Abstract
Purpose :
To extract the deformation field at the optic cup using coherent point drift non-rigid registration on the 3D internal limiting membrane (ILM) surface extracted from the optical coherence tomography (OCT) volumes.
Methods :
Optic nerve head (ONH) OCT volumes (Cirrus HD-OCT, 200x200 ONH cube, Zeiss, Dublin, CA) were acquired on both eyes of healthy and glaucoma subjects (10 subjects for each group). For each subject, another scan was acquired a year later (> 365 days and < 395 days). First, speckle noise was removed from the volumes using a previously published deep learning-based image enhancement method. The 3D ILM surface was then extracted automatically using another deep learning-based segmentation in both volumes as 3D point sets and rigidly registered using signature of histograms of orientations (SHOT) feature descriptor matching and iterative closest point (ICP) in order to bring the images into the same reference frame. The peripheral regions of the registered surfaces were excluded from the subsequent non-rigid registration step. Coherent point drift (CPD) was then used to quantify the deformation at the optic cup on the 3D ILM surface point set. The maximum and average absolute deformation amount in the superior, inferior, temporal and nasal quadrants were measured for each subject, and statistically compared between the three cohorts.
Results :
The registration results were illustrated as deformation vectors with colour graduation in Fig. 1. The POAG subjects showed statistically significantly higher mean absolute deformation than healthy subjects 0.027mm (standard deviation=0.020mm) vs. 0.013mm (SD=0.0050mm) (p < 0.001). The maximum deformation in the superior quadrant was also found to be significantly (p < 0.001) larger in the POAG patients than the healthy subjects.
Conclusions :
The reported novel OCT registration system successfully quantified the deformations at the optic cup in longitudinal OCT volumes. This allows us to monitor and track localized changes in optic cup that may lead to uncovering the association between the spatial optic cup deformation pattern and visual field deterioration.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.