Peripapillary Atrophy in Myopic Eyes: Comparison of Gamma to Beta Zone Ratio Between Those With and Without Glaucoma

We read with great interest the recently published article by Vianna and colleagues,¹ which investigated differences in peripapillary atrophy (PPA) distribution between myopic patients with and without glaucoma. 

The major outcome of the study was the comparison of beta and gamma PPA areas between myopic eyes with and without glaucoma. In disagreement with previously published data,² the authors didn't find significant differences in the distribution of absolute values of each type of PPA, with a significant overlap between groups. Looking carefully at the study methodology and results, one can note that total PPA areas differed between groups. In this context, a proportional analysis (such as a ratio) between gamma and beta PPA areas could be more appropriate. For instance, if we compare the proportion of gamma zone PPA between groups, the gamma to beta zone PPA ratio would be 0.28 and 0.56 in eyes with and without glaucoma, respectively, yielding a 100% difference. This is twice the difference reported by the study when solely absolute values were used (0.28 vs. 0.42 mm²; a 50% difference). We believe this fact might have diminished the reported differences between eyes with and without glaucoma. 

With that in mind, we believe that two more points could be explored by the authors. First, as the authors have visual field data from these myopic glaucomatous eyes, we suggest investigating possible correlations between PPA proportions and functional status. Second, after this initial cross-sectional analysis, we strongly suggest the authors to follow these patients overtime. Would a smaller proportion of gamma/beta zone PPA be associated with more functional progression in these eyes? 

Although we believe that much still has to be elucidated in the relationship between myopia and open-angle glaucoma³ we congratulate the authors for this laborious imaging study and for adding new information to these challenging cases.