In-vivo microstructural anatomy of beta-zone parapapillary atrophy in glaucoma

To assess the microstructural anatomy of clinical β-zone parapapillary atrophy (βPPA) by using Fourier-domain optical coherence tomography (FD-OCT).

Color photographs and horizontal cross-sectional FD-OCT images of the optic disc and parapapillary retina were obtained in 24 eyes (24 patients with glaucoma or suspected glaucoma) with βPPA. The distances between the temporal disc margin and parapapillary landmarks (clinical βPPA margin and the edges of the retinal pigment epithelium [RPE], Bruch's membrane [BM], and the photoreceptor inner/outer segment [IS/OS] junction) were measured in 5 equally spaced horizontal meridians (total, 120 meridians).

The mean age was 56 ± 13 (SD) years. In the five meridians, the mean distances from the temporal disc margin to the temporal βPPA margin and the edges of RPE, BM, and the IS/OS junction were 388 ± 173, 371 ± 174, 214 ± 204, and 502 ± 167 μm, respectively. The RPE edge corresponded to the βPPA margin in 78 (65%) of 120 meridians and ended within the βPPA in 42 (35%) of 120 meridians. The BM edge corresponded to the RPE edge in 13 (11%) of 120 meridians and was closer to the disc in 107 (89%) of 120 meridians. The disc margin corresponded to the BM edge in 20 (17%) of 120 meridians and to the edge of the border tissue of Elschnig in 100 (83%) of 120 meridians. The IS/OS junction edge was farther from the disc than the temporal βPPA margin was in all 24 eyes.

The βPPA was not completely denuded of RPE, and there was a crescent-shaped area of photoreceptor degeneration or atrophy peripheral to the βPPA. The termination of the border tissue of Elschnig constituted the temporal disc margin in most eyes with βPPA.