Change of β-zone parapapillary atrophy during axial elongation: Boramae myopia cohort study report 3

PURPOSE. To investigate changes of β-zone parapapillary atrophy (PPA) during axial elongation. METHODS. Change of β-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 β-zone PPA was calculated as the differences from those of the RPEO and CDM, respectively. The β-zone PPA was further differentiated into β _BM PPA (β-zone PPA with Bruch’s membrane [BM]) and γ-zone PPA (β-zone PPA without BM). The change of β-zone PPA was compared between the first and final visits. RESULTS. The area of β-zone PPA increased in 35 eyes (76%). This increase was associated with RPEO area increase and CDM area decrease. The center of β-zone PPA moved along the direction of vascular trunk dragging, but to a lesser extent. The β-zone PPA enlargement was correlated with the extent of vascular trunk dragging (P = 0.014). In all eyes with β-zone PPA increase, the γ-zone portion had increased. Even in childhood, β _BM PPA existed next to their γ-zone PPA in 11 eyes (24%), including 4 eyes that showed increase of both γ-zone and β _BM portion during axial elongation. CONCLUSIONS. Enlargement of β-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.