Related Experiment Video
Updated: Aug 10, 2026

Trabecular Meshwork Response to Pressure Elevation in the Living Human Eye
Published on: June 20, 2015
The effect of prone positioning on intraocular pressure in anesthetized patients
M A Cheng1, A Todorov, R Tempelhoff
1Department of Anesthesiology, Washington University School of Medicine, St Louis, Missouri, USA. chengm@notes.wustl.edu
Background:
Ocular perfusion pressure is commonly defined as mean arterial pressure minus intraocular pressure (IOP). Changes in mean arterial pressure or IOP can affect ocular perfusion pressure. IOP has not been studied in this context in the prone anesthetized patient.
Methods:
After institutional human studies committee approval and informed consent, 20 patients (American Society of Anesthesiologists physical status I-III) without eye disease who were scheduled for spine surgery in the prone position were enrolled. IOP was measured with a Tono-pen XL handheld tonometer at five time points: awake supine (baseline), anesthetized (supine 1), anesthetized prone (prone 1), anesthetized prone at conclusion of case (prone 2), and anesthetized supine before wake-up (supine 2). Anesthetic protocol was standardized. The head was positioned with a pinned head-holder. Data were analyzed with repeated-measures analysis of variance and paired t test.
Results:
Supine 1 IOP (13 +/- 1 mmHg) decreased from baseline (19 +/- 1 mmHg) (P < 0.05). Prone 1 IOP (27 +/- 2 mmHg) increased in comparison with baseline (P < 0.05) and supine 1 (P < 0.05). Prone 2 IOP (40 +/- 2 mmHg) was measured after 320 +/- 107 min in the prone position and was significantly increased in comparison with all previous measurements (P < 0.05). Supine 2 IOP (31 +/- 2 mmHg) decreased in comparison with prone 2 IOP (P < 0.05) but was relatively elevated in comparison with supine 1 and baseline (P < 0.05). Hemodynamic and ventilatory parameters remained unchanged during the prone period.
Conclusions:
Prone positioning increases IOP during anesthesia. Ocular perfusion pressure could therefore decrease, despite maintenance of normotension.
Related Concept Videos
Anatomical Positions
The body is upright, facing forward, and standing erect.
The feet are parallel and flat on the floor.
The arms are hanging by the...
Glaucoma: Overview
Open Angle Glaucoma: Treatment
Drugs such as carbonic anhydrase inhibitors, α2- and...
Angle Closure Glaucoma: Treatment
Parenteral Anesthetics: Overview
Increased Intracranial Pressure l: Introduction

