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Editors Selection IGR 18-1

Anatomical structures: Do laminar abnormalities explain disc hemorrhage ?

Comment by Ki Ho Park on:

69353 Optic Disc Hemorrhages and Laminar Disinsertions in Glaucoma, Sharpe GP; Danthurebandara VM; Vianna JR et al., Ophthalmology, 2016; 123: 1949-1956

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Previous studies have demonstrated a significant association between disc hemorrhage (DH) and the presence of laminar defects as well as a spatial correlation between the two. The current paper by Sharpe et al. is the product of a well-designed and methodologically sound study. They enrolled 52 eyes of 46 open-angle glaucoma patients with DH and 52 eyes of 46 patients without DH matched for age and visual-field mean deviation. The SD-OCT radial cross-sectional images of the optic nerve head were reviewed, by a masked observer, for the presence and location of the laminar disinsertion. The laminar disinsertion was found in 96% of eyes with DH and in 52% of eyes without DH, which results are quite similar to a recent SS-OCT-based report:¹ 80.6% (58 of 72 eyes) showing laminar defect in eyes DH; 39.7% (25 of 63 eyes) in eyes without DH.

We still do not know clearly whether laminar defect is a result of DH and subsequent tissue remodeling or the cause of DH

Thus it seems quite evident that in open-angle glaucoma, DH+ eyes might have about twice the chance of laminar defect as DH- eyes. The strengths of the current study are that the authors used objective grading scores of laminar disinsertion and the subjects were enrolled, for eyes with DH+ or DH-, regardless of the laminar-structural deformity. Further, the results of the current study might partially explain why DH occurs more frequently at the disc margin.

However, we still do not know clearly whether laminar defect is a result of DH and subsequent tissue remodeling or the cause of DH. The lower-pressure subtype tends to support the former hypothesis, and the high-pressure, mechanical-stress-related subtype the latter. Prospective long-term longitudinal studies investigating lamina cribrosa change before and after DH could provide more information regarding the mechanisms associated with DH and laminar defect.

Laminar disinsertions occurred twice as frequently in eyes with DH

Readers might be curious about whether there was, additionally to the peripheral laminar disinsertion, any non-peripheral laminar defect. As demonstrated by the poor spatial concordance between DHs and laminar disinsertions of the current study, eyes can have DHs that are remote from the laminar disinsertions. In fact, DH does not always occur at the disc margin but, sometimes, in the non-peripheral laminar region or retinal nerve fiber layer outside of the disc. As explained in the paper's Discussion, there are multiple mechanisms of DH, some dependent on laminar disinsertion and others less so.

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