Stromal reflectivity is chiefly dependent on the narrow, uniform diameter of collagen I fibrils and the regularity of the spacing between these collagen fibrils, which itself is regulated by the interaction of collagen with interfibrillar proteoglycans.
20 In recent years, advanced imaging techniques have led to novel insights into the presence and role of fibrillin-1 containing microfibrils within the corneal stroma.
21 In contrast with microfibrils in the sclera, which carry an elastin core, the stroma of a normal human cornea contains a network of elastin-free, fibrillin-1-containing microfibrils, most abundant in the posterior stroma and becoming progressively less present anteriorly.
22 In
FBN 1+/− mouse corneas, significantly reduced amounts of fibrillin-1-containing microfibrils have been detected, as well as microfibril disorganization compared to controls, both at the adult and late embryonic stage.
22,23 The lens capsule in human MFS patients has similarly showed both quantitative and qualitative changes, with irregular and fragmented bundles evident upon histologic analysis.
24 In adult
FBN 1+/− mouse corneas, the interfibrillar spacing of collagen fibrils has been shown to be increased, despite the reduced corneal thickness, which indicates a lower number of collagen lamellae in the adult
FBN 1+/− corneas compared to wild-type mice.
22,23 The exact cause of the altered collagen organization in MFS remains unknown but may relate to the decreased decorin levels or the higher TGF-
β activity detected in MFS corneas.
23 The increased stromal reflectivity detected in MFS eyes in this study may reflect the altered collagen architecture and consequently, the optical properties of the stroma. In vivo confocal microscopy (IVCM) of the cornea of MFS patients have also demonstrated increased backscattering of light at the level of the stroma because of a highly reflective extracellular matrix of the stroma.
10,25