title: Complex wavelet based quality assessment for AS-OCT images with application to Angle Closure Glaucoma diagnosis.
abstract: OBJECTIVE
  Angle closure disease in the eye can be detected using time-domain Anterior Segment Optical Coherence Tomography (AS-OCT). The Anterior Chamber (AC) characteristics can be quantified from AS-OCT image, which is dependent on the image quality at the image acquisition stage. To date, to the best of our knowledge there are no objective or automated subjective measurements to assess the quality of AS-OCT images.
  
  
  METHODS
  To address AS-OCT image quality assessment issue, we define a method for objective assessment of AS-OCT images using complex wavelet based local binary pattern features. These features are pooled using the Naïve Bayes classifier to obtain the final quality parameter. To evaluate the proposed method, a subjective assessment has been performed by clinical AS-OCT experts, who graded the quality of AS-OCT images on a scale of good, fair, and poor. This was done based on the ability to identify the AC structures including the position of the scleral spur.
  
  
  RESULTS
  We compared the results of the proposed objective assessment with the subjective assessments. From this comparison, it is validated that the proposed objective assessment has the ability of differentiating the good and fair quality AS-OCT images for glaucoma diagnosis from the poor quality AS-OCT images.
  
  
  CONCLUSIONS
  This proposed algorithm is an automated approach to evaluate the AS-OCT images with the intention for collecting of high quality data for further medical diagnosis. Our proposed quality index has the ability of automatic objective and quantitative assessment of AS-OCT image quality and this quality index is similar to glaucoma specialist.
authors.affiliation: School of Computer Engineering, Nanyang Technological University (NTU), 639798 Singapore. Electronic address: issacniwas@ntu.edu.sg.
authors.forename: Swamidoss Issac
authors.initials: SI
authors.lastname: Niwas
authors.affiliation: School of Computer Engineering, Nanyang Technological University (NTU), 639798 Singapore; Department of Electronics and Computer Engineering, Hong Kong University of Science and Technology (HKUST), Hong Kong. Electronic address: vjakhetiya@connect.ust.hk.
authors.forename: Vinit
authors.initials: V
authors.lastname: Jakhetiya
authors.affiliation: School of Computer Engineering, Nanyang Technological University (NTU), 639798 Singapore. Electronic address: wslin@ntu.edu.sg.
authors.forename: Weisi
authors.initials: W
authors.lastname: Lin
authors.affiliation: School of Computer Engineering, Nanyang Technological University (NTU), 639798 Singapore. Electronic address: asckkwoh@ntu.edu.sg.
authors.forename: Chee Keong
authors.initials: CK
authors.lastname: Kwoh
authors.affiliation: Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore (NUS), 119228 Singapore. Electronic address: chelvin@gmail.com.
authors.forename: Chelvin C
authors.initials: CC
authors.lastname: Sng
authors.affiliation: Eye Surgery Centre, National University Health System (NUHS), 119228 Singapore. Electronic address: mcdaquino@gmail.com.
authors.forename: Maria Cecilia
authors.initials: MC
authors.lastname: Aquino
authors.affiliation: Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore (NUS), 119228 Singapore. Electronic address: viktorkoh@gmail.com.
authors.forename: Koh
authors.initials: K
authors.lastname: Victor
authors.affiliation: Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore (NUS), 119228 Singapore. Electronic address: ophchewp@nus.edu.sg.
authors.forename: Paul T K
authors.initials: PT
authors.lastname: Chew
mesh_terms: D015812:Glaucoma, Angle-Closure / Q000503:physiopathology*; D006801:Humans; D041623:Tomography, Optical Coherence
keywords: Angle closure glaucoma; Complex wavelets; Image quality assessment; Local binary pattern; Machine learning; Optical coherence tomography