En Face Optical Coherence Tomography Imaging of Beta and Gamma Parapapillary Atrophy in High Myopia

Abstract

Recent studies have suggested that OCT-based classification of parapapillary atrophy (PPA) may be helpful in distinguishing glaucomatous from myopic optic disc changes. However, the pathologic implications of PPA may be different in highly myopic eyes that exhibit optic disc deformations distinct from low-to-moderate myopia. Therefore, we conducted the current study to investigate factors associated with OCT-defined PPA zones measured in en face reconstructed swept-source OCT (SS OCT) images in highly myopic eyes. Retrospective, cross-sectional study. Seventy-seven eyes of 55 subjects with high myopia (spherical equivalent refractive error ≤ -8 diopters or axial length ≥26.5 mm) were included. Forty-nine eyes of 33 subjects had open-angle glaucoma (MG group), and 28 eyes of 22 did not (M group). The beta zone and the gamma zone PPA areas were measured in en face images reconstructed from 3-dimensional SS OCT volumetric scans. Relationships between the PPA areas and patient characteristics such as glaucoma, axial length, and age were evaluated using multivariate mixed-effects models. The diagnostic capability of each PPA zone area for detecting glaucoma was assessed with the receiver operating characteristic (ROC) curve analysis. Main outcome measures were areas of the beta zone and the gamma zone PPA measured in en face OCT images and factors associated with each PPA area. Average ± standard deviation area of the beta and the gamma zone was 1.1±1.1 and 1.1±1.1 mm2. The gamma zone was positively correlated with axial length (P= 0.006) and age (P= 0.04951) but not with glaucoma (P= 0.776). The beta zone was positively correlated with both axial length (P= 0.039) and glaucoma (P= 0.011). The areas under the ROC curve of the beta zone and the gamma zone areas were 0.686 and 0.560, respectively. The OCT-defined beta zone was associated with glaucoma and axial length, whereas the gamma zone was correlated with axial length but not with glaucoma, in highly myopic eyes. The OCT-based classification showed poor diagnostic performance for glaucoma. Relationships between PPA areas and baseline clinical factors may be different between high myopia and non-high myopia.