Ocular changes over 60 min in supine and prone postures.

Area of Science:

• Ophthalmology
• Space Medicine
• Human Physiology

Background:

• Astronauts experience ocular and visual changes after long space missions.
• Understanding the effects of altered gravity on the eye is crucial for space travel.
• Previous research suggests microgravity impacts ocular structures.

Purpose of the Study:

• To investigate the transient and sustained effects of gravity vector changes on ocular geometry and physiology.
• To analyze the impact of supine and prone body postures on intraocular pressure, ocular dimensions, and choroidal characteristics.
• To provide data informing the mechanisms behind spaceflight-induced ocular changes.

Main Methods:

• Ten healthy subjects (5 males, 5 females) participated.
• Ocular measurements (intraocular pressure, axial length, corneal thickness, aqueous depth, choroidal volume, and subfoveal thickness) were recorded over 60 minutes in supine and prone positions.
• Data were analyzed using repeated-measures analysis of covariance.

Main Results:

• In the prone position, intraocular pressure (IOP) and axial length increased significantly with time.
• Prone corneal thickness increased, while aqueous depth decreased over time.
• Supine posture led to a significant increase in choroidal volume over time.

Conclusions:

• Altering the direction of the gravity vector induces pronounced, time-dependent changes in ocular structures.
• These findings highlight the significant impact of gravitational forces on eye physiology.
• The study provides critical insights into ocular adaptations relevant to microgravity exposure.