title: Automated segmentation of neural canal opening and optic cup in 3D spectral optical coherence tomography volumes of the optic nerve head.
abstract: OBJECTIVE
  To develop an automated approach for segmenting the neural canal opening (NCO) and cup at the level of the retinal pigment epithelium (RPE)/Bruch's membrane (BM) complex in spectral-domain optical coherence tomography (SD-OCT) volumes. To investigate the correspondence and discrepancy between the NCO-based metrics and the clinical disc margin on fundus photographs of glaucoma subjects.
  
  
  METHODS
  SD-OCT scans and corresponding stereo fundus photographs of the optic nerve head were obtained from 68 eyes of 34 patients with glaucoma or glaucoma suspicion. Manual planimetry was performed by three glaucoma experts to delineate a reference standard (RS) for cup and disc margins from the images. An automated graph-theoretic approach was used to identify the NCO and cup. NCO-based metrics were compared with the RS.
  
  
  RESULTS
  Compared with the RS disc margin, the authors found mean unsigned and signed border differences of 2.81 ± 1.48 pixels (0.084 ± 0.044 mm) and -0.99 ± 2.02 pixels (-0.030 ± 0.061 mm), respectively, for NCO segmentation. The correlations of the linear cup-to-disc (NCO) area ratio, disc (NCO) area, rim area, and cup area of the algorithm with the RS were 0.85, 0.77, 0.69, and 0.83, respectively.
  
  
  CONCLUSIONS
  In most eyes, the NCO-based 2D metrics, as estimated by the novel automated graph-theoretic approach to segment the NCO and cup at the level of the RPE/BM complex in SD-OCT volumes, correlate well with RS. However, a small discrepancy exists in NCO-based anatomic structures and the clinical disc margin of the RS in some eyes.
authors.affiliation: Department of Electrical and Computer Engineering, University of Iowa, Iowa City, Iowa 52242, USA. zhihong-hu@uiowa.edu
authors.forename: Zhihong
authors.initials: Z
authors.lastname: Hu
authors.forename: Michael D
authors.initials: MD
authors.lastname: Abràmoff
authors.forename: Young H
authors.initials: YH
authors.lastname: Kwon
authors.forename: Kyungmoo
authors.initials: K
authors.lastname: Lee
authors.forename: Mona K
authors.initials: MK
authors.lastname: Garvin
mesh_terms: D000465:Algorithms; D016570:Bruch Membrane / Q000473:pathology; D015812:Glaucoma, Angle-Closure / Q000175:diagnosis*; D005902:Glaucoma, Open-Angle / Q000175:diagnosis*; D006801:Humans; D021621:Imaging, Three-Dimensional; D054259:Neural Tube / Q000473:pathology*; D015588:Observer Variation; D009798:Ocular Hypertension / Q000175:diagnosis; D009898:Optic Disk / Q000473:pathology*; D055213:Retinal Pigment Epithelium / Q000473:pathology; D041623:Tomography, Optical Coherence