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Updated: Dec 15, 2025

Assessment of Global Ocular Structure Following Spaceflight Using a Micro-Computed Tomography Micro-CT Imaging Method

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Published on: October 27, 2020

Optic Nerve Length before and after Spaceflight.

Anders Wåhlin¹, Petter Holmlund², Abigail M Fellows³

¹Department of Radiation Sciences, Umeå University, Umeå, Sweden; Umeå Center for Functional Brain Imaging, Umeå University, Umeå, Sweden.

|July 14, 2020

Summary

This summary is machine-generated.

Spaceflight causes optic nerve lengthening and forward eye movement in astronauts, potentially explaining spaceflight-associated neuro-ocular syndrome (SANS). Preflight body weight may be a risk factor for SANS.

Keywords:

Papilledema idiopathic intracranial hypertension intracranial pressure magnetic resonance imaging microgravity optic nerve space spaceflight-associated neuro-ocular syndrome

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Area of Science:

Ophthalmology
Space Medicine
Neuroscience

Background:

Spaceflight-associated neuro-ocular syndrome (SANS) presents with blurred vision and ocular changes in astronauts.
The underlying mechanisms of SANS, particularly the impact of microgravity on ocular structures, remain incompletely understood.

Purpose of the Study:

To investigate microgravity-induced deformations or movements of the eye and optic nerve.
To determine if these changes are associated with the development of SANS.

Main Methods:

A cohort study involving 22 astronauts undergoing space missions.
Pre- and post-flight MRI scans were analyzed to measure optic nerve length and optic nerve head (ONH) and optic chiasm (OC) displacement.

Main Results:

Optic nerve length increased significantly after spaceflight, primarily due to forward displacement of the ONH.
Forward ONH displacement correlated positively with mission duration, preflight body weight, and SANS clinical manifestations.
Upward displacement of the OC was observed but not linked to SANS.

Conclusions:

Spaceflight-induced optic nerve lengthening and ONH movement suggest SANS results from altered intracranial pressure.
Preflight body weight may be a risk factor for SANS.
Further research, including direct intracranial pressure measurement in space, is needed to confirm the SANS mechanism.