Figure 6.

Four illustrative cases (A–D) demonstrating the impact of variations in optic nerve head (ONH) anatomy on neuroretinal rim measurements. Infrared image from anatomical SD-OCT (left), registered optic disc photograph (center) and SD-OCT B-scans (right). Dashed white lines indicate the orientation of the radial B-scans and solid white lines indicate the section of the B-scans shown. (A) Right ONH of a glaucoma patient with extension of BMO internal to the clinically visible DM in all sectors except temporally resulting in DM-HRW being erroneously larger than BMO-HRW or BMO-MRW. (B) Significant mismatch between DM and BMO in the left ONH of a glaucoma patient. In the radial section shown in the temporal sector, DM-HRW is erroneously larger than BMO-HRW; however, because the trajectory of the nerve fiber layer is more parallel to the DM and BMO plane, BMO-MRW is considerably smaller. (C) Right ONH of a glaucoma patient with internal extension of BM in the nasal half and the superior temporal sector of the disc. Although the DM and BMO almost coincide in the radial section shown in the temporal sector yielding similar DM-HRW and BMO-HRW measurements, BMO-MRW is substantially smaller. (D) Left ONH of a healthy subject with significant mismatch between DM and BMO, with DM internal to BMO in the inferior temporal quadrant and BMO internal to DM in the remainder of the disc. Although the DM and BMO almost coincide in the radial section shown with similar DM-HRW and BMO-HRW measurements, BMO-MRW is substantially smaller owing to the trajectory of the nerve fiber layer.