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Editors Selection IGR 15-4

Anatomical Structures: Lamina Cribrosa

Comment by Michael Kook on:

55398 Factors associated with focal lamina cribrosa defects in glaucoma, Park SC; Hsu AT; Su D et al., Investigative Ophthalmology and Visual Science, 2013; 54: 8401-8407

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In this article by Park et al. using serial EDI OCT, glaucomatous eyes with focal lamina defects were identified and compared with those without, and clinical factors associated with focal lamina defects were further investigated. In doing so, the authors report clinically relevant elements that are linked to focal LC defects in glaucoma patients with various disease severity. These include disc hemorrhage, a diagnosis of normal-tension glaucoma (NTG), and more advanced glaucoma status. This study provides important data illustrating that focal LC defects are relatively common in glaucoma patients (45%), at least in authors' series, despite the use of strict definition of focal LC defects (defined as 'full-thickness' holes or disinsertions). Therefore, it suggests that LC may serve as a biomarker or surrogate structural parameter, independently or in conjunction with other conventional parameters such as neural rim area, retinal nerve fiber layer (RNFL) thickness, or retinal ganglion cell count, to diagnose and possibly monitor glaucoma. Although the data undoubtedly suggest the 'association' of focal LC defects with disc hemorrhage, it does not fully explain the cause-and-effect relationship between the two as disc hemorrhage can occur in a variety of presentation pattern and different location that may not be consistent in a temporal manner or in proximity with focal LC defect location in glaucoma. Prospective, longitudinal study can provide more clear insight into the temporal sequence between the two and an answer to this enigma. Important imitation of the study and use of LC as a structural parameter in general, as pointed out by the authors, should be considered in the clinical interpretation of this study. The limitation is that focal lamina defects were based on the subjective call using rigorous criteria for focal defects to avoid normal variants or obscure images.

If LC is to be considered as a structural parameter in glaucoma, the visualization of focal LC defects, particularly at early stage, must be more reliable and repeatable to avoid bias and controversy with further improvement in imaging technology

As early glaucomatous optic disc changes begin with subtle localized structural changes, clinical factors associated with focal LC defects an early stage still remain uncertain as mentioned by the authors. Conceivably, this makes one wonder whether or not the 'full-thickness' prominent focal L/C defects identified in the study are the consequences of advanced glaucoma as indicated by worse VF MD and PSD. Finally, if LC is to be considered as a structural parameter in glaucoma, the visualization of focal LC defects, particularly at early stage, must be more reliable and repeatable to avoid bias and controversy with further improvement in imaging technology. The authors should be commended for expanding further knowledge on glaucoma pathogenesis using EDI OCT derived LC as a novel biomarker.

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