Three-dimensional arrangement of elastic fibers in the human corneal stroma

Abstract

The cornea is the main refracting lens in the eye. As part of the outer tunic it has to be resilient, a property conferred by the organisation of the constituent collagen. It also has to be sufficiently elastic to regain its exact shape when deformed, in order not to distort the retinal image. The basis of this elasticity is not fully understood. The purpose of this study was to characterise in three dimensions the arrangement and distribution of elastic fibers in the human corneal stroma, using serial block face scanning electron microscopy. We have demonstrated that there exists a complex network of elastic fibers that appear to originate in the sclera or limbus. These appear as elastic sheets in the limbus and peripheral cornea immediately above the trabecular meshwork which itself appears to extend above Descemet's membrane in the peripheral stroma. From these sheets, elastic fibers extend into the cornea; moving centrally they bifurcate and trifurcate into narrower fibers and are concentrated in the posterior stroma immediately above Descemet's membrane. We contend that elastic sheets will play an important role in the biomechanical deformation and recovery of the peripheral cornea. The network may also have practical implications for understanding the structural basis behind a number of corneal surgeries.

Elastic microfibril distribution in the cornea: Differences between normal and keratoconic stroma

“…Both staining protocols clearly demonstrated the presence of an extensive network of MBs anterior to Descemet's membrane in normal cornea, as we have previously described (Lewis et al., 2016). Many data sets were obtained from the same area, at all radial positions, from both tannic acid and orcein stained keratoconic buttons, with MBs visible in only one reconstruction.…”

“…This is a finding that was not seen in full thickness quantification analysis of normal cornea, where no elastic material was detected below the epithelium (Lewis et al., 2016). These MBs were much smaller in diameter when compared to those seen in the middle and posterior stroma; this, along with poor contrast, made it difficult to create the 3D reconstruction (Video clip S1).…”

“…An increased concentration of MBs below the epithelium/Bowman's layer in keratoconus corneas may be a wound repair response to biomechanically stabilise this weakened area to prevent rupture. If this is correct, the presence of MBs in this area, which were not observed in normal cornea (Lewis et al., 2016), may also have an effect on the shape of the cornea and could potentially contribute to cone formation.…”

Dynamics of big bubble formation in deep anterior lamellar keratoplasty by the big bubble technique: in vitro studies

“…Recently, Lewis et al. () demonstrated the existence of an annulus of an elastic fibre system in the cornea‐scleral limbus, which extends into the posterior cornea as a thin layer, maximally concentrated in the PDL. These features could all contribute to the circumferential migration of air and the relatively limited antero‐posterior ‘inflation’ of this region.…”

Small Artery Elastin Distribution and Architecture—Focus on Three Dimensional Organization

“…Hill, unpublished data), particularly as it relates to the spatial relationships between cells of the vascular wall and the surrounding ECM. Of direct relevance Lewis et al [28] have recently used "serial block face" scanning electron microscopy to examine the 3D arrangement of elastic fibers in human corneal stroma and argue that architectural patterns contribute to both biomechanical deformation and recovery. Similarly, advances are occurring in analysis routines for quantifying the structural arrangement of the ECM [1].…”