Beta and Gamma Peripapillary Atrophy in Myopic Eyes With and Without Glaucoma.

Abstract

To determine whether beta and gamma peripapillary atrophy (PPA) areas measured with optical coherence tomography (OCT) enhances glaucoma diagnosis in myopic subjects. We included 55 myopic glaucoma patients and 74 myopic nonglaucomatous controls. Beta-PPA comprised the area external to the clinical disc margin, with absence of retinal pigment epithelium and presence of Bruch's membrane. Gamma-PPA comprised the area external to the disc margin, with absence of both RPE and Bruch's membrane. OCT scans colocalized to fundus photographs were used to measure PPA, choroidal thickness, border tissue of Elschnig configuration, optic disc area, and optic disc ovality. Beta-PPA area was larger in glaucoma patients compared with controls (median [interquartile range], 1.0 [0.66-1.53] mm2 and 0.74 [0.50-1.38] mm2, respectively), whereas gamma-PPA was smaller in glaucoma patients compared with controls (0.28 [0.14-0.50] mm2 and 0.42 [0.17-0.74] mm2, respectively). However, the distributions of both beta- and gamma-PPA in the two groups overlapped widely. The areas under the receiver operating characteristic curve of beta- and gamma-PPA areas were 0.60 and 0.59, respectively. Larger beta-PPA area was associated with larger disc area, thinner choroidal thickness, longer axial length, less oblique border tissue configuration, older age, and greater disc ovality. Larger gamma-PPA area was associated with greater disc ovality, more oblique border tissue configuration, and longer axial length. Subclassifying PPA with OCT into beta and gamma zones reveals association with different covariates, but does not enhance the diagnostic performance for glaucoma in a population of predominantly Caucasians myopic subjects.