Ocular outcomes evaluation in a 14-day head-down bed rest study

Giovanni Taibbi, Ronita L. Cromwell, Susana B. Zanello, Patrice O. Yarbough, Robert J. Ploutz-Snyder, Bernard F. Godley, Gianmarco Vizzeri

Research output: Contribution to journalArticle

15 Citations (Scopus)

Abstract

Introduction: We evaluated ocular outcomes in a 14-d head-down tilt (HDT) bed rest (BR) study designed to simulate the effects of microgravity on the human body. Methods: Healthy subjects were selected using NASA standard screening procedures. Standardized NASA BR conditions were implemented (e.g., strict sleep-wake cycle, standardized diet, 24-hour-a-day BR, continuous video monitoring). Subjects maintained a 6° HDT position for 14 consecutive days. Weekly ophthalmological examinations were performed in the sitting (pre/post-BR) and HDT (in-bed phase) positions. Equivalency tests with optimal-alpha techniques evaluated pre/post-BR differences in best-corrected visual acuity (BCVA), spherical equivalent, intraocular pressure (IOP), Spectral-domain OCT retinal nerve fiber layer thickness (RNFLT), optic disc and macular parameters. Results: 16 subjects (12 men and 4 women) were enrolled. Nearly all ocular outcomes were within our predefined clinically relevant thresholds following HDTBR, except near BCVA (pre/post-BR mean difference: -0.06 logMAR), spherical equivalent (-0.30 D), Tonopen XL IOP (+3.03 mmHg) and Spectralis OCT average (+1.14 m m), temporalinferior (+1.58 m m) and nasal-inferior RNFLT (+3.48 m m). Modified Amsler grid, red dot test, confrontational visual field, and color vision were within normal limits throughout. No changes were detected on stereoscopic color fundus photography. Discussion: A few functional and structural changes were detected after 14-d HDTBR, notably an improved BCVA possibly due to learning effect and RNFL thickening without signs of optic disc edema. In general, 6° HDTBR determined a small nonprogressive IOP elevation, which returned to baseline levels post- BR. Further studies with different BR duration and/or tilt angle are warranted to investigate microgravity-induced ophthalmological changes. Keywords: microgravity, intraocular pressure, retinal nerve fiber layer, optimal alpha.

Original languageEnglish
Pages (from-to)983-992
Number of pages10
JournalAviation Space and Environmental Medicine
Volume85
Issue number10
DOIs
StatePublished - 2014

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Bed Rest
Head
Head-Down Tilt
Intraocular Pressure
Weightlessness
Nerve Fibers
United States National Aeronautics and Space Administration
Visual Acuity
Color Vision
Papilledema
Visual Field Tests
Photography
Optic Disk
Human Body
Nose
Healthy Volunteers
Sleep
Color
Learning
Diet

Keywords

  • Intraocular pressure
  • Microgravity
  • Optimal alpha
  • Retinal nerve fiber layer

ASJC Scopus subject areas

  • Public Health, Environmental and Occupational Health

Cite this

Taibbi, G., Cromwell, R. L., Zanello, S. B., Yarbough, P. O., Ploutz-Snyder, R. J., Godley, B. F., & Vizzeri, G. (2014). Ocular outcomes evaluation in a 14-day head-down bed rest study. Aviation Space and Environmental Medicine, 85(10), 983-992. https://doi.org/10.3357/ASEM.4055.2014

Ocular outcomes evaluation in a 14-day head-down bed rest study. / Taibbi, Giovanni; Cromwell, Ronita L.; Zanello, Susana B.; Yarbough, Patrice O.; Ploutz-Snyder, Robert J.; Godley, Bernard F.; Vizzeri, Gianmarco.

In: Aviation Space and Environmental Medicine, Vol. 85, No. 10, 2014, p. 983-992.

Research output: Contribution to journalArticle

Taibbi, G, Cromwell, RL, Zanello, SB, Yarbough, PO, Ploutz-Snyder, RJ, Godley, BF & Vizzeri, G 2014, 'Ocular outcomes evaluation in a 14-day head-down bed rest study', Aviation Space and Environmental Medicine, vol. 85, no. 10, pp. 983-992. https://doi.org/10.3357/ASEM.4055.2014
Taibbi G, Cromwell RL, Zanello SB, Yarbough PO, Ploutz-Snyder RJ, Godley BF et al. Ocular outcomes evaluation in a 14-day head-down bed rest study. Aviation Space and Environmental Medicine. 2014;85(10):983-992. https://doi.org/10.3357/ASEM.4055.2014
Taibbi, Giovanni ; Cromwell, Ronita L. ; Zanello, Susana B. ; Yarbough, Patrice O. ; Ploutz-Snyder, Robert J. ; Godley, Bernard F. ; Vizzeri, Gianmarco. / Ocular outcomes evaluation in a 14-day head-down bed rest study. In: Aviation Space and Environmental Medicine. 2014 ; Vol. 85, No. 10. pp. 983-992.
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