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Editors Selection IGR 16-4
Anatomical Structures: Peripapillary atrophy
Comment by Sung-Chul Park on:
53729 Differentiation of Parapapillary Atrophy Using Spectral-Domain Optical Coherence Tomography, Kim M; Kim TW; Weinreb RN et al., Ophthalmology, 2013; 120: 1790-1797
β-zone parapapillary atrophy (β-PPA) is associated with development and progression of glaucoma, but its relationship with temporal crescent in myopic optic discs has been unclear. β-PPA was originally explained as an absence (atrophy) of the retinal pigment epithelium (RPE) but has recently been investigated with regard to Bruch's membrane (BM) after Park et al.1 reported the locations of RPE and Bruch's membrane separately using spectral-domain optical coherence tomography (SD-OCT) within the β-PPA area.
β-PPA with intact BM may be an age-related atrophic change and that β-PPA with no BM may result from elongation of the globe
Kim et al. categorized β-PPA based on its relationship with BM using SD-OCT in patients with primary open-angle glaucoma (POAG). They analyzed horizontal SD-OCT scans of the middle one-third region of the optic discs with temporal β-PPA and found that POAG eyes with β-PPA completely covered by BM had older age, shorter axial length and greater circumferential extent of β-PPA than those with β-PPA denuded of BM. Additionally, > 90% of eyes with β-PPA completely covered by BM had internally oblique or non-oblique border tissue of Elschnig, whereas > 90% of eyes with β-PPA denuded of BM had externally oblique border tissue.
These findings suggest that β-PPA with intact BM may be an age- related atrophic change and that β-PPA with no BM may result from elongation of the globe. That is, parapapillary RPE atrophy associated with older age may leave the BM intact. In contrast, the RPE-BM complex may slide away from the optic nerve head as the scleral canal and border tissue of Elschnig are stretched and externalized in myopic eyes. This concept is further supported by the appearance of β-PPA. The β-PPA completely covered by BM had irregular, lobulated borders, whereas the β-PPA with no BM had smooth borders. This morphologic classification of β-PPA based on the presence of BM is not new. Jonas et al.2 and Dai et al.3 investigated β-PPA area with no BM (termed as 'gamma zone') using histological sections and SD-OCT scans of patients with and without glaucoma and demonstrated that β-PPA area with no BM was associated with increasing myopia but not with glaucoma, whereas β-PPA area covered by BM was associated with glaucoma. In the study by Kim et al., the influence of glaucoma on the β-PPA microstructures was not investigated because they included only patients with POAG but not normal subjects. These articles suggest that SD-OCT-guided localization of the BM within the β-PPA may be useful in the risk assessment for development and progression of glaucoma.
References
- Park SC, De Moraes CGV, Tello C, Liebmann JM, Ritch R. Invivo microstructural anatomy of β-zone parapapillary atrophy in glaucoma. Invest Ophthalmol Vis Sci 2010; 51(12): 6408-6413.
- Jonas JB, Jonas SB, Jonas RA, Holbach L, Dai Y, Sun X, Panda-Jonas S. Parapapillary atrophy: histological gamma zone and delta zone. PLoS One 2012; 7(10): e47237.
- Dai Y, Jonas JB, Huang H, Wang M, Sun X. Microstructure of parapapillary atrophy: beta zone and gamma zone. Invest Ophthalmol Vis Sci 2013; 54(3): 2013-2018.
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