Corneal Edema and the Endothelium in Spaceflight

Area of Science:

• Ophthalmology
• Aerospace Medicine
• Space Physiology

Background:

• Future manned missions beyond low Earth orbit necessitate anticipating astronaut health risks, particularly concerning ophthalmology and ocular surface health.
• Corneal edema has been observed in mice during space missions due to increased stress response gene expression.

Purpose of the Study:

• To review current literature on corneal edema and endothelial function in the context of spaceflight.
• To identify mechanisms, treatments, and diagnostic modalities for spaceflight-related ocular surface anomalies.
• To inform strategies for enhancing astronaut visual function and mission safety.

Main Methods:

• A comprehensive literature search was performed using PubMed, Web of Science, and Embase databases.
• The search focused on ocular surface and spaceflight topics from inception to July 2024.
• Ninety-nine articles were included in the final review after initial screening of over 12,000 articles.

Main Results:

• Contact lens-related hypoxia was the most frequent mechanism (24%) contributing to corneal edema in spaceflight.
• Surgical grafts were the most common treatment (16.9%) for corneal edema.
• No significant differences in central corneal thickness were found pre- and postflight in astronauts with prior refractive surgery.

Conclusions:

• Understanding corneal edema and endothelial physiology is crucial for addressing ocular surface symptoms in astronauts.
• Anterior segment optical coherence tomography is a potential diagnostic tool for spaceflight.
• Implementing countermeasures can mitigate risks and improve visual function for human space exploration.