Abstract
We have developed a novel optical approach to determine pulsatile ocular volume changes using automated segmentation of the choroid, which, together with Dynamic Contour Tonometry (DCT) measurements of intraocular pressure (IOP), allows estimation of the ocular rigidity (OR) coefficient. Spectral Domain Optical Coherence Tomography (OCT) videos were acquired with Enhanced Depth Imaging (EDI) at 7Hz during ~50 seconds at the fundus. A novel segmentation algorithm based on graph search with an edge-probability weighting scheme was developed to measure choroidal thickness (CT) at each frame. Global ocular volume fluctuations were derived from frame-to-frame CT variations using an approximate eye model. Immediately after imaging, IOP and ocular pulse amplitude (OPA) were measured using DCT. OR was calculated from these peak pressure and volume changes. Our automated segmentation algorithm provides the first non-invasive method for determining ocular volume change due to pulsatile choroidal filling, and the estimation of the OR constant. Future applications of this method offer an important avenue to understanding the biomechanical basis of ocular pathophysiology.
Highlights
The development of non-invasive methods to estimate ocular rigidity (OR) will have profound implications for research into ocular disease
This work introduces a novel method for assessing the Ocular Rigidity non-invasively from Optical Coherence Tomography (OCT) time series and usual biometric measurements
In the subsections we describe experiments that demonstrate the improvements provided by this novel choroidal-scleral interface (CSI) segmentation, as well as OR measurements on our cohort of subjects that validate the methodology
Summary
The development of non-invasive methods to estimate ocular rigidity (OR) will have profound implications for research into ocular disease. Considerable recent evidence from experimental studies in primates and from mathematical modeling suggests that ocular biomechanics may play a major role in glaucoma pathogenesis [8,9,10,11,12,13,14,15,16,17]. According to finite element modeling, major determinants of optic nerve head stress and strain leading to glaucoma damage include IOP, and scleral elasticity as well as other biomechanical factors. Scleral elasticity is considered to be the most important determinant of optic nerve head stress and strain, more important than IOP [18] and it is clear that additional factors, such as ocular biomechanics, must play an important role
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