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This manuscript represents another in a series of investigations of the relationship between structural (Optical Coherence Tomography [OCT]) and functional (visual field sensitivity) losses in glaucoma by this group of investigators. In this study, however, the authors compare the relationship between visual field sensitivity loss (Humphrey Field Analyzer 10-2 stimulus presentation pattern) and retinal ganglion cell layer thickness (frequency domain OCT) for localized regions of the macula. The authors report that structural and functional losses are strongly correlated within approximately 7.2 degrees of the fovea and are in accordance with a linear model, but become worse beyond that point.
Overall, this study has been performed very carefully and was well organized. The authors use an established linear model to evaluate structure-function relationships, and pay attention to many details (such as correction for displacement of retinal ganglion cell bodies around the fovea) to obtain accurate comparisons of structure and function in the macula. It is also encouraging that the authors used Total Deviation values rather than Pattern Deviation assessments because this has been reported to be a better indicator of early glaucomatous visual field loss and progression.1,2 Contrary to some dogma associated with the management of glaucoma, an important finding of this investigation is that the macula is affected by glaucomatous damage not only at late stages of the disease, but also at earlier stages of glaucoma as well. This knowledge was previously impeded by the lack of appropriate techniques for assessing early glaucomatous damage to macular mechanisms. In this view, frequency-domain OCT provides a wealth of informative structural data, but current visual field procedures such as the 10-2 stimulus presentation pattern provide a limited, sparse assessment of visual function properties. There is clearly a need for fine detail mapping of the macular visual field and accurate, precise control of eye and head movements for future advances in the assessment of damage to the macular region in glaucoma.