Transverse Separation of the Outer Retinal Layer at the Peripapillary in Glaucomatous Myopes

The Shape of Posterior Sclera as a Biometric Signature in Open-angle Glaucoma: An Intereye Comparison Study

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Purpose:

To characterize intereye differences in posterior segment parameters and determine their significance in open-angle glaucoma patients with unilateral damage.

Methods:

Both eyes from 65 subjects without any nerve damage and 43 patients undergoing treatment for unilateral open-angle glaucoma were included in this study. A 12.0×9.0×2.6 mm volume of the posterior segment in each eye was scanned with swept-source optical coherence tomography. Coronally reconstructed optical coherence tomography images were analyzed to determine the deepest point of the eye (DPE), which we then calculated the distance (Disc-DPE distance), depth (Disc-DPE depth), angle (Disc-DPE angle) from the optic disc center to the DPE. Posterior pole shape was analyzed measuring the posterior pole-cross-sectional area, posterior pole-horizontal width (PP-HW), and posterior pole-vertical width) of the posterior pole. These measurements and their intereye absolute difference (IAD; absolute difference in measurements between the right and left eyes) values were compared between the healthy and unilateral glaucomatous patients.

Results:

The posterior sclera measurements, including the Disc-DPE distance, Disc-DPE depth, and posterior pole-cross-sectional area, were significantly different between the unilateral glaucoma eyes and contralateral healthy eyes (P=0.043, P=0.035, and P=0.049, respectively). By contrast, none of the intereye differences in optic nerve head parameters were significant in the unilateral glaucoma patients. In comparison with the IAD values, the baseline intraocular pressure and PP-HW of the posterior segment showed significant differences between the healthy and the unilateral glaucoma patients (P=0.019 and P=0.036, respectively). A multivariate analysis showed that a larger baseline intraocular pressure IAD [odds ratio (OR), 1.381; P=0.009)] and larger PP-HW IAD (OR, 1.324; P=0.032) were significantly associated with the presence of glaucoma.

Conclusions:

Compared with the fellow healthy eyes, glaucomatous eyes had larger and more steeply curved posterior poles, which represent a structural variation of the posterior sclera that might be associated with glaucomatous optic neuropathy.

Controversies in the association of parapapillary atrophy with glaucoma

Parapapillary atrophy is a condition which is seen in around 70% of normal individuals. Classically divided into zone alpha and beta, recently, it has been further categorized into zone gamma and delta. Some of these zones of parapapillary atrophy are more prevalent and larger in size in glaucoma patients. Studies have also found the rate of progression of glaucomatous change to be faster in patients with this anomaly. This condition is of clinical significance in glaucoma suspects, as it could be another pointer indicating potential risk of converting to glaucoma. On the contrary, there are other studies which question the relevance of these clinical features in glaucoma patients. In the light of these conflicting reports, it becomes an interesting exercise to explore this controversial area further. This review attempts to determine the role of parapapillary atrophy and its relevance with glaucoma. With this purpose, an online search for this term was conducted on search engines such as PubMed, Google Scholar, and others.