PMC

Histologic sagittal section of the optic nerve head of a rhesus macaque, showing the BMO (top, unlabeled; bottom, labeled), NC (boundary demarcated by a black line) and NCO. Inset: RPE and BM.

Generation of the OCT NCO point cloud for monkey 23511 (OS). Top image: en face (transverse view of SD-OCT volume). All 80 NCO points (red glyphs) are shown, having been delineated in all the 40 radial sections at 4.5° intervals. Middle image: the en face view has been rotated in space, so as to demonstrate the appearance of the NCO point cloud in three dimensional space. Bottom image: an alternative view of the NCO point cloud in 3-D space; the delineated BM points (orange lines) are also shown.

Generation of a histomorphometric NCO point cloud in monkey 23540 (OD eye). Top image: en face (transverse) view of histomorphometric reconstruction. All 80 NCO points (red glyphs) are shown, having been delineated in all the 40 radial sections at 4.5° intervals. The center of rotation is marked by a green glyph. Middle image: the en face view was rotated in space, so as to demonstrate the appearance of the NCO point cloud in three dimensional space. Bottom image: An alternative view of the NCO point cloud in 3-D space; the delineated BM points (orange glyphs) are also shown.

Fitted NCO plane and ellipse within an SD-OCT volume from the left eye of monkey 23511. (A) The NCO points are shown in space; (B) a plane has been least-squares fit to the NCO points; (C) the y-axis scale has been magnified to exaggerate the distance of the NCO points from the fitted plane (shown by the black lines). The plane error for each eye is calculated from the mean of these distances. (D) The NCO points have been projected onto the level of the fitted plane; these “planar” NCO points are viewed in the en face orientation. (E) An ellipse has been least-squares fit to the “planar” NCO points. Two black axes are shown within the ellipse, demonstrating the major (longer) and minor (shorter) axes. Eccentricity is derived from the ratio of the major ellipse axis to the minor ellipse axis.

Delineation of the NCO within histomorphometric (top two images) and SD-OCT (bottom two images) reconstructions. These images are Multiview software screen captures. Top image: Digital, radial sagittal section of a histomorphometric reconstruction section (90° or horizontal in location), taken from the right eye of monkey 23540, a 9-year-old female rhesus macaque. Middle top image, red triangles: the location of the NCO (as applied within Multiview software) which in this eye is coincident with the BMO. Middle bottom image: sagittal view of a radial interpolated SD-OCT section (90° location), taken from the left eye of monkey 23511, a 12-year-old male rhesus macaque. Bottom image: the same as the middle image, but with NCO points marked (red glyphs, as applied within Multiview software). The posterior surface of the RPE/BM complex is also marked (orange lines and glyphs). The NCO points are at the innermost aspect of this surface.

NCO point cloud (top) generated from the SD-OCT volume of the left eye of monkey 25904, a 1-year-old female rhesus macaque. Middle: RPE/BM complex delineated by orange lines. The NCO points relative to their fitted plane viewed from temporal to the disc, (OD configuration, superior left and inferior right) are depicted below. Bottom: NCO plane error (defined as the average of the shortest distance to the plane for each NCO point) is 18 μm. Unlike in , in this eye, the NCO points are clearly contiguous suggesting a gently bowed structure that is symmetrical about the vertical axis. Although method error still contributes to plane error in this eye, biological nonplanarity is most likely the principal component. Biological nonplanarity that is delineated reproducibly over time will still provide a stable fitted plane for a zero reference.

NCO point cloud (top) generated from the histomorphometric reconstruction of the right eye of monkey 675D, a 31-year-old male rhesus macaque. The NCO points relative to their fitted plane viewed from temporal to the disc, (OD configuration, superior left and inferior right) are depicted below. NCO plane error (defined as the average of the shortest distance to the plane for each NCO point) is 15 μm. Although the NCO points appear randomly distributed above and below the plane (middle), when the nasal and temporal points are displayed with different colors (bottom: temporal points [green], nasal points [orange]) their distribution can be seen to continuously follow a structure that is slightly twisted. This finding is easily seen when the points are visualized in 3-D but is difficult to demonstrate in two dimensions. Although method error contributes to plane error, so too does biological nonplanarity. Biological nonplanarity that is delineated reproducibly over time will still provide a stable fitted plane for a zero reference.