Abnormalities in the appearance of the nerve fiber layer can indicate the presence of optic nerve atrophy, but a major problem has been the difficulty of visualizing the nerve fiber layer in some individuals. By selectively illumimating the white nerve fiber layer in comparison with the red retinal pigment epithelium and choroidal background, red-free light increases the visibility of the nerve fiber layer. Compared with the standard red-free photographic technique, a 560-nm short-pass cut-off filter, used with extended-range, high-resolution, extremely fine-grain film (Kodak No. 2415 Technical Pan film), considerably enhanced the ability to resolve nerve fiber bundles.
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