Abstract
Purpose: :
Despite advances in SD-OCT hardware and software, Henle’s fiber layer (HFL) physiological visualization remains elusive, likely because of the inability to distinguish a change in reflectivity at the interface between the HFL and the outer nuclear layer (ONL). The aim of this study is to describe HFL appearance in different pathologies.
Methods: :
Observational case series. 47 patients with different pathologies underwent SD-OCT examination with a 6-mm line horizontal scan. 9 patients (19.1%) had central serous choriorethinopathy (CSC), 15 (31.9%) had macular edema, 2 (4.2%) presented with a macular star secondary to neuroretinitis, and 21 (44.7%) had drusen in dry age-related macular degeneration. The scans were performed with the beam centered in the pupil; the measurement beam was then tilted nasally or temporally so that the incident angle of the measurement beam was perpendicular to the HFL.
Results: :
Hyperreflectivity could be imaged in the ONL and OPL in areas of a detached neurosensory retina using SD-OCT in patients with acute central serous chorioretinopathy and that hyperreflectivity represents retinal maladjustment. In CSC, macular elevation resulting from subretinal fluid causes the detached retina to tilt toward the fovea, which results in strong backscattering from HFL. In patients with macular edema, OCT imaging has suggested that there is less retinal swelling in HFL than in the enlarged ONL with low reflectivity.The HFL thickness can increase greatly with fluid accumulation and early microcystic changes. Moreover, Henle’s fibers were found to be ‘‘standing up’’ to allow for this swelling. Backscattering is thus likely to decrease not only because of fluid accumulation in the HFL but also because of changes in the running direction of Henle fibers. In patients with macular star formation in neuroretinitis HFL is oriented radially about the fovea and is indirectly visible ophthalmoscopically and directly by SD-OCT examination. Diffuse hyperreflectivity accompanying drusen has been commented on previously and the anatomic location of hyperreflectivity attributed to drusen corresponds to HFL, and its intensity can be seen to vary substantially with pupil entry position, due to an optical effect.
Conclusions: :
Reflectivity changes are caused by alterations in the normal geometry of the retina, where pigment epithelial detachment, drusen, or subretinal fluid alters the angle of the cone of light reflecting from HFL. Optical changes in HFL are introduced by these protuberances by elevating and changing the orientation of its fibers relative to the pupil such that different segments of HFL may appear to be hyporeflective and hyperreflective overlying a single deformation.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • retina