title: Anatomic vs. acquired image frame discordance in spectral domain optical coherence tomography minimum rim measurements.
abstract: OBJECTIVE
  To quantify the effects of using the fovea to Bruch's membrane opening (FoBMO) axis as the nasal-temporal midline for 30° sectoral (clock-hour) spectral domain optical coherence tomography (SDOCT) optic nerve head (ONH) minimum rim width (MRW) and area (MRA) calculations.
  
  
  METHODS
  The internal limiting membrane and BMO were delineated within 24 radial ONH B-scans in 222 eyes of 222 participants with ocular hypertension and glaucoma. For each eye the fovea was marked within the infrared reflectance image, the FoBMO angle (θ) relative to the acquired image frame (AIF) horizontal was calculated, the ONH was divided into 30° sectors using a FoBMO or AIF nasal/temporal axis, and SDOCT MRW and MRA were quantified within each FoBMO vs. AIF sector. For each sector, focal rim loss was calculated as the MRW and MRA gradients (i.e. the difference between the value for that sector and the one clockwise to it divided by 30°). Sectoral FoBMO vs. AIF discordance was calculated as the difference between the FoBMO and AIF values for each sector. Generalized estimating equations were used to predict the eyes and sectors of maximum FoBMO vs. AIF discordance.
  
  
  RESULTS
  The mean FoBMO angle was -6.6±4.2° (range: -17° to +7°). FoBMO vs. AIF discordance in sectoral mean MRW and MRA was significant for 7 of 12 and 6 of 12 sectors, respectively (p<0.05, Wilcoxon test, Bonferroni correction). Eye-specific, FoBMO vs. AIF sectoral discordance was predicted by sectoral rim gradient (p<0.001) and FoBMO angle (p<0.001) and achieved maximum values of 83% for MRW and 101% for MRA.
  
  
  CONCLUSIONS
  Using the FoBMO axis as the nasal-temporal axis to regionalize the ONH rather than a line parallel to the AIF horizontal axis significantly influences clock-hour SDOCT rim values. This effect is greatest in eyes with large FoBMO angles and sectors with focal rim loss.
authors.affiliation: Optic Nerve Head Research Laboratory, Legacy Health, Portland, Oregon, United States of America.
authors.forename: Lin
authors.initials: L
authors.lastname: He
authors.affiliation: Optic Nerve Head Research Laboratory, Legacy Health, Portland, Oregon, United States of America.
authors.forename: Ruojin
authors.initials: R
authors.lastname: Ren
authors.affiliation: Optic Nerve Head Research Laboratory, Legacy Health, Portland, Oregon, United States of America; Discoveries in Sight Research Laboratories of the Devers Eye Institute, Legacy Health, Portland, Oregon, United States of America.
authors.forename: Hongli
authors.initials: H
authors.lastname: Yang
authors.affiliation: Optic Nerve Head Research Laboratory, Legacy Health, Portland, Oregon, United States of America.
authors.forename: Christy
authors.initials: C
authors.lastname: Hardin
authors.affiliation: Optic Nerve Head Research Laboratory, Legacy Health, Portland, Oregon, United States of America.
authors.forename: Luke
authors.initials: L
authors.lastname: Reyes
authors.affiliation: Optic Nerve Head Research Laboratory, Legacy Health, Portland, Oregon, United States of America; Discoveries in Sight Research Laboratories of the Devers Eye Institute, Legacy Health, Portland, Oregon, United States of America.
authors.forename: Juan
authors.initials: J
authors.lastname: Reynaud
authors.affiliation: Discoveries in Sight Research Laboratories of the Devers Eye Institute, Legacy Health, Portland, Oregon, United States of America.
authors.forename: Stuart K
authors.initials: SK
authors.lastname: Gardiner
authors.affiliation: Discoveries in Sight Research Laboratories of the Devers Eye Institute, Legacy Health, Portland, Oregon, United States of America.
authors.forename: Brad
authors.initials: B
authors.lastname: Fortune
authors.affiliation: Discoveries in Sight Research Laboratories of the Devers Eye Institute, Legacy Health, Portland, Oregon, United States of America.
authors.forename: Shaban
authors.initials: S
authors.lastname: Demirel
authors.affiliation: Optic Nerve Head Research Laboratory, Legacy Health, Portland, Oregon, United States of America; Discoveries in Sight Research Laboratories of the Devers Eye Institute, Legacy Health, Portland, Oregon, United States of America.
authors.forename: Claude F
authors.initials: CF
authors.lastname: Burgoyne
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D005584:Fovea Centralis / Q000473:pathology; D005901:Glaucoma / Q000175:diagnosis / Q000473:pathology*; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009898:Optic Disk / Q000473:pathology; D009929:Organ Size; D041623:Tomography, Optical Coherence