Prediction of Optic Disc Edema Progression During Spaceflight

Area of Science:

• Space Medicine
• Ophthalmology
• Astronaut Health

Background:

• Predicting optic disc edema (ODE) in astronauts is challenging, impacting resource allocation for monitoring and countermeasures.
• Identifying crewmembers at low risk for ODE can optimize mission resources and enable alternative activities.

Purpose of the Study:

• To determine if the magnitude of early in-flight ODE correlates with its magnitude later in a spaceflight mission.
• To establish if early in-flight OCT measurements can predict later ODE development.

Main Methods:

• A cohort study of International Space Station (ISS) crewmembers using optical coherence tomography (OCT) for imaging before, during, and after missions.
• Quantification of preflight and in-flight total retinal thickness (TRT) change (ΔTRT) as an objective measure of ODE.
• Analysis of ΔTRT at approximately 30 (FD30) and 150 (FD150) flight days using mixed-effects models.

Main Results:

• A strong association was found between FD30 ΔTRT and FD150 ΔTRT (correlation coefficient = 0.89, P < .001) in 43 ISS crewmembers.
• Crewmembers with ΔTRT < 20 μm on FD30 had a 2% probability of ΔTRT ≥ 55 μm on FD150.
• An optimal threshold of ΔTRT > 29 μm on FD30 predicted eyes at risk for ΔTRT ≥ 55 μm on FD150.

Conclusions:

• Astronauts showing no significant ODE by FD30 are unlikely to develop clinically concerning ODE by FD150.
• OCT imaging during spaceflight is a valuable tool for predicting the magnitude of ODE in longer missions.
• These findings can inform targeted monitoring and countermeasures for spaceflight-associated visual impairment.