Adjustment of optic disc center displacement using Cirrus HD-OCT Research Browser.

<p>(A) The optic disc margin detection error (arrowheads) was highly suspect compared with the red-free photograph, and led to miscalculation of the optic disc center [0.09, 0 mm]. (B) Cirrus HD-OCT Research Browser provides an editing tool for adjusting the optic disc center and margin. After the optic disc center was adjusted to [0.18, -0.09 mm] by semi-automatic manipulation using the editing tool, the original shape of the optic disc margin was restored (arrowheads). Comparing two coordinates of the optic disc centers, superotemporal [-0.09, 0.09 mm] displacement (red asterisk) was observed. This corresponds to the boundary of the cautious threshold limit and should be interpreted with caution. (C) We can estimate or confirm the effect of optic disc center displacement using the displacement error-encoded map. In superotemporal displacement, the major clinical concern is the inferotemporal unreliable zone in which the greatest decrease is expected. Indeed, the red-coded area and its angular width increased 2.45 to 2.69 mm² (9.8%) and 23.7 to 26.5° (11.8%). Minor changes in the superotemporal (increased yellow-coded area) and inferonasal region (decreased yellow- and red-coded area) were also consistent with the displacement error-encoded map. OCT = optical coherence tomography</p

Interpretation of optic disc center displacement in Guided Progression Analysis (GPA).

<p>(A) At second baseline exam in GPA, the optic disc margin (yellow arrowhead) showed eccentric shape compared with other exams (black arrowheads). As a result, following RNFL thickness change maps showed RNFL progression at unusual region (inferonasal rectangles) and superotemporal region (asterisk). (B) Manual delineation (blue irregular arc) indicated that the direction of optic disc center displacement was estimated to be temporal (thin black arrows). (C) In temporal displacement, overestimated inferonasal region (rectangle) at baseline study might lead to false RNFL progression in GPA. In contrast, underestimated inferotemproal region (thick gray arrows) at baseline showed increasing RNFL thickness in follow-up exams (thick black arrows). Mild superotemporal underestimation (asterisk) at baseline might underestimate actual RNFL progression. (D) Using manual selection mode in GPA, we removed second exam from analysis. Abnormal RFNL progression at inferonasal region was proven to be the effect of optic disc center displacement. Superotemporal RNFL progression became larger and more obvious. RNFL = retinal nerve fiber layer</p

Interpretation of optic disc center displacement in case of floater.

<p>(A) Floater (arrowheads) interfered with the optic disc margin detection (black irregular circle) in the inferior region. Manual delineation (blue irregular arc) indicated that the direction of optic disc center displacement was estimated to be inferonasal (arrows). (B) At next follow-up exam (6 month interval), the floater (arrowhead) moved nasal side, and then optic disc margin was clearly detected. Although inferotemporal and superotemporal RNFL defects seemed to be progressed in the RNFL deviation map, there had been no evidence of such rapid progression in other structural and functional tests. Optic disc center displacement might affect the change of red and yellow-coded area. (C) In inferonasal displacement, there was greater chance of overestimation of RNFL thickness in inferotemporal region. Superotemporal region also was suspicious of mild overestimation. These were consistent with relatively small RNFL defects in first exam. RNFL = retinal nerve fiber layer</p

Optic disc center displacement and circumpapillary RNFL thickness error.

<p>Average RNFL thickness showed the smallest error for optic disc center displacement in 8 directions. The red marks on graphs represent the first significantly different optic disc center displacement between the original and resampled RNFL measurements on repeated measures ANOVA. The central green and yellow zone represents the maximum tolerable (5% or less variability) and cautious (10% or less variability) thresholds of optic disc center displacement. RNFL = retinal nerve fiber layer; ANOVA = analysis of variance</p

Clinically important unreliable zone in terms of susceptible area for glaucomatous damage.

<p>Clinically important unreliable zone in terms of susceptible area for glaucomatous damage.</p

Optic disc center displacement and measurement error in the RNFL thickness map.

<p>Each displacement error-encoded map recorded differences between the original and resampled RNFL measurements at the maximum cautious threshold level (left upper corner). The black lines on the displacement error-encoded maps are the unreliable zones in which 10% or more variability was observed. The central green and yellow zone represents the maximum tolerable (5% or less variability occupying more than 80% of map) and cautious (10% or less variability occupying more than 80% of map) thresholds of optic disc center displacement. RNFL = retinal nerve fiber layer</p

Optic disc center displacement between optic disc photography and optical coherence tomography (OCT).

<p>The infrared image of deviation map displayed the optic disc margin (black line) and center (black cross) information as well as abnormally deviated area from normative database. It was overlaid and registered with optic disc photograph according to the retinal blood vessels. Clinically visible optic disc margin (green dots) was segmented in optic disc photograph and its center (green cross) was calculated by averaging the coordinates of margin. In this case, clinically visible optic disc center was nasally displaced 1 pixel from the center of OCT image.</p

Characteristics of healthy subjects.

<p>Characteristics of healthy subjects.</p