Right eye of a patient with glaucoma in whom the presence of a clinically visible cilioretinal artery within vertical spectral domain optical coherence tomography (SD-OCT) B-scans provides evidence that the SD-OCT–detected region of Bruch's membrane (BM) overhang adjacent to it is invisible by optic disc stereophotography. A, Optic disc photograph registered to B, infrared image. Inset in A, Magnification of the rectangular area (broken white lines) showing the clinical disc margin determined with stereo-disc photography (green dots) and Bruch’s membrane opening (BMO) determined with SD-OCT B-scans and co-localized to the disc photograph (red dots). C–E, Equidistant line B-scans (shown as x, y, and z in A and B, respectively). The line scan x (shown in C) is at a location where BM is intact, and the line scan z (shown in E) is at a location just inside BM. These B-scans were not part of the study protocol and were obtained additionally (left to right represent bottom to top in A and B). The locations of only x and z are shown in A and B for clarity. BM is continuous in x and y (C and D), indicating that the scan locations are outside the neural canal. Bruch's membrane shows a break in z (E), verifying that the central locations of this scan are inside the neural canal. A cross-section of the cilioretinal artery appears beneath BM in x and y (C and D) and curves around Bruch's membrane overhang in z (E). Because the cilioretinal artery beneath BM is visible in the photograph, it indicates that the temporal region of BM overhang is clinically transparent and invisible. Because BMO in this region is internal to the clinical disc margin and clinically invisible, conventional clinical examinations overestimate the amount of remaining neuroretinal rim tissue. Cra = cilioretinal artery.