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B. J. Lujan, A. Roorda, R. W. Knighton, J. L. Duncan, J. Carroll; Henle's Fiber Layer Revealed Using Spectral Domain Optical Coherence Tomography. Invest. Ophthalmol. Vis. Sci. 2010;51(13):1201.
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© ARVO (1962-2015); The Authors (2016-present)
The axons of foveal photoreceptors form Henle’s fiber layer (HFL). These cylindrical structures are oriented obliquely between photoreceptor nuclei and bipolar cell dendrites. The retinal nerve fiber layer (NFL), also comprised of cylinders, exhibits directional reflectance properties and is readily seen in spectral domain optical coherence tomography (SDOCT) images, whereas HFL has not been similarly visualized. We demonstrate a method that reliably identifies HFL in normal subjects.
Three commercial SDOCT systems from different manufacturers were used to image subjects with normal appearing maculas. Frame averaged B-scans were obtained through the fovea via multiple pupil entry angles. Using pupil camera images from one SDOCT system in conjunction with biometric data, the effect of entry position on HFL reflectance was modeled.
A directionally reflective signal from the inner aspect of the outer nuclear layer (ONL) was identified as HFL by its anatomic location. Standard SDOCT acquisition through the optical axis typically showed no clear partition between the ONL and HFL. With an eccentric pupil entry position, however, HFL contralateral to the fovea became markedly hyperreflective relative to the underlying ONL. Ipsilateral to the fovea, HFL was hyporeflective relative both to the ONL and the overlying outer plexiform layer, clearly delineating these optical borders. Reflectance from HFL was maximal when imaging at angles approaching an orientation perpendicular to its cylindrical axons.
Henle’s fiber layer is directionally reflective and can be visualized with SDOCT by altering the position of light entering through the pupil. This technique allows for true measurements of the distinct retinal layers containing photoreceptor nuclei and axons.
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