Abstract
PurposeTo document with spectral-domain optical coherence tomography the structural stabilization of the fovea and the sealing of outer macular defects by Müller cells.MethodsA retrospective case series of 45 eyes of 34 patients is described.ResultsIn cases of a cystic disruption of the foveola as in macular telangiectasia type 2 and vitreomacular traction, the Müller cell cone provides the structural stability of the fovea. In cases of a detachment or disruption of the Müller cell cone, e.g., in foveal pseudocysts, outer lamellar holes, and degenerative and tractional lamellar holes, Müller cells of the foveal walls may provide the structural stability of the fovea by the formation of a hyperreflective external limiting membrane (ELM) which bridges the holes in the central outer nuclear layer (ONL). Müller cells of the foveal walls and parafovea mediate the regeneration of the foveal architecture in cases of outer lamellar and full-thickness macular holes. The regeneration proceeds by a centripetal displacement of photoreceptor cell somata which closes the holes in the central ONL. The closure may be supported by the formation of a glial tissue band at the ELM which seals the hole.ConclusionsThe Müller cell cone provides the foveal stability in cases of a cystic disruption of the foveola. The structural stability of the outer foveal layers is mainly provided by the Müller cells of the foveal walls and parafovea; these cells also mediate the regeneration of the outer fovea in cases of a defect of the central ONL.
Highlights
The structural stability of the fovea is provided by two populations of Muller glial cells: specialized cells which form the so-called Muller cell cone in the foveola, and Muller cells of the foveal walls and parafovea which have a characteristic z-shape because their outer processes run horizontally or obliquely through the Henle fiber layer (HFL) toward the foveal center [1,2,3,4]
The structural stability of the outer foveal layers is mainly provided by the Muller cells of the foveal walls and parafovea; these cells mediate the regeneration of the outer fovea in cases of a defect of the central outer nuclear layer (ONL)
Macular telangiectasia type 2 is characterized by a progressive bilateral cystic degeneration of the ONL in the fovea because of a loss of photoreceptor cells [22, 23]
Summary
The structural stability of the fovea is provided by two populations of Muller glial cells: specialized cells which form the so-called Muller cell cone in the foveola, and Muller cells of the foveal walls and parafovea which have a characteristic z-shape because their outer processes run horizontally or obliquely through the Henle fiber layer (HFL) toward the foveal center [1,2,3,4]. The structural stability of the outer layers of the fovea (HFL, ONL) is suggested to be mainly provided by the outer processes of the Muller cells of the foveal walls and parafovea [4]. These processes surround the fibers and somata of photoreceptor cells, and constitute, together with the photoreceptor cells, the external limiting membrane (ELM) [3, 13]. The spatial arrangement of the Muller cell processes in the central ONL and the morphology of lamellar holes without disruption of the outer retinal layers may suggest that Muller cells of the foveal walls stabilize
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