Subject specific angular waist of the optic nerve head nerve fiber layer allows follow up detection of local nerve fiber bundle loss

Purpose To clarify if frontal plane angular Pigment epithelium central limit‐ Inner limit of the retina Minimal Distance (PIMD) measured with OCT has enough specific angular structure for detection of change of specific angular segments of PIMD over time within glaucoma subjects. Methods A Topcon OCT‐2000 was used for capture of the 3D representations of the ONH. from one eye of each of totally 13 subjects with early stage primary open angle glaucoma. Altogether, 3 volumes were captured at two occasions within 3 months. PIMD was semi‐automatically segmented in each volume in 500 equally spaced angular segments distributed over 2Pi in the frontal plane. Results Plots of the angular distribution of PIMD for all subject revealed specific low angular frequency overlaid with higher intermediate angular frequencies specific for each subject. High angular frequencies appeared similar for all subjects. A fast Fourier transform of the angular PIMD revealed a high to low frequency content ratio, 0.12, consistent for all segmentations of PIMD‐2Pi. The rotational displacment of angular PIMD in the frontal plane among segmentations, volumes and occasions was determined with cross‐correlation. Then, all PIMD‐2Pi were phase adjusted over segments, volumes and occasions. Finally, the rotation of PIMD‐2Pi was adjusted to a standard rotation. This allows comparison of angular segments of PIMD‐2Pi between visits. The magnitude of different sources of variation were estimated with analysis of variance. Conclusions Angular correction in the frontal plane of recordings of angular PIMD of the ONH allows comparison of angular segments of PIMD‐2Pi. This substantially increases the resolution of of an angular segment of PIMD. The resulting precision suggest that detection of an angular segment of PIMD is associated with better resolution than Humphrey visual field MD.