Change of parapapillary atrophy during axial elongation - β-zone parapapillary atrophy induced by mechanical stretching: Boramae Myopia Cohort Study

Abstract

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 every 6 months for 2 years. 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 optic disc opening (DO) were manually delineated. The area and position of β-zone PPA were calculated as the differences from those of the RPEO and DO, 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 area, position, and composition of β-zone PPA were compared between the first and final visits.

Results : β-zone PPA increased in 35 eyes (76%), and was associated with increased RPEO and decreased DO. β-zone PPA enlargement was correlated with the direction and extent of vascular trunk dragging (P=0.014) and showed a marginally significant correlation with axial elongation (P=0.056). In all of the cases showing β-zone PPA enlargement, γ-zone PPA was 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 PPA and β_BM during axial elongation.

Conclusions : Enlargement of β-zone PPA in myopia was correlated with the extent and direction of vascular trunk dragging. Since β_BM PPA was observed in childhood and increased with axial elongation, it can be associated with myopia.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.

 

Summary of PPA changes. In most eyes with firm attachment between the RPE and BM, γ-zone PPA appears and the RPEO equals the BMO. Some of the eyes show alignment failure and lack a firm attachment between layers, which results in β_BM γ-zone PPA of the crescent shape. Also in this case, axial elongation leads mostly to the enlargement of γ-zone PPA. In the case of severe dragging, however, eyeball growth could not be compensated by the shift of the outer-walls, requiring, rather, the change of retinal curvature (gray arrows). This regional change will increase the distance to be covered by the RPE while it is more firmly attached at the foveal side than at the juxtapapillary side with pre-existing β_BM γ-zone PPA. As a result, an elastic membrane, BM within β-zone PPA, may increase to compensate for this.