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Editors Selection IGR 13-4

RNFL Imaging: Beta-zone PPA and rate of RNFL thinning

Comment by Jeffrey Liebmann & Christopher Teng on:

47955 (beta)-Zone parapapillary atrophy and the rate of retinal nerve fiber layer thinning in glaucoma, Lee EJ; Kim TW; Weinreb RN et al., Investigative ophthalmology & visual science, 2011; 52: 4422-4427

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β-zone parapapillary atrophy (βPPA) and its relationship with the presence and progression of glaucoma has been well studied. Most publications have evaluated βPPA compared to functional progression, as measured with standard automated perimetry. Because functional progression and structural progression are often not observed to change simultaneously, comparison of βPPA with structural glaucoma progression is also important. In this paper, Lee et al. (1734) use time-domain optical coherence tomography to evaluate whether the presence, size, and increase of βPPA are associated with the rate of retinal nerve fiber layer (RNFL) thickness change. This was a retrospective cohort study and evaluated 202 patients who had at least four previous OCT measurements, 177 normal tension glaucoma and 25 high tension glaucoma patients, and 144 with βPPA and 58 without. The outlines of the optic disc and βPPA were plotted using imaging software and the areas of total optic disc and βPPA were obtained. For OCT measurements, subjects were assessed using the peripapillary fast RNFL program, and OCT values were obtained from 1 to 12 o'clock, and in the global, temporal, superior, nasal and inferior quadrants. Eyes with βPPA showed a significantly faster rate of RNFL thinning than did eyes without βPPA in the inferior quadrant and 7 o'clock sector. Multivariate analysis showed significant influence of the presence of βPPA and the percentage increase in the βPPA to disc area ratio on the rate of OCT RNFL thinning. The authors conclude that the presence and enlargement of βPPA were significantly associated with the rate of progressive RNFL thinning. We commend the authors on their study, which is one of the first to demonstrate the structural relationship of βPPA and RNFL thickness, using OCT imaging. This study further adds to what is known about βPPA and provides additional support for an association between βPPA and glaucoma progression.

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