Change of β-Zone Parapapillary Atrophy During Axial Elongation: Boramae Myopia Cohort Study Report 3

PURPOSE. To investigate changes of beta-zone parapapillary atrophy (PPA) during axial elongation. METHODS. Change of beta-zone PPA was evaluated by spectral-domain optical coherence tomography (SD-OCT) in myopic children for 2 years, prospectively. Using the infrared images acquired by a fixed scan circle in the glaucoma progression analysis (GPA) mode, the retinal pigment epithelial opening (RPEO) and the clinical disc margin (CDM) were manually delineated. The area and position of beta-zone PPA was calculated as the differences from those of the RPEO and CDM, respectively. The beta-zone PPA was further differentiated into beta(BM) PPA (beta-zone PPA with Bruch's membrane [BM]) and gamma-zone PPA (beta-zone PPA without BM). The change of beta-zone PPA was compared between the first and final visits. RESULTS. The area of beta-zone PPA increased in 35 eyes (76%). This increase was associated with RPEO area increase and CDM area decrease. The center of beta-zone PPA moved along the direction of vascular trunk dragging, but to a lesser extent. The beta-zone PPA enlargement was correlated with the extent of vascular trunk dragging (P = 0.014). In all eyes with beta-zone PPA increase, the gamma-zone portion had increased. Even in childhood, beta(BM) PPA existed next to their czone PPA in 11 eyes (24%), including 4 eyes that showed increase of both gamma-zone and beta(BM) portion during axial elongation. CONCLUSIONS. Enlargement of beta-zone PPA during axial elongation was affected by the extent and direction of vascular trunk dragging, thus implicating disproportionate growth between the retina and sclera.