The fovea externa is visible on histological sections and spectral-domain optical coherence tomography (SD-OCT) images at the inwardly inclined courses of the external limiting membrane (ELM) and ellipsoid zone (EZ) lines in the foveola. ![]() Horizontally or obliquely arranged Henle fibers compensate the spatial shift between the inner and outer retinal layers. The fovea develops by a centrifugal displacement of the inner retinal layers, which results in the formation of the foveal pit (fovea interna), and a centripetal displacement of the outer retinal layers which causes a thickening of the central outer nuclear layer (ONL) and the formation of the fovea externa that is the cone-like arrangement of the thin elongated photoreceptor segments in the foveola. The foveal region is characterized by the foveal pit, the presence of avascular and rod-free zones, a high density of cone photoreceptors, and elongation of the photoreceptor outer segments (POS). The fovea as the retinal region specialized for high-acuity color vision comprises the foveola ("little fovea") and the surrounding sloping foveal walls. Spectral-domain optical coherence tomography Optical coherence tomographic angiography ONL, This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.ĭata Availability: All relevant data are within the paper and its Supporting Information files.įunding: This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.Ĭompeting interests: The authors have declared that no competing interests exist. Received: NovemAccepted: MaPublished: April 13, 2022Ĭopyright: © 2022 Bringmann et al. ![]() ![]() Badea, Transilvania University of Brasov: Universitatea Transilvania din Brasov, ROMANIA OCT angiography images recorded at the level of the HFL of eyes with high-grade foveal hypoplasia showed concentric rings of different reflectivity around the macular center such rings were not observed on images of eyes with low-grade foveal hypoplasia and control eyes.Ĭitation: Bringmann A, Barth T, Ziemssen F (2022) Morphology of foveal hypoplasia: Hyporeflective zones in the Henle fiber layer of eyes with high-grade foveal hypoplasia. Hyporeflective zones in the HFL were observed on SD-OCT images of eyes with high-grade foveal hypoplasia, but not of eyes with low-grade foveal hypoplasia and control eyes. The paracentral ONL was thickest in eyes with high-grade foveal hypoplasia and thinnest in control eyes. ![]() In contrast to central POS, the length of paracentral POS (0.5 and 1.0 mm nasal from the macular center) was not different between the three eye populations investigated. Visual acuity of subjects with foveal hypoplasia was negatively correlated to the thickness of the central inner retinal layers and positively correlated to the length of central POS. There was a negative correlation between the thicknesses of the central ONL and HFL in eyes with foveal hypoplasia however, the total thickness of both ONL and HFL was similar in all eye populations investigated. Eyes with high-grade foveal hypoplasia also displayed a thinner central outer nuclear layer (ONL) compared to eyes with low-grade foveal hypoplasia and control eyes. Eyes with foveal hypoplasia displayed shorter central photoreceptor outer segments (POS), a thinner central myoid zone, and a thicker central HFL compared to control eyes.
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