Corneal Edema and the Endothelium in Spaceflight
INTRODUCTION: With future manned missions that extend beyond low Earth orbit, it would be wise to anticipate all risks to astronaut health, including those relevant to ophthalmology and the ocular surface. Corneal edema has been documented among mice experiments conducted onboard the Space Transportation System mission, STS-133, owing to increased stress response gene expression. METHODS: A targeted, relevant search of the literature on topics relating to ocular surface and spaceflight was conducted with scholarly databases PubMed, Web of Science, and Embase from inception to July 2024. RESULTS: From our search results we identified 12,742 articles, 485 of which met the scope of our initial literature search criteria. Following refinement, 99 articles were included in our review paper. The most frequently mentioned mechanisms of corneal edema related to spaceflight included contact lens related hypoxia (24%). Regarding treatments for corneal edema, surgical grafts (16.9%) were most common. From our data, central corneal thickness measurements in astronauts with prior refractive surgery showed no significant differences pre- and postflight: right eye mean preflight, 492 µm vs. postflight, 493.3 µm; left eye, 499 µm pre- and postflight. DISCUSSION: This knowledge may contribute to our understanding of the increased risk of ocular surface symptoms reported among astronauts. This review discusses the current literature on corneal endothelial transport physiology and the detriments of corneal edema to astronaut visual function. We also describe the diagnostic modalities we can apply to spaceflight, such as anterior segment optical coherence tomography, and offer convenient countermeasures to spaceflight-related ocular surface anomalies. In doing so, we aim to make future missions safer for human exploration. Lee R, Ong J, Sampige R, Panzo N, Memon H, Suh A, Waisberg E, Mader T, Berdahl J, Chévez-Barrios P, Lee AG. Corneal edema and the endothelium in spaceflight. Aerosp Med Hum Perform. 2025; 96(7):569–577.
Corneal epithelium histology taken from experimental mice aboard the STS-133 mission demonstrated corneal epithelium edema with acanthosis up to 7 d (R +7) following return. Under these conditions, the researchers speculated that this response was due to oxidative and inflammatory stress response gene expression. Created in BioRender.
AS-OCT is used to diagnose acute corneal keratoconus hydrops. A) Slit lamp examination of the cornea with corneal edema. B) AS-OCT with corneal edema. A reusable visual highlight under Creative Commons from Chong YJ, Azzopardi M, Hussain G, Recchioni A, Gandhewar J, Loizou C, Giachos I, Barua A, Ting DSJ. Clinical applications of anterior segment optical coherence tomography: an updated review. Diagnostics. 2024; 14(2):122. https://doi.org/10.3390/diagnostics14020122.86. Image: https://www.mdpi.com/diagnostics/diagnostics-14-00122/article_deploy/html/images/diagnostics-14-00122-g008.png.
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