The Henle Fiber Layer in Albinism: Comparison to Normal and Relationship to Outer Nuclear Layer Thickness and Foveal Cone Density

Abstract

PurposeDirectional optical coherence tomography (D-OCT) allows the visualization of the Henle fiber layer (HFL) in vivo. Here, we used D-OCT to characterize the HFL and outer nuclear layer (ONL) in albinism and examine the relationship between true foveal ONL and peak cone density.MethodsHorizontal D-OCT B-scans were acquired, registered, and averaged for 12 subjects with oculocutaneous albinism and 26 control subjects. Averaged images were manually segmented to extract HFL and ONL thickness. Adaptive optics scanning light ophthalmoscopy was used to acquire images of the foveal cone mosaic in 10 subjects with albinism, from which peak cone density was assessed.ResultsAcross the foveal region, the HFL topography was different between subjects with albinism and normal controls. In particular, foveal HFL thickness was thicker in albinism than in normal controls (P < 0.0001), whereas foveal ONL thickness was thinner in albinism than in normal controls (P < 0.0001). The total HFL and ONL thickness was not significantly different between albinism and controls (P = 0.3169). Foveal ONL thickness was positively correlated with peak cone density in subjects with albinism (r = 0.8061, P = 0.0072).ConclusionsFoveal HFL and ONL topography are significantly altered in albinism relative to normal controls. Our data suggest that increased foveal cone packing drives the formation of Henle fibers, more so than the lateral displacement of inner retinal neurons (which is reduced in albinism). The ability to quantify foveal ONL and HFL may help further stratify grading schemes used to assess foveal hypoplasia.

Adaptive Optics Retinal Imaging inCNGA3-Associated Achromatopsia: Retinal Characterization, Interocular Symmetry, and Intrafamilial Variability

“…The residual Henle fiber layer (HFL) may have been included within the ONL measurement, but given the foveal location, only a small degree of error is expected. The HFL comprised only 17.5% of the measured HFL+ONL thickness (range, 11.4%–24.8%) at the fovea of healthy controls 47. Due to a small number of subjects with grade 1 and 3 EZ, the data were not further statistically analyzed.…”

Assessing Ganglion Cell Layer Topography in Human Albinism Using Optical Coherence Tomography

“… 17 , 60 Moreover, the range of foveal structural specialization observed in albinism overlaps with the normal population. 10 , 61 , 62 In the future, continuous metrics of foveal structure may be better equipped to capture the diversity in foveal structure within and between different retinal pathologies and provide greater insight into structure–function relationships in foveal hypoplasia. It is encouraging that some studies have already begun to use continuous metrics to evaluate foveal hypoplasia severity, 14 , 63 and we believe that GCL and IPL topography will provide yet another tool to accomplish this goal.…”

Retinal Layer Thicknesses in Early Age-Related Macular Degeneration: Results From the German AugUR Study

“…For example, it does not support the segmentation of the Henle's fiber layer (HFL), that is the axons of photoreceptor nuclei. Moreover, a particular SD-OCT imaging method is required to distinguish HFL from true ONL by altering the beam entry position (also termed directional OCT)55,56; we did not apply this technique; therefore, HFL is not readily visible on AugUR images and, consequently, we refrained from trying to manually delineate HFL, which would have been too error-prone. We acknowledge that the recognition of the optical properties of HFL could help gain a more thorough understanding of the retina in health and macular pathology 55,56…”