INTRODUCTIONEn-face optical coherence tomography (OCT) is an emerging imaging modality that facilitates the assessment of retinal structures transversely.1,2 Available since 2006 on certain OCT devices, the first retinal transverse scans were difficult to analyze interpret as only plane sections of the concave retina were available. 3 More recently, Spectral-Domain OCT technology with advanced alignment algorithm have adjusted sections to a reference curve, which has allowed layer-by-layer retinal imaging and provided a new investigation tool for a range of retinal disorders.
4-9The foveal microstructure is formed by a dense compaction of cone photoreceptors and their projected axons, which are intertwined with retinal glial Müller cells and follow a centrifugal course towards the inner layers at the edges of the fovea. Retinal glial Müller cells are critical for retinal homeostasis, providing metabolic support to neighboring neural cells, delivering neuroactive substances and retinoids to cones, and recycling waste compounds. 10,11 Müller cells are 5 times more abundant in the macula than in the peripheral retina.12 The "Z-shape" morphology of perifoveal Müller cells has been observed on histological sections in both animal and human models, where the cells adopt three consecutive orientations (Figure 1). 13,14 From the internal limiting membrane, perifoveal Müller cells run vertically to the inner nuclear layer, then turn inwards towards the foveal center across the outer plexiform layer and the Henle's fiber layer where their course is oblique and almost horizontal in the internal portion of the foveal pit. Then, at the junction with the outer nuclear layer, they take a vertical orientation again to reach the external limiting membrane (Figure 1). At the external limiting membrane of the primate retina, Omri et al. have previously shown that Müller cells and photoreceptors are bound by tight-like junctions, where the proteins occludin and zonula occludens-1 are expressed.
15Intraretinal fluid accumulation disrupts the foveal architecture, presenting an opportunity to examine its components in better detail. In full-thickness macular hole (MH), intraretinal cysts are frequently observed on OCT around the edges of the hole. On fluorescein angiography, no vascular leakage or filling of the cysts is usually observed. 16 This suggests that they originate from a metabolic dysfunction and supports the hypothesis of Müller cells implication in the pathogenesis of fullthickness MH. [17][18][19] In this study, we use en face OCT to characterize and quantify layer by layer, the perifoveal cystic cavities occurring around full-thickness MHs. To support the OCT findings, we used human and non-human primate macular flat-mounts and sections to visualize Müller cells stained with a glial marker.
METHODS
SubjectsThis observational case series adhered to the tenets of the Declaration of Helsinki, and the need of approval was waived by the Institutional Review Board of the Nuovo Regina Margherita Hospital, due to its retrospect...