Vision Impairment and Intracranial Pressure (VIIP) - 11.19.14
ISS Science for Everyone
Science Objectives for Everyone
The Vision Impairment and Intracranial Pressure (VIIP) project examined the effect of long-term exposure to microgravity on the structure of the eye along with change in distance and near vision of crew members before and after they returned to Earth.
Science Results for Everyone
I can see (less) clearly now. Many astronauts experience poorer vision after flight, some even for years after. A number of studies have looked for causes and distinct physical changes in the eye itself have been found. MRI scans suggest that pressure changes in the brain and spinal fluid caused by weightlessness may be partly to blame. Many astronauts do not show these effects, though, and more advanced imaging techniques may be needed to understand the role of changing brain pressure in microgravity. This in turn will help researchers assess vision problems and develop ways to prevent them.
Sponsoring Space Agency
National Aeronautics and Space Administration (NASA)
Human Exploration and Operations Mission Directorate (HEOMD)
ISS Expedition Duration
Previous ISS Missions
VIIP is a unique investigation which has not been performed for ISS crew members.
- Understanding physical and visual changes in the eyes of crew members will help researchers assess the reported impairments or any ocular trauma associated with long-term exposure to the microgravity environment.
- NASA has initiated several clinical and research protocols to acquire and analyze both retrospective and prospective preflight, inflight, and postflight data on all astronauts to define the exact origin of these potentially harmful vision changes.
- Potentially harmful effects of microgravity on the eye and optic nerve can be documented and better understood and possible preventive measures can be developed.
Complete eye examinations before and after long-duration space flight were completed for participating crew members using clinical opthalmic procedures such as manifest (no dilating agent) and/or cycloplegic (pupils are dilated with a chemical) refraction tests to determine refractive error, fundus (rear portion of the eye) photography to capture detailed images of retina along with associated blood vessels and nerves, noninvasive optical coherence tomography (OCT) imaging technology to capture high resolution retinal structures where the layers and thickness can be measured, direct imaging of the eye and optic nerver (ON) by magnetic resonance imaging (MRI) to determine eye globe geometry and axonal sheath thickness, lumbar punctures (LP) to measure the pressure of cerebrospinal fluid (CSF) in the space surrounding the spinal cord as a correlation to the intracranial and intraorbital pressure of the eye, visual acuity testing to document ability to focus images at a certain distance.
Also, approximately 300 astronauts were queried with vision questionaires to document changes during space missions.
Possible countermeasures may be developed to mitigate space-induced ocular impairments.
Before and after long-duration space opthalmic examinations of 7 crew members including cycloplegic and/or manifest refraction and fundus photography. Six underwent postmission retina optical coherence tomography (OCT) and magnetic resonance imaging (MRI). 4 had lumbar punctures (LP). Approximately 300 astronauts were queried regarding visual changes during space missions.
All activities were conducted preflight and postflight.
Since 1989, as part of the postflight eye examination, astronauts were queried as to whether they perceived a subjective improvement or degradation in distant or near vision (none, mild, moderate, or severe) during their short- and long-duration missions. Prompted by persistent reports of vision changes, NASA began a stepwise operational process to determine the c ause(s). Several ophthalmic procedures were initiated on astronauts, including dilated fundus (the rear portion of the eye) examinations with binocular ophthalmoscopy, cycloplegic refraction, optical coherence tomography (OCT), magnetic resonance imaging (MRI) of orbits, and fundus photography for before and after space missions.
In a follow-on study, twenty-seven astronauts underwent thin-section, three-dimensional, eye orbital, and conventional MRI brain scans. Eight astronauts underwent repeat imaging after an additional mission in space. All astronauts had previous exposure to microgravity. Image analysis of the optic nerve sheath, optic disc, posterior globe, and pituitary gland was performed and compared for association with intracranial evidence of excessive fluid buildup inside the skull, cells, tissues, or body cavities, venous blood clotting in the brain and/or mass lesion.
Visual acuity degradation in astronauts exposed to microgravity is a newly recognized phenomenon. Although the exact mechanism is yet to be fully determined, many MRI findings suggest that intracranial hypertension is an important component. However, a large proportion of astronauts do not show these ocular effects, suggesting there could be variable biologic response to the spaceflight environment and warrants a search for existing risk factors. Standardization of qualitative and quantitative imaging criteria will further help in the identification of asymptomatic changes and allow for the use of countermeasures to mitigate potential long-term vision damage. Future studies involving advance tissue imaging techniques would improve our understanding of the cause-versus-effect relationship of intracranial pressure after exposure to microgravity (Kramer 2012).
Zwart SR, Gibson CR, Mader TH, Ericson K, Ploutz-Snyder RJ, Heer MA, Heer MA, Heer MA, Smith SM, Smith SM. Vision Changes After Spaceflight Are Related to Alterations in Folate- and Vitamin B-12-Dependent One-Carbon Metabolism. Journal of Nutrition. 2012 Mar 1; 142(3): 427-431.
Mader TH, Gibson CR, Pass AF, Kramer LA, Lee AG, Fogarty J, Tarver WJ, Dervay JP, Hamilton DR, Sargsyan AE, Sargsyan AE, Phillips JL, Tran D, Lipsky W, Choi J, Stern C, Kuyumjian R, Polk JD. Optic Disc Edema, Globe Flattening, Choroidal Folds, and Hyperopic Shifts Observed in Astronauts after Long-duration Space Flight. Opthalmology. 2011; 118(10): 2058-2069. DOI: 10.1016/j.ophtha.2011.06.021. PMID: 21849212.
Kramer LA, Sargsyan AE, Sargsyan AE, Hasan KM, Polk JD, Hamilton DR. Orbital and Intracranial Effects of Microgravity: Findings at 3-T MR Imaging. Radiology. 2012; 263: 819-827. DOI: 10.1148/radiol.12111986.
Chylack Jr LT, Feiveson AH, Feiveson AH, Peterson LE, Tung WH, Wear , Marak LJ, Hardy DS, Chappell LJ, Cucinotta FA, Cucinotta FA. NASCA Report 2: Longitudinal Study of Relationship of Exposure to Space Radiation and Risk of Lens Opacity. Radiation Research. 2012; 178(1): 25-32. DOI: 10.1667/RR2876.1.
Ground Based Results Publications
Marshall-Bowman K, Barratt MR, Gibson CR. Ophthalmic Changes and Increased Intracranial Pressure Associated with Long Duration Spaceflight: An Emerging Understanding. Acta Astronautica. 2013; epub. DOI: 10.1016/j.actaastro.2013.01.014.
Wiener TC. Space Obstructive Syndrome: Intracranial Hypertension, Intraocular Pressure, and Papilledema in Space . Aviation, Space, and Environmental Medicine. 2012 January; 83(1): 64-66. DOI: 10.3357/ASEM.3083.2012.
Shinojima A, Iwasaki K, Aoki K, Ogawa Y, Yanagida R, Yuzawa M. Subfoveal Choroidal Thickness and Foveal Retinal Thickness During Head-Down Tilt. Aviation, Space, and Environmental Medicine. 2012 April; 83(4): 388-393. DOI: 10.3357/ASEM.3191.2012.
Berdahl JP, Yu DY, Morgan WH. The translaminar pressure gradient in sustained zero gravity, idiopathic intracranial hypertension, and glaucoma. Medical Hypotheses . 2012 December; 79(6): 719-724. DOI: 10.1016/j.mehy.2012.08.009. PMID: 22981592.