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Proceedings of CAD'15, 2015, 216-221
Measuring Mean Cup Depth in the Optic Nerve Head

John K. Johnstone, Lindsay Rhodes, Massimo Fazio, Brandon Smith, Lan Wang,
J. Crawford Downs, Cynthia Owsley, Christopher A. Girkin, University of Alabama at Birmingham

Abstract. Structural changes in the optic nerve head (ONH) have been associated with the development of glaucomatous optic neuropathy, in particular, expansion of the optic cup due to loss of neuroretinal tissues and remodeling of the underlying lamina cribrosa, motivating a quantitative analysis of ONH morphology. Cup depth is a useful measure that reflects the anatomical changes seen in glaucoma and can be calculated based on the shape of the internal limiting membrane (ILM).  This paper considers the computation of mean cup depth. Unlike previous studies that have computed cup depth directly from images, from few samples, or that assess cup depth qualitatively rather than quantitatively, we build a full shape model of the ILM from dense point clouds.  We also use algorithms from shape modeling to build reference structures and to measure cup depth, as opposed to using manual measurements. To measure depth, a reference structure is necessary.  A reference plane based on Bruch's membrane (BM) has been used in both clinical and histological studies against which to measure depth in the ONH. The opening of Bruch's membrane (BMO), the inner boundary of Bruch's membrane at the anterior end of the neural canal, is nearly planar and nearly elliptical, making it a good candidate for a reference structure. 

Keywords. Cup Depth, Modeling of the Internal Limiting Membrane, Bruch Reference Structure, Uniform Sampling

DOI: 10.14733/cadconfP.2015.216-221