A computational model for retinal haemodynamics under gravitational and postural variations.

Area of Science:

• Ophthalmology
• Aerospace Medicine
• Biomedical Engineering

Background:

• Spaceflight-associated neuro-ocular syndrome (SANS) poses risks to astronauts due to poorly understood retinal changes.
• Ocular circulation and intraocular pressure (IOP) are significantly affected by microgravity and postural shifts.

Purpose of the Study:

• To develop and validate a computational model simulating retinal haemodynamics under altered gravitational conditions.
• To investigate the mechanisms linking hydrostatic shifts, IOP changes, and retinal blood flow alterations relevant to SANS.

Main Methods:

• A lumped-parameter model was created, integrating a five-compartment retinal vascular network with a dynamic IOP module.
• Head-down tilt experiments were simulated to mimic microgravity-induced cephalad fluid shifts.
• Model outputs were validated against experimental data for IOP, ocular perfusion pressure, and retinal blood flow.

Main Results:

• Simulated IOP increased by 81% during head-down tilt, while ocular perfusion pressure remained stable.
• Retinal blood flow predictions aligned with in vivo Doppler measurements.
• The central retinal artery and arteriolar segments were identified as most vulnerable to mechanical stress.

Conclusions:

• The validated model provides mechanistic insights into SANS pathogenesis by integrating retinal and ocular biomechanics.
• It establishes quantitative thresholds for countermeasure development and aids in understanding terrestrial ocular disorders.
• The model serves as a transferable tool for studying glaucoma and hypertensive retinopathy.