This case study reports on an astronaut with previous post-flight ophthalmic abnormalities who developed more widespread choroidal folds and new-onset optic disc edema after a second long-duration mission.
They write that microgravity-induced anatomical changes that occurred during the first mission may have set the stage for recurrent or additional ocular changes during the second space flight.
While a number of ophthalmic findings, including optic disc edema, globe flattening and choroidal folds, have been observed in several astronauts after long-duration space flights, this is the first report of an astronaut with previously documented post-flight ophthalmic abnormalities who developed new pathological changes after a repeat long-duration mission.
The astronaut, a 57-year-old man, underwent a complete eye examination, including fundus photography, before and after his first long-duration space flight in 2003: a 161-day mission to the International Space Station (ISS). After this mission, he had ocular findings of choroidal folds inferior to the disc and a single cotton wool spot, both in the right eye.
Before and after his second long-duration flight, a 193-day mission to the ISS nine years later, he underwent fundus photography, optical coherence tomography, ocular ultrasonography and brain magnetic resonance imaging, as well as in-flight fundus photography and ultrasound. During this mission, in the same eye he developed more widespread choroidal folds and optic disc edema.
The authors propose three possible mechanisms to explain the ophthalmic findings, which they say are not mutually exclusive and may be multifactorial:
- the ocular changes resulted from increased intracranial pressure.
- the optic disc edema and other abnormalities are the result of localized events occurring at the level of the intracanalicular and intraorbital optic nerve that are independent of cerebrospinal fluid pressure.
- the optic disc edema observed is due to ocular hypotony.
Given the patient’s normal post-mission lumbar puncture opening pressure, the authors hypothesize that local ocular vascular or orbital optic nerve sheath changes associated with microgravity fluid shifts may have played a leading role in the etiology of the astronaut’s anomalies. They conclude that the ocular effects of repeat space travel may have been cumulative.
They say that continued pre-flight, in-flight and post-flight ophthalmic evaluation of astronauts will help determine the long-term clinical significance of these findings and whether the results seen in this astronaut are found in other repeat long-duration flyers.