Case File: Eye Changes on the Postflight Exam

What is this, and how common is it?

Spaceflight-associated neuro-ocular syndrome (SANS). It is a cluster of findings after long flights: optic disc swelling, posterior globe flattening, chorioretinal folds and a hyperopic shift [1][2]. NASA reports that about 70% of long-duration crew have at least one sign and about 18% are diagnosed with clinically concerning SANS [1]. To date, no permanent loss of vision has been reported [1]. All crew fly with glasses of increasing plus power for this reason [1].

Why does the preflight exam matter so much here?

SANS is defined by change from baseline. NASA performs a full preflight eye workup, including OCT, MRI and fundus photography, so that postflight findings can be compared [1]. Without a baseline, a mildly swollen disc or a small refraction change is hard to interpret. Request the agency or operator records.

Under NASA practice, would a lumbar puncture be considered?

Yes. NASA’s brief describes considering a postflight lumbar puncture when there is Frisén grade 1 or higher disc edema and/or an average peripapillary total retinal thickness increase of 55 µm or more on OCT in either eye. He meets both. An opening pressure of 25 cm H₂O or more prompts treatment consideration and review for future flight [1].

This is reported operational practice, shown for education. It is not an SMF recommendation.

What would make you think of a cause other than SANS?

• Severe or worsening headache, double vision (sixth-nerve palsy), pulsing tinnitus or fast-worsening vision: evaluate as you would any optic disc swelling, including imaging for a mass or venous sinus thrombosis. See SANS management.
• One-sided neck swelling or pain: jugular vein thrombosis has occurred in flight [3].
• SANS looks like idiopathic intracranial hypertension (IIH), but NASA notes the two share more differences than similarities. Intracranial pressure has never been measured in flight [1].