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Editors Selection IGR 11-2

Clinical Examination Methods: Parapapillary Atrophy Zones

Comment by Marcello Nicolela on:

72865 Measurements of the parapapillary atrophy zones in en face optical coherence tomography images, Miki A; Ikuno Y; Weinreb RN et al., PLoS ONE, 2017; 12: e0175347

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Diagnosing glaucoma in myopic eyes can be challenging, particularly in eyes with significant optic nerve tilt and pronounced peripapillary atrophy (PPA). Modern imaging and visual field tests aren't of great benefit in helping this diagnosis, as myopia alone can cause OCT abnormalities and visual field defects. Recent studies have demonstrated that what was traditionally described as beta type of PPA (a hypopigmented atrophic area bordering the edges of the optic disc), can be distinguished in two distinct subtypes, based on OCT findings: the OCT defined beta type, where RPE is absent but Bruch's membrane is present, and the gamma type, where both RPE and Bruch's membrane are absent. Some authors reported that beta type of PPA has greater association with glaucoma and gamma type has greater association with myopia.

Miki et al. reported on a new method of assessing PPA in SS-OCT images, by performing en face measurement, therefore eliminating the possible measurement error of projecting the PPA borders identified at the level of the RPE / Bruch's membrane into the red-free images. Their study confirmed previous finding that beta PPA was associated with glaucoma and age, whereas gamma zone was associated with myopia. Their new method of measuring PPA is elegant, but it would be useful to compare with measurements of PPA done more traditionally on red free images, to evaluate the magnitude of the difference between the two methods. One problem of their study is that the control individuals were not myopic. In order to truly evaluate the relevance of OCT defined PPA types in identifying glaucomatous damage in myopic individuals, a myopic control group should be included, allowing for a more realistic evaluation of the diagnostic accuracy of the subtypes of PPA defined by OCT.

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