title: Repeatability of corneal phase retardation measurements by polarization-sensitive optical coherence tomography.
abstract: OBJECTIVE
  Polarization-sensitive optical coherence tomography (PS-OCT) can evaluate internal tissue structures of the cornea, such as collagen fibers, by phase retardation measurement. In this study, we assessed the repeatability of corneal phase retardation measurements using anterior segment PS-OCT.
  
  
  METHODS
  A total of 173 eyes of 173 patients were measured using PS-OCT. In total, 58 eyes of young subjects with normal corneas, 28 eyes of old subjects with normal corneas, 26 eyes with corneal dystrophy or degeneration, 37 eyes with corneal transplantation, and 24 eyes with keratoconus were evaluated. The 3-mm diameter average of en face phase retardation of the posterior corneal surface was examined using PS-OCT. To evaluate the repeatability, intraclass correlation coefficients (ICCs) were calculated for intraobserver repeatability and interobserver repeatability analysis.
  
  
  RESULTS
  Polarization-sensitive OCT showed good repeatability for corneal measurements. Intraclass correlation coefficients of intraobserver and interobserver repeatability of all the subjects were 0.989 and 0.980, respectively. Intraclass correlation coefficients of the intraobserver for each group, that is, young and old subjects with normal cornea, cornea dystrophy/degeneration, corneal transplantation, and keratoconus, were 0.961, 0.975, 0.984, 0.978, and 0.996, respectively. Interobserver ICCs for the above-mentioned respective groups were 0.952, 0.964, 0.988, 0.959, and 0.975, respectively.
  
  
  CONCLUSIONS
  Polarization-sensitive OCT showed good repeatability for phase retardation measurements of central corneas not only for normal corneas, but also for various diseased corneas. Polarization-sensitive OCT might be useful for evaluating corneal phase retardation, which is one of the parameters that defines birefringence.
authors.affiliation: Department of Ophthalmology, Institute of Clinical Medicine, University of Tsukuba, Ibaraki, Japan 2Computational Optics and Ophthalmology Group, Ibaraki, Japan.
authors.forename: Shinichi
authors.initials: S
authors.lastname: Fukuda
authors.affiliation: Department of Ophthalmology, Institute of Clinical Medicine, University of Tsukuba, Ibaraki, Japan.
authors.forename: Genichiro
authors.initials: G
authors.lastname: Kishino
authors.affiliation: Department of Ophthalmology, Institute of Clinical Medicine, University of Tsukuba, Ibaraki, Japan.
authors.forename: Sujin
authors.initials: S
authors.lastname: Hoshi
authors.affiliation: Department of Ophthalmology, Institute of Clinical Medicine, University of Tsukuba, Ibaraki, Japan.
authors.forename: Simone
authors.initials: S
authors.lastname: Beheregaray
authors.affiliation: Department of Ophthalmology, Institute of Clinical Medicine, University of Tsukuba, Ibaraki, Japan.
authors.forename: Yuta
authors.initials: Y
authors.lastname: Ueno
authors.affiliation: Department of Molecular Therapy, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Tokyo, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Fukuda
authors.affiliation: Computational Optics and Ophthalmology Group, Ibaraki, Japan 4Computational Optics Group, University of Tsukuba, Ibaraki, Japan.
authors.forename: Deepa
authors.initials: D
authors.lastname: Kasaragod
authors.affiliation: Computational Optics and Ophthalmology Group, Ibaraki, Japan 4Computational Optics Group, University of Tsukuba, Ibaraki, Japan.
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Yasuno
authors.affiliation: Department of Ophthalmology, Institute of Clinical Medicine, University of Tsukuba, Ibaraki, Japan 2Computational Optics and Ophthalmology Group, Ibaraki, Japan.
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Oshika
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001718:Birefringence; D003315:Cornea / Q000033:anatomy & histology; D003316:Corneal Diseases / Q000175:diagnosis*; D005260:Female; D006801:Humans; D007640:Keratoconus / Q000175:diagnosis; D015948:Keratoplasty, Penetrating; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D015203:Reproducibility of Results; D041623:Tomography, Optical Coherence / Q000379:methods*; D055815:Young Adult