In vivo optic nerve head mechanical response to intraocular and cerebrospinal fluid pressure: imaging protocol and quantification method

Massimo A Fazio,Luigi Bruno,Mark E Clark,Christopher A Girkin

doi:10.1038/s41598-018-31052-x

Massimo A Fazio, Luigi Bruno + Show 2 more

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https://doi.org/10.1038/s41598-018-31052-x

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Abstract

This study presents a quantification method for the assessment of the optic nerve head (ONH) deformations of the living human eye under acute intraocular pressure (IOP) elevation and change of cerebrospinal fluid pressure (CSFP) with body position. One eye from a brain-dead organ donor with open-angle glaucoma was imaged by optical coherence tomography angiography during an acute IOP and CSFP elevation test. Volumetric 3D strain was computed by digital volume correlation. With increase in IOP the shear strain consistently increased in both sitting and supine position (p < 0.001). When CSFP was increased at constant IOP by changing body position, a global reduction in the ONH strain was observed (−0.14% p = 0.0264). Strain in the vasculature was significantly higher than in the structural tissue (+0.90%, p = 0.0002). Retinal nerve fiber layer (RNFL) thickness strongly associated (ρ = −0.847, p = 0.008) with strain in the peripapillary sclera (ppScl) but not in the retina (p = 0.433) and lamina (p = 0.611). These initial results show that: CSFP independently to IOP modulates strain in the human ONH; ppScl strains are greater than strains in lamina and retina; strain in the retinal vasculature was higher than in the structural tissue; In this glaucoma eye, higher ppScl strain associated with lower RNFL thickness.

Highlights

Computational studies suggest that unlike the oppositional forces from cerebrospinal fluid pressure (CSFP), there are 2 components of IOP-induced deformation of the optic nerve head (ONH): (1) posterior displacement of the lamina cribrosa (LC) by the direct effect of IOP, which is counterbalanced by (2) IOP-induced scleral canal expansion, which pulls[4] the LC anterior within the canal
The purpose of this study is to present the imaging protocol and quantification methods to differentially estimate in vivo ONH deformations in response changes in IOP and CSFP within the LC, retina and peripapillary sclera (ppScl) using digital volume correlation (DVC) in the cannulated living eye
We developed an imaging and quantification method to resolve ONH mechanical response to changes in IOP and CSFP in the living human eye of a brain-dead organ donor

Summary

Introduction

Computational studies suggest that unlike the oppositional forces from CSFP, there are 2 components of IOP-induced deformation of the ONH: (1) posterior displacement of the LC by the direct effect of IOP, which is counterbalanced by (2) IOP-induced scleral canal expansion, which pulls[4] the LC anterior within the canal. The methods presented in this study allow for the control of IOP while changing body position which affords the ability to estimate and alter CSFP using the extinction point for spontaneous venous pulsation in a living human eye. The purpose of this study is to present the imaging protocol and quantification methods to differentially estimate in vivo ONH deformations in response changes in IOP and CSFP within the LC, retina and ppScl using digital volume correlation (DVC) in the cannulated living eye

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