Acute effects of posture on intraocular pressure

• Type of Material: Article
• Authors: Emily S Nelson, NASA; Jerry G Myers, NASA; Beth E Lewandowski, NASA; Christopher Ethier, Emory University; Brian C Samuels, University of Alabama Birmingham
• Language: English
• Date: 2020-02-06
• Publisher: Public Library Science
• Publication Version: Final Published Version
• Copyright Statement: This is an open access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose.
• License: Creative Commons Universal : Public Domain Dedication
• Final Published Version (URL): http://dx.doi.org/10.1371/journal.pone.0226915
• Title of Journal or Parent Work: PLOS One
• Volume: 15
• Issue: 2
• Start Page: e0226915
• End Page: e0226915
• Grant/Funding Information: Research to Prevent Blindness provided a grant to the University of Alabama at Birmingham. This unrestricted funding from RPB is given to the authors' department to support research and research infrastructure.; NASA’s Human Research Program (http://www.nasa.gov/hrp) supported this work through the Cross-Cutting Computational Modeling Project and NASA grant numbers NNX13AP91G and NNX16AT06G.
• Keywords: NONCONTACT TONOMETRY; AGREEMENT; EPISCLERAL VENOUS-PRESSURE; Multidisciplinary Sciences; SUPINE; BODY POSITION; APPLANATION TONOMETRY; THICKNESS; Science & Technology; MIN; BLOOD; HEAD-DOWN TILT; Science & Technology - Other Topics

Abstract

Many experiments have documented the response of intraocular pressure (IOP) to postural change. External forces caused by gravitational orientation change produce a dynamic response that is encountered every day during normal activities. Tilting the body at a small downward angle is also relevant to studying the effects of hypogravity (spaceflight), including ocular changes. We examined data from 36 independent datasets from 30 articles on IOP response to postural change, representing a total population of 821 subjects (≥1173 eyes) with widely varying initial and final postures. We confirmed that IOP was well predicted by a simple quantity, namely the hydrostatic pressure at the level of the eye, although the dependence was complex (nonlinear). Our results show that posturally induced IOP change can be explained by hydrostatic forcing plus an autoregulatory contribution that is dependent on hydrostatic effects. This study represents data from thousands of IOP measurements and provides insight for future studies that consider postural change in relation to ocular physiology, intraocular pressure, ocular blood flow and aqueous humor dynamics.