Optic nerve sheath diameter and spaceflight: defining shortcomings and future directions

Area of Science:

• Space Medicine
• Ophthalmology
• Neuroscience

Background:

• Spaceflight-associated neuro-ocular syndrome (SANS) presents significant challenges for astronaut health during long-duration missions.
• Monitoring and preventing SANS are critical priorities in current space medicine research.

Purpose of the Study:

• To review existing literature on optic nerve sheath diameter (ONSD) measurements in the context of SANS.
• To identify and describe heterogeneity in ONSD measurement methodologies across 13 reviewed studies.
• To provide recommendations for standardizing ONSD assessment in future SANS research.

Main Methods:

• Systematic review of 13 studies investigating ONSD.
• Analysis of studies involving microgravity exposure or ground-based analogs (head-down tilt, dry immersion, animal models).
• Evaluation of ONSD as a proxy for elevated intracranial pressure in spaceflight contexts.

Main Results:

• ONSD measurement is a promising technique for detecting and quantifying neuro-ocular changes associated with spaceflight.
• Significant heterogeneity exists in imaging modalities, measurement techniques, and study designs within the current SANS literature.
• Variability in ONSD assessment methods may impact the reliability and comparability of findings.

Conclusions:

• Standardization of ONSD measurement protocols is essential for improving the accuracy and consistency of SANS detection and monitoring.
• Future research should focus on establishing uniform imaging and measurement techniques to reduce variability.
• Implementing standardized ONSD assessments will enhance our ability to manage neuro-ocular health in astronauts.