title: Measuring retinal nerve fiber layer birefringence, retardation, and thickness using wide-field, high-speed polarization sensitive spectral domain OCT.
abstract: OBJECTIVE
  We  presented a novel polarization sensitive optical coherence tomography (PS-OCT) system for measuring retinal nerve fiber layer (RNFL) birefringence, retardation, and thickness, and report on the repeatability of acquiring these quantities.
  
  
  METHODS
  A new PS-OCT system, measuring at 840 nm, was developed that supports scan angles of up to 40° × 40° with an A-scan rate of 70 kHz. To test the performance and reproducibility, we measured 10 eyes of 5 healthy human volunteers five times each. All volunteers were imaged further with scanning laser polarimetry (SLP). The obtained RNFL birefringence, retardation, and thickness maps were averaged, and standard deviation maps were calculated. For quantitative comparison between the new PS-OCT and SLP, a circumpapillary evaluation within 2 annular segments (superior and inferior to the optic disc) was performed.
  
  
  RESULTS
  High quality RNFL birefringence, retardation, and thickness maps were obtained. Within the superior and inferior segments, the mean retardation for individual eyes ranged from 20° to 28.9° and 17.2° to 28.2°, respectively. The quadrant precision over the 5 consecutive measurements for each subject, calculated for the average retardation obtained within the superior and inferior quadrants ranged from 0.16° to 0.69°. The mean birefringence ranged from 0.106°/μm to 0.141°/μm superior and 0.101°/μm to 0.135°/μm inferior, with a quadrant precision of 0.001°/μm to 0.007°/μm. The mean RNFL thickness varied from 114 to 150 μm superior, and 111 to 140.9 μm inferior (quadrant precision ranged from 3.6 to 11.9 μm).
  
  
  CONCLUSIONS
  The new PS-OCT system showed high image quality and reproducibility, and, therefore, might be a valuable tool for glaucoma diagnosis.
authors.affiliation: Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria. stefan.zotter@meduniwien.ac.at
authors.forename: Stefan
authors.initials: S
authors.lastname: Zotter
authors.forename: Michael
authors.initials: M
authors.lastname: Pircher
authors.forename: Erich
authors.initials: E
authors.lastname: Götzinger
authors.forename: Teresa
authors.initials: T
authors.lastname: Torzicky
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Yoshida
authors.forename: Futoshi
authors.initials: F
authors.lastname: Hirose
authors.forename: Stephan
authors.initials: S
authors.lastname: Holzer
authors.forename: Julia
authors.initials: J
authors.lastname: Kroisamer
authors.forename: Clemens
authors.initials: C
authors.lastname: Vass
authors.forename: Ursula
authors.initials: U
authors.lastname: Schmidt-Erfurth
authors.forename: Christoph K
authors.initials: CK
authors.lastname: Hitzenberger
mesh_terms: D000328:Adult; D001718:Birefringence; D005260:Female; D005901:Glaucoma / Q000473:pathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009412:Nerve Fibers; D012016:Reference Values; D015203:Reproducibility of Results; D012160:Retina / Q000166:cytology*; D057109:Scanning Laser Polarimetry / Q000295:instrumentation / Q000379:methods / Q000592:standards*; D041623:Tomography, Optical Coherence / Q000295:instrumentation / Q000379:methods / Q000592:standards*