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Modeling the Effects of Spaceflight on the Posterior Eye in VIIPPurpose: Visual Impairment and Intracranial Pressure (VIIP) syndrome is a new and significant health concern for long-duration space missions. Its etiology is unknown, but is thought to involve elevated intracranial pressure (ICP)that induces connective tissue changes and remodeling in the posterior eye (Alexander et al. 2012). Here we study the acute biomechanical response of the lamina cribrosa (LC) and optic nerve to elevations in ICP utilizing finite element (FE) modeling. Methods: Using the geometry of the posterior eye from previous axisymmetric FE models (Sigal et al. 2004), we added an elongated optic nerve and optic nerve sheath, including the pia and dura. Tissues were modeled as linear elastic solids. Intraocular pressure and central retinal vessel pressures were set at 15 mmHg and 55 mmHg, respectively. ICP varied from 0 mmHg (suitable for standing on earth) to 30 mmHg (representing severe intracranial hypertension, thought to occur in space flight). We focused on strains and deformations in the LC and optic nerve (within 1 mm of the LC) since we hypothesize that they may contribute to vision loss in VIIP. Results: Elevating ICP from 0 to 30 mmHg significantly altered the strain distributions in both the LC and optic nerve (Figure), notably leading to more extreme strain values in both tension and compression. Specifically, the extreme (95th percentile) tensile strains in the LC and optic nerve increased by 2.7- and 3.8-fold, respectively. Similarly, elevation of ICP led to a 2.5- and 3.3-fold increase in extreme (5th percentile) compressive strains in the LC and optic nerve, respectively. Conclusions: The elevated ICP thought to occur during spaceflight leads to large acute changes in the biomechanical environment of the LC and optic nerve, and we hypothesize that such changes can activate mechanosensitive cells and invoke tissue remodeling. These simulations provide a foundation for more comprehensive studies of microgravity effects on human vision, e.g. to guide biological studies in which cells and tissues are mechanically loaded in a ranger elevant for microgravity conditions.
Document ID
20150011647
Acquisition Source
Glenn Research Center
Document Type
Presentation
Authors
Ethier, C. R.
(Georgia Inst. of Tech. Atlanta, GA, United States)
Feola, A. J.
(Georgia Inst. of Tech. Atlanta, GA, United States)
Raykin, J.
(Georgia Inst. of Tech. Atlanta, GA, United States)
Mulugeta, L.
(Universities Space Research Association Houston, TX, United States)
Gleason, R.
(Georgia Inst. of Tech. Atlanta, GA, United States)
Myers, J. G.
(NASA Glenn Research Center Cleveland, OH, United States)
Nelson, E. S.
(NASA Glenn Research Center Cleveland, OH, United States)
Samuels, B.
(Alabama Univ. Birmingham, AL, United States)
Date Acquired
June 26, 2015
Publication Date
May 3, 2015
Subject Category
Aerospace Medicine
Report/Patent Number
GRC-E-DAA-TN23060
Meeting Information
Meeting: The Association for Research in Vision and Ophthalmology (ARVO) 2015 Annual Meeting
Location: Denver, CO
Country: United States
Start Date: May 3, 2015
End Date: May 7, 2015
Sponsors: Association for Research in Vision and Ophthalmology
Funding Number(s)
WBS: WBS 516724.01.02.10
CONTRACT_GRANT: NNJ11HE31A
CONTRACT_GRANT: NNX13AP91G
Distribution Limits
Public
Copyright
Public Use Permitted.
Keywords
gravitational physiology
physiological response
biomechanics
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