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Editors Selection IGR 16-4
Anatomical Structures: Peripapillary Atrophy and Glaucoma Progression
Comment by Jost Jonas on:
66313 Microstructure of Peripapillary Atrophy and Subsequent Visual Field Progression in Treated Primary Open-Angle Glaucoma, Yamada H; Akagi T; Nakanishi H et al., Ophthalmology, 2016; 123: 542-551
According to recent histological and clinical studies, the parapapillary region can be divided into a peripheral alpha zone characterized by the presence of Bruch's membrane and presence of irregularly structured retinal pigment epithelium (RPE) (appearing upon ophthalmoscopy as irregular hyperpigmentation and hypopigmentation); a beta zone, characterized by the presence of Bruch's membrane and absence of RPE (appearing upon ophthalmoscopy as whitish area with visible large choroidal vessels (the choriocapillaris is closed for most parts of beta zone) and visible sclera); and a gamma zone characterized by the absence of Bruch's membrane (and thus by the absence of RPE and choriocapillaris).
Differentiation between beta and gamma zone may increase the diagnostic value of assessing the parapapillary region in glaucoma
In highly myopic eyes, gamma zone can further be subdivided into a central delta zone covering the region between the optic disc border (defined by the peripapillary ring as the continuation of the optic nerve pia mater and the border tissue of Elschnig and Jacoby) and the merging line of the optic nerve dura mater with the posterior sclera. Delta zone is the equivalent for the elongated and thinned peripapillary scleral flange in highly myopic eyes which is the bridge between the posterior sclera and the lamina cribrosa and which forms the end of the orbital cerebrospinal fluid space. Yamada and colleagues examined in their retrospective cohort study the relationship between the microstructure of the so called parapapillary beta zone and subsequent visual field progression in 129 patients with primary open-angle glaucoma. They divided their beta zone into a beta zone with Bruch's membrane (i.e. the beta zone as described above) and a beta zone without Bruch's membrane (what is the gamma zone as described above).
In a follow-up of at least two years, eyes with beta zone (with Bruch's membrane) as compared to eyes with gamma zone showed a significantly higher rate of glaucoma progression. In contrast, gamma zone was associated with a slower progression of glaucomatous visual field defects. These results are in agreement with previous histological and clinical studies showing that beta zone is associated with glaucoma (and gamma zone with high axial myopia). Differentiation between beta and gamma zone may increase the diagnostic value of assessing the parapapillary region in glaucoma.
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