Abstract
PurposeTo conduct high-resolution imaging of the retinal nerve fiber layer (RNFL) in normal eyes using adaptive optics scanning laser ophthalmoscopy (AO-SLO).MethodsAO-SLO images were obtained in 20 normal eyes at multiple locations in the posterior polar area and a circular path with a 3–4-mm diameter around the optic disc. For each eye, images focused on the RNFL were recorded and a montage of AO-SLO images was created.ResultsAO-SLO images for all eyes showed many hyperreflective bundles in the RNFL. Hyperreflective bundles above or below the fovea were seen in an arch from the temporal periphery on either side of a horizontal dividing line to the optic disc. The dark lines among the hyperreflective bundles were narrower around the optic disc compared with those in the temporal raphe. The hyperreflective bundles corresponded with the direction of the striations on SLO red-free images. The resolution and contrast of the bundles were much higher in AO-SLO images than in red-free fundus photography or SLO red-free images. The mean hyperreflective bundle width around the optic disc had a double-humped shape; the bundles at the temporal and nasal sides of the optic disc were narrower than those above and below the optic disc (P<0.001). RNFL thickness obtained by optical coherence tomography correlated with the hyperreflective bundle widths on AO-SLO (P<0.001)ConclusionsAO-SLO revealed hyperreflective bundles and dark lines in the RNFL, believed to be retinal nerve fiber bundles and Müller cell septa. The widths of the nerve fiber bundles appear to be proportional to the RNFL thickness at equivalent distances from the optic disc.
Highlights
The sensory retina is composed of nine contiguous layers, linked to each other by synaptic connections
Red-free fundus photography is the standard approach for examining the retinal nerve fiber layer (RNFL), changes in the RNFL are often not detectable until there is more than 50% nerve fiber loss [1]
The hyperreflective bundles above and below the fovea appeared from the temporal periphery on either side of a horizontal dividing line to the optic disc in an arched shape
Summary
The sensory retina is composed of nine contiguous layers, linked to each other by synaptic connections. Evaluation of the retinal nerve fiber layer (RNFL) is crucial for detecting and managing glaucoma, which is a progressive optic nerve disease characterized by a loss of the RNFL. Red-free fundus photography is the standard approach for examining the RNFL, changes in the RNFL are often not detectable until there is more than 50% nerve fiber loss [1]. Another limitation is the difficulty in obtaining fundus photographs with sufficient quality for interpretation, especially in eyes with a hypopigmented fundus or myopia, when background reflection is high and contrast is low. Studies using commercially available OCT have not, provided sufficiently clear images of individual nerve fiber bundles to identify a specific structural abnormality that underlies the pathogenesis of glaucoma
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