Intereye Difference in the Microstructure of Parapapillary Atrophy in Unilateral Primary Open-Angle Glaucoma

To investigate intereye differences in the parapapillary atrophy (PPA) microstructure in unilateral primary open-angle glaucoma (POAG).

Bilateral optic nerves from 172 unilateral POAG patients having clinical PPA shown in infrared fundus imaging were scanned using spectral-domain optical coherence tomography (SD-OCT). Based on the extent of Bruch's membrane (BM) within the PPA area, the PPA was divided into β-zone (area with BM) and γ-zone (area devoid of BM). The width of each type of PPA and disc tilt angle were measured in radial B-scan images. Disc tilt ratio and torsion degree were determined using the radial B-scan and infrared fundus images. Measurements were compared between the glaucomatous and contralateral healthy eyes, and the factors associated with the presence of glaucoma were determined.

The width of β-zone was larger in glaucomatous eyes compared with the contralateral healthy eyes (283.67 ± 157.45 vs. 214.42 ± 145.39 μm, P < 0.001), whereas there were no significant intereye differences in the γ-zone width (P = 0.392). Eyes with POAG had a larger β-zone width (P < 0.001), and larger tilt angle (P = 0.032) compared with the contralateral healthy eyes. In multivariate regression analysis, larger β-zone width (P < 0.001), and lower IOP (P = 0.001) were revealed as significant factors associated with the presence of glaucoma.

The β-zone width was revealed as a significant lateralizing factor for unilateral POAG, whereas the γ-zone was not associated with the presence of glaucoma.