Figure 3.
Although regions of internally and externally oblique BTE are defined by the offset of OCT BMO relative to OCT ASCO, PCT measurements within these regions are not included in the normative values of this report. (A) Color optic disc photo of the study eye of subject FDA287, with colocalized OCT ASCO (blue) and OCT BMO (red) points. The location and orientation (B1–B2) and (D1-D2) of the cropped B-scans shown in B, C and D, E are shown. (B) Cropped superior-nasal B-scan in a region of internally oblique BTE, (B1-B2) shown in A and delineated in (C). Note that BMO is “internal” to ASCO (or closer to the center of the disc). Note also that the suggestion of a juxta-scleral canal posterior ciliary vessel entering the choroid from the sclera (red dots). (D) Cropped inferior-temporal B-scan in a region of externally oblique BTE (D1-D2) shown in A and delineated in (E). Note that BMO is “external” to ASCO (or farther from the center of the disc). Although externally oblique border tissues do not represent atrophy in any form, they are commonly referred to as gamma peripapillary atrophy in the clinical55 and OCT4,56,57 literature. (F) The clinical extent of internally (blue) and externally (pink) oblique BTE in a healthy study eye with mild myopia (spherical equivalent −4.25D, axial length 25.13 mm). In this cross-sectional study, PCT measurements within the regions of BTE obliqueness were not included in the normative values because when present the density of the border tissues themselves and the adjacent choroidal septa made the presence of active choroidal vasculature difficult to determine and because the occurrence and regional distribution of internally and externally oblique border tissues are not consistent among all human eyes.20 However, PCT can be measured relative to the ASCO within both forms of oblique border tissue regions, and the individual eye longitudinal change within these regions may be clinically important.