Spaceflight associated neuro-ocular syndrome

Ever wondered, what happens to the ocular health of astronauts in space?

A general pre and post health assessment will be done for astronauts to check for fitness. As it is a microgravity region, many of the organs in the upper body show significant changes. All these physiological and pathological changes in Astronauts observed in microgravity environment i.e., space is called Spaceflight associated neuro-ocular syndrome (SANS).


Accordingly, the ocular examination of SANS includes Tonometry, Fundus photography, Topography, A-Scan (Amplitude Scan), OCT(Optical coherence tomography)  and Cycloplegic refraction.

Spaceflight associated neuro-ocular syndrome ocular manifestations:

  • A sudden spike in IOP and
  • A shift in Refractive errors (Hyperopic shift)
  • Globe flattening
  • Optic disc oedema
  • Choroidal and retinal folds
  • Choroidal expansion
  • Cotton wool spots 

Why does this happen in space?

Due to free float in space, the Cephalid fluid of brain drains into its anterior part that includes head, neck and orbit, therefore that pressure leads to eye globe flattening. However, Physiology of Cephalid fluid in microgravity is yet to be known. In fact, further studies are required to understand aetiology for findings on long term Space missions.