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The paper by Huang et al. (1012) reports on the development of a new method for measuring retinal nerve fiber layer (RNFL) thickness at any location within the retina that has been previously studied with optical imaging such as polarimetry or reflectometry. The new method utilizes en face z-stacks obtained with confocal laser scanning microscopy in retinal tissue labeled with phalloidin and DAPI to measure the thickness of the RNFL. The authors also made some comparisons of the values obtained by this method with measurements of histologic sections. The major innovation in this methodology is the use of phalloidin for labeling the nerve fibers while its value lies in its ability to provide measurements of the RNFL over a large area thus increasing the amount of available data. In addition en face imaging allows easy identification of the exact location from which measurements are derived.
The new method appears to work well and provide images that are of sufficient quality to allow measurement of the RNFL. Blood vessels that also stain for phalloidin can be easily identified. Unfortunately though, the authors provide mostly descriptive data and fail to compare quantitatively measurements obtained with this new method with measurements obtained using polarimetry or reflectometry. Even more importantly, all work is performed in fixed retinal tissue. Given the known effects of fixation on retinal tissue it seems prudent that the initial comparison was performed on fixed tissue. However, what would be most interesting is how this method performs compared with the measurements obtained in vivo. Presumably the authors will present such data in a future report.