Episode Details

Episode 151: Martian Medicine 102

Future Dr. Collins discussed with Dr. Arreaza two common complications of astronauts in a hypothetical travel to Mars: Spaceflight-Associated Neuro-ocular Syndrome and mental illness.  

Written by Wendy Collins, MSIV, Ross University School of Medicine. Comments by Hector Arreaza, MD.

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Arreaza: We are back for another episode of Martian Medicine! A couple months ago we published the episode Martian Medicine 101. We talked about radiation and its health risks for astronauts going beyond Low Earth Orbit such as a crew going to Mars. Today, we are going to be covering Martian Medicine 102, where we discuss some more risks from the article “Red risks for a journey to the red planet”. So, let’s just jump into it! The next risk we are going to talk about is Spaceflight-Associated Neuro-ocular Syndrome or SANS.  

Wendy: Yes, so this used to be called Vision Impairment Intracranial Pressure because the syndrome affects astronauts' eyes and vision and can appear like idiopathic intracranial hypertension. But the name changed to SANS because is not associated with the classic symptoms of increased intracranial pressure in idiopathic intracranial hypertension such as severe headaches, transient vision obscurations, double vision, and pulsatile tinnitus. Also, it has never induced vision changes that meet the definiti on of vision impairment, as defined by the National Eye Institute. Its name change also reflects that the syndrome can affect the CNS well beyond the retina and optic nerve. 

Arreaza: Let’s talk about SANS some more. SANS presents with an array of signs including edema of the optic disc and retinal nerve fiber, and what else?

Wendy: Edema of chorioretinal folds, globe flattening, and refractive error shifts. Flight duration is thought to play a role in the pathogenesis of SANS, as nearly all cases have been diagnosed during or immediately after long-duration spaceflight such as missions of 30 days duration or longer. But signs have been discovered as early as mission day 10. SANS has been studied in ISS crewmembers who are tested with optical coherence tomography (OCT), retinal imaging, visual acuity, a vision symptom questionnaire, Amsler grid, and ocular ultrasound.

Arreaza: About 69% of the US crewmembers on the ISS experience an increase in retinal thickness in at least one eye, indicating the presence of optic disc edema. This can cause an astronaut to experience blind spots and reduced visual function. Fortunately, to date, blind spots are uncommon and have not had an impact on mission performance.

Wendy: And chorioretinal folds if severe enough and located near the fovea, an astronaut can experience visual distortions or reduced visual acuity that cannot be corrected with glasses or contact lenses. Fortunately, and despite a prevalence of 15–20% in long-duration crewmembers, chorioretinal folds have not yet impacted astronauts’ visual performance during or after a mission.  

Arreaza: A change in your glasses prescription is due to a change in the distance between the cornea and the fovea, and it occurs in about 16% of crewmembers during long-duration spaceflight. This risk is reduced by giving crewmembers with several pairs of “Space Anticipation Glasses” (or contact lenses). The crewmember can then select the appropriate lenses to correct visual acuity. 

Wen