title: The Effect of Optic Disc Center Displacement on Retinal Nerve Fiber Layer Measurement Determined by Spectral Domain Optical Coherence Tomography.
abstract: OBJECTIVE
  To investigate the effect of optic disc center displacement on retinal nerve fiber layer (RNFL) measurement determined by spectral domain optical coherence tomography (SD-OCT).
  
  
  METHODS
  The optic disc center was manipulated at 1-pixel intervals in horizontal, vertical, and diagonal directions. According to the manipulated optic disc center location, the RNFL thickness data were resampled: (1) at a 3.46-mm diameter circle; and (2) between a 2.5-mm diameter circle and 5.4-mm square. Error was calculated between the original and resampled RNFL measurements. The tolerable error threshold of the optic disc center displacement was determined by considering test-retest variability of SD-OCT. The unreliable zone was defined as an area with 10% or more variability.
  
  
  RESULTS
  The maximum tolerable error thresholds of optic disc center displacement on the RNFL thickness map were distributed from 0.042 to 0.09 mm in 8 directions. The threshold shape was vertically elongated. Clinically important unreliable zones were located: (1) at superior and inferior region in the vertical displacement; (2) at inferotemporal region in the horizontal displacement, and (3) at superotemporal or inferotemporal region in the diagonal displacement. The unreliable zone pattern and threshold limit varied according to the direction of optic disc displacement.
  
  
  CONCLUSIONS
  Optic disc center displacement had a considerable impact on whole RNFL thickness measurements. Understanding the effect of optic disc center displacement could contribute to reliable RNFL measurements.
authors: Department of Ophthalmology, College of Medicine, Hanyang University, Seoul, Korea.|Department of Ophthalmology, Asan Medical Center, College of Medicine, University of Ulsan, Seoul, Korea.
authors: Joong Won
authors: JW
authors: Shin
authors: Department of Ophthalmology, College of Medicine, Hanyang University, Seoul, Korea.|Department of Ophthalmology, Hanyang University Guri Hospital, College of Medicine, Hanyang University, Guri, Korea.
authors: Yong Un
authors: YU
authors: Shin
authors: Department of Ophthalmology, College of Medicine, Hanyang University, Seoul, Korea.
authors: Ki Bang
authors: KB
authors: Uhm
authors: Department of Ophthalmology, Asan Medical Center, College of Medicine, University of Ulsan, Seoul, Korea.
authors: Kyung Rim
authors: KR
authors: Sung
authors: Department of Ophthalmology, College of Medicine, Hanyang University, Seoul, Korea.|Department of Ophthalmology, Hanyang University Guri Hospital, College of Medicine, Hanyang University, Guri, Korea.
authors: Min Ho
authors: MH
authors: Kang
authors: Department of Ophthalmology, College of Medicine, Hanyang University, Seoul, Korea.|Department of Ophthalmology, Hanyang University Guri Hospital, College of Medicine, Hanyang University, Guri, Korea.
authors: Hee Yoon
authors: HY
authors: Cho
authors: Department of Ophthalmology, College of Medicine, Hanyang University, Seoul, Korea.|Department of Ophthalmology, Hanyang University Guri Hospital, College of Medicine, Hanyang University, Guri, Korea.
authors: Mincheol
authors: M
authors: Seong
mesh_terms: D000328:Adult; D003430:Cross-Sectional Studies; D005260:Female; D005901:Glaucoma / Q000175:diagnosis / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009412:Nerve Fibers / Q000502:physiology*; D009898:Optic Disk / Q000000981:diagnostic imaging*; D011446:Prospective Studies; D012160:Retina / Q000000981:diagnostic imaging*; D041623:Tomography, Optical Coherence; D058609:Visual Field Tests