optic disc edema, vascular changes in the choroid and retina (eg., folds choroidal, thickening of the retinal fiber layer, cotton wool spots), "flattening" of the eyeball and a hyperopic shift have been described in several astronauts (3,8) . Still, a moderate acute IOP increase in the first moments in microgravity (probably due to congestion in the episcleral veins), followed by a steady IOP decrease were observed during longer periods under microgravity and in the post-flight evaluations (8,9) . On the other hand, these ocular changes displayed in microgravity conditions, and potentially related to increased ICP, could not be directly compared with similar terrestrial disorders, such as idiopathic intracranial hypertension, because some astronauts participating in long-term space flights have not reported any visual symptoms or showed any change in their ocular examinations.…”

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confidence: 99%

“…Thus, the neuroretinal-cerebrospinal fluid interface (including lamina cribrosa) could be affected by microgravity, due to the local "cul-de-sac" anatomy of the optic nerve head and the relative increased ICP transmitted to the eye by the subarachnoid space. As consequence, the optic nerve sheath distension, optic disc edema, vascular changes in the choroid and retina (eg., folds choroidal, thickening of the retinal fiber layer, cotton wool spots), "flattening" of the eyeball and a hyperopic shift have been described in several astronauts (3,8) . Still, a moderate acute IOP increase in the first moments in microgravity (probably due to congestion in the episcleral veins), followed by a steady IOP decrease were observed during longer periods under microgravity and in the post-flight evaluations (8,9) .…”

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confidence: 99%

Microgravity-induced ocular changes in astronauts: a sight odyssey

Paula¹,

Asrani²,

Rocha³

2016

Arquivos Brasileiros De Oftalmologia

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More than a new motivating force to the space race, the arrival of the American astronaut Scott Kelly from almost a year travel to the International Space Station promises a scientific milestone in the study of the long-term effects of the human body outside the Earth's atmosphere (1) . In addition to all the space-related data collected during the trip, the astronaut and his twin brother, Mark Kelly -nonparticipating to this mission, will be extensively compared. This study is analyzing laboratory samples from both, including assessments of the musculoskeletal, and immune system, genetic analysis and ocular evaluations, in order to increment knowledge related to microgravity effects on the human body. The results will be crucial for the Journey to Mars program (in 2030's) outlined in the bipartisan United State National Space Policy and National Aeronautics and Space Administration (NASA) Authorization Act issued in 2010.Microgravity is defined as a very small gravity condition in which objects appear to be weightless (2) . Given the difficulties and cost of space travel, parabolic flight tests (producing transient periods of microgravity) and the head-down bed-rest studies (simulating the pressure effects of microgravity) has been used to examine several systemic and ocular changes (3) . In addition to space radiation-induced cataract, the effects of microgravity on the eyes are considered the most impactful health problems for the success of long-term space travels. Still, a minimal comparison can be obtained by the experiences on high-altitude climbing, which have also shown harmful consequences to the retina, optic nerve, and cornea (mainly related to corneal refractive surgeries) (3)(4)(5) . As an analogy to the importance of vision-threatening environmental scenarios, the book "Into thin air" authored by Jon Krakauer quotes high-altitude-related blurred vision resulting in a Mount Everest tragedy as the critical limitation to an adventurer (6) . The first ocular findings in space flights were related to the blurring of vision, described in the 60's and later were associated with the Visual Impairment and Intracranial Pressure (VIIP) syndrome (3,7) . The findings outlined in this syndrome could be explained by modifications in the fluid shift pattern resulting from altered pressures in several liquid compartments of the body, especially the intraocular pressure (IOP), the intracranial pressure (ICP) and the blood pressure. Thus, the neuroretinal-cerebrospinal fluid interface (including lamina cribrosa) could be affected by microgravity, due to the local "cul-de-sac" anatomy of the optic nerve head and the relative increased ICP transmitted to the eye by the subarachnoid space. As consequence, the optic nerve sheath distension, optic disc edema, vascular changes in the choroid and retina (eg., folds choroidal, thickening of the retinal fiber layer, cotton wool spots), "flattening" of the eyeball and a hyperopic shift have been described in several astronauts (3,8) . Still, a moderate acute IOP increase in t...

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Optic Disc Edema, Globe Flattening, Choroidal Folds, and Hyperopic Shifts Observed in Astronauts after Long-duration Space Flight

Abstract: The authors have no proprietary or commercial interest in any of the materials discussed in this article.

Cited by 589 publications

References 47 publications

Structural Brain Changes following Long-Term 6° Head-Down Tilt Bed Rest as an Analog for Spaceflight

Structural Brain Changes following Long-Term 6° Head-Down Tilt Bed Rest as an Analog for Spaceflight

Pressure balance and imbalance in the optic nerve chamber: The Beijing Intracranial and Intraocular Pressure (iCOP) Study

Microgravity-induced ocular changes in astronauts: a sight odyssey

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