AUTHOR=Malhotra Kiran , Patel Megh D. , Shirazi Zainab , Moss Heather E. 

TITLE=Association Between Peripapillary Bruch's Membrane Shape and Intracranial Pressure: Effect of Image Acquisition Pattern and Image Analysis Method, a Preliminary Study

JOURNAL=Frontiers in Neurology

VOLUME=Volume 9 - 2018

YEAR=2018

URL=https://www.frontiersin.org/journals/neurology/articles/10.3389/fneur.2018.01137

DOI=10.3389/fneur.2018.01137

ISSN=1664-2295

ABSTRACT=Background/Aims: High intracranial pressure (ICP) is associated with changes in peripapillary Bruch's membrane shape on optical coherence tomography (OCT) images of the optic nerve head. It is not known if image acquisition pattern and analysis method impact this association.

Materials and Methods: Cross sectional OCT scans of the optic nerve head were obtained at six angles using a radial scan pattern in 21 subjects immediately prior to ICP measurement via lumbar puncture. On each image, Bruch's membrane was manually segmented and defined by either 14 or 16 semi-landmarks and either rater identified, or distance identified boundaries. For each of these four image analysis strategies, geometric morphometric analysis identified the first principal component of Bruch's membrane shape for all images and for the set of images taken at each angle.  Repeated measures ANOVA of the first principal component magnitude for all images assessed for shape difference between image angles. Linear generalized estimating equation models assessed association between angle specific first principal components and ICP for each angle. Receiver operating characteristic analysis assessed angle specific first principal components’ ability to differentiate elevated from normal ICP. 

Results: The first principal component represented defection into the vitreous for all scan angles, but quantitatively differed across scan angles (p<0.005, repeated measures ANOVA). Angle specific first principal components were positively correlated with ICP (p<0.005 for all angles, generalized estimating equation models). All angle specific first principal components showed excellent ability to classify ICP (area under curve  0.8 for all).  These results were independent from image analysis strategy. 

Discussion: Qualitative changes in Bruch's membrane shape are similar regardless of 2-D scan angle. They differ quantitatively between  scan angles, and therefore PC1 extracted from different scan angles can’t be compared between individuals.  There is a similarly strong linear relationship between the PC1 and ICP for each scan angle. Angle specific PC1 showed similarly excellent ability to differentiate elevated from normal ICP.  The results support development of Bruch's membrane shape extracted from 2-D optic nerve head OCT scans as a biomarker of ICP and emphasize the importance of consistency of scan angle.