Noninvasive intracranial pressure assessment using otoacoustic emissions: An application in glaucoma.

Allison R Loiselle,Pim Van Dijk,Nomdo M Jansonius,Emile De Kleine,Sanjoy Bhattacharya

doi:10.1371/journal.pone.0204939

Abstract

The theory that glaucoma patients have a lower intracranial pressure (ICP) than healthy subjects is a controversial one. The aim of this study was to assess ICP noninvasively by determining the relationship between distortion product otoacoustic emission (DPOAE) phase and body position and to compare this relationship between patients with primary open angle glaucoma (POAG), patients with normal tension glaucoma (NTG), and controls. The relationship was also calibrated using published data regarding invasive measurements of ICP versus body position. DPOAEs were measured in 30 controls and 32 glaucoma patients (17 POAG, 15 NTG) at the following body positions (assuming 90° as upright): 45, 30, 20, 10, 0 (supine), -10, and -20°. DPOAE phase had a clear, nonlinear relationship with body position. The mean DPOAE phase shifts between the two most extreme body positions (45 to -20°) were 73.6, 80.7, and 66.3° for healthy, POAG, and NTG, respectively (P = 0.73), and the groups showed the same, nonlinear behaviour. This indicates that there is no evidence that glaucoma patients have a reduced ICP. When calibrated with invasive data, ICP and DPOAE phase were linearly related over an ICP of 3 mmHg. This suggests that, more broadly, DPOAEs could be used in the future to monitor changes in ICP in a clinical setting and to measure dynamic changes in ICP such as diurnal fluctuations or changes induced by certain medications.

Highlights

Primary open angle glaucoma (POAG) is a chronic and progressive eye disease characterized by loss of retinal ganglion cells, thinning of the retinal nerve fiber layer, and subsequent visual field loss
The within test variability was low and fairly stable across all body positions, with a standard deviation (SD) of differences ranging from 5.3 ̊ to 10.2 ̊
There is a nonlinear relationship between distortion product otoacoustic emission (DPOAE) phase and body position that is similar in healthy subjects and patients with primary open angle glaucoma (POAG) and normal tension glaucoma (NTG)

Summary

Introduction

Primary open angle glaucoma (POAG) is a chronic and progressive eye disease characterized by loss of retinal ganglion cells, thinning of the retinal nerve fiber layer, and subsequent visual field loss. An elevated intraocular pressure (IOP) was deemed to be the key factor in the pathophysiology of glaucoma. There is a variant of POAG in which the patients have a normal IOP Noninvasive ICP measurement in glaucoma analysis, decision to publish, or preparation of the manuscript

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