Related Experiment Video
Updated: May 28, 2026

Translaminar Autonomous System Model for the Modulation of Intraocular and Intracranial Pressure in Human Donor Posterior Segments
Published on: April 24, 2020
Diurnal pattern of intraocular pressure is affected by microgravity when measured in space with the pressure
Ki-Young Chung1, Se Joon Woo, Soyeon Yi
1School of Military Medicine, AFMC, Daejeon, Seoul National University College of Medicine, Seoul National University Bundang Hospital, Seongnam, Korea. spacechung@hotmail.com
Purpose:
This study was designed to evaluate the effect of microgravity on the diurnal variation of intraocular pressure (IOP).
Methods:
IOPs were measured with the pressure phosphene tonometer in 1 subject (the first Korean astronaut) during spaceflight. IOPs were measured every 3 hours during day time (6 times per day) at 2 separate days in space with 3 repeated measurements at each time on both eyes. A total of 72 measurements were obtained during spaceflight. To obtain control IOP data, IOP was measured using the same protocol on ground before spaceflight.
Results:
Mean IOP increased by 26.3% during spaceflight compared with that on ground [16.47 ± 0.60 (SD) mm Hg vs. 13.04 ± 0.74 mm Hg, P<0.001). The IOP elevation was maintained until Launch+8 days. There was no significant difference in IOP increase between right and left eyes (16.4 2 ± 0.65 mm Hg right eye vs. 16.53 ± 0.56 mm Hg left eye). There was a different pattern of diurnal variation of IOP during spaceflight compared with that on ground. The IOP at 7 AM was the lowest under microgravity, whereas it was the highest on ground. The slope of the best fit line for diurnal IOP measures was 0.0349 mm Hg/h (95% confidence interval: 0.0082-0.0616) under microgravity and -0.0294 mm Hg/h (95% confidence interval: -0.0063-0.0041) on ground.
Conclusions:
The study showed a different diurnal pattern of IOP under microgravity compared with that on ground. This result suggests that gravity and subsequent body fluid shift is one of the determining factors of IOP diurnal variation.
Related Concept Videos
Increased Intracranial Pressure l: Introduction
Glaucoma: Overview
Increased Intracranial Pressure ll: Pathophysiology
Open Angle Glaucoma: Treatment
Drugs such as carbonic anhydrase inhibitors, α2- and...
Variation of Atmospheric Pressure
Assuming the air temperature is constant at a given altitude and that the ideal gas law of thermodynamics describes the atmosphere to a good approximation, one can find the variation of atmospheric pressure with height.
Let p(y) be the atmospheric pressure at...
Measurement of Blood Pressure

