Microgravity-Induced Ocular Changes Assessed by Optical Coherence Tomography

Area of Science:

• Ophthalmology
• Aerospace Medicine
• Physiology

Background:

• Space missions risk astronaut visual health due to fluid shifts.
• Spaceflight-associated neuro-ocular syndrome (SANS) requires understanding.
• Head-down tilt (HDT) models microgravity's ocular effects.

Purpose of the Study:

• To review how HDT affects ocular parameters measured by optical coherence tomography (OCT).
• To assess changes in intraocular pressure (IOP) under HDT conditions.
• To understand the impact of HDT on retinal and choroidal thickness.

Main Methods:

• Systematic review of 7 databases through May 2025.
• Included studies on human subjects undergoing HDT with OCT outcomes.
• Assessed risk of bias using ROBINS-I v2.

Main Results:

• Mild HDT caused moderate IOP elevation and slight retinal thickening.
• Prolonged HDT led to cumulative retinal thickness and nerve fiber layer increases.
• Steeper tilts caused rapid IOP rises and choroidal thickness changes; recovery was often incomplete.

Conclusions:

• HDT-induced ocular changes confirm cephalad fluid shifts disrupt venous outflow.
• Findings support HDT as a model for microgravity-induced ocular effects.
• Standardized methodology and longer follow-up are needed for SANS research.