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Editors Selection IGR 14-2

Diagnostic Methods: OCT: Patterns of RNFL progression

Comment by Eytan Blumenthal on:

50501 Retinal Nerve Fiber Layer Imaging with Spectral-domain Optical Coherence Tomography: Patterns of Retinal Nerve Fiber Layer Progression, Leung CK; Yu M; Weinreb RN et al., Ophthalmology, 2012; 119: 1858-1866

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Each time we analyze a diagnostic printout for glaucoma, be it a visual field or an imaging scan, we ask ourselves two questions: is this glaucoma?, and has the patient progressed? We have fairly good clinical judgment about how glaucomatous damage looks. But what do we really know about patterns of progression? Just like we often look at a single scan and think, 'this doesn't look like glaucoma' or, 'this scan needs repeating since the pattern doesn't make sense', we ought to be able to look at change seen in a series of scans and comment wisely. But to acquire this clinical judgment we must first learn how glaucomatous progression typically manifests in imaging. Leung et al., in a pivotal study, address this fundamental issue. They collected VF's and SD-OCT from 186 eyes of 103 established patients, at four-month interval over three years, and from them, identified 28 eyes (15%), that have progressed per OCT. Three patterns of progression included widening of existing RNFL defect (86%, by far the most common pattern), deepening of existing RNFL defect (7%), and appearance of a new RNFL defect (18%). Not surprisingly, only 46% of eyes who progressed on OCT also demonstrated VF progression during this time window. An overlay map demonstrates nicely that the single location in the posterior pole which demonstrated, by far, the most progression, was located infero-temporally to the disc, some two mm from the disc center.

Only 46% of eyes who progressed on OCT also demonstrated VF progression

The authors highlight that as opposed to most imaging studies that rely on a single ('double-hump') narrow ring of data, this study analyzed the entire two-dimensional color-coded map of the poste- rior pole, which contains far more information. On a personal note, to improve your clinical judgment of structural progression it would be beneficial not to stop here, but to view the figures in this article, as they illustrate nicely how typical wedge-shaped RNFL defects progress over time.

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