Light scattering from edematous human corneal grafts’ microstructure: experimental study and electromagnetic modelization

Abstract

Along with the lens, the cornea is the only transparent tissue in the human body. However, the development of an edema involves structural disturbances increasing light scattering and leading to the opacification of the cornea. Several mechanisms of transparency loss have been studied in the literature, but the whole phenomenon is complex and the part played by each scatterer is still unclear. We propose here to study human corneal grafts combining microscopic OCT imagery with far-field measurement of the scattered light in the reflected half-space. We introduce afterwards numerical calculations based on electromagnetic equations solved with first order approximation to link the observed microscopic-scale structural modifications with the intensity level of the scattered light, and to try and quantify the relationship between them.

Corneal structure and transparency

“…Matrix changes also occur but these contribute less to the observed light scatter. A similar effect occurs in corneal oedema (bullous keratopathy, Fuch's dystrophy) but in this case there are local decreases in refractive index caused by pooling of fluid into so-called “lakes” ( Casadessus et al., 2012 ) ( Fig. 8 ).…”

Sun protection and hydration of stratum corneum: a study by 2‐D differential method

“…We will assume throughout this study that the hydration of the SC results in a thickness increase of the corneocytes, which has already been established . A quick comparison between SC and eye cornea shows that cornea hydration increases the opacity of the cornea by increasing its thickness .…”

Birefringence analysis of collagen supraorganization in cat corneas with tropical keratopathy

“…15,16 An increase in light scattering and optical dispersion can lead to corneal opacification and impaired vision due to loss of transparency. 1,17,18 Although the causes of increased optical dispersion may vary, many studies of dystrophy-affected opaque corneas show alterations in the supraorganization of the fibrils. 17,[19][20][21][22] Moreover, Chakravarti et al 23,24 demonstrated that in mice with a null mutation in the gene encoding the proteoglycan lumican, which regulates type I collagen fibrillogenesis, congenital corneal opacities are associated with changes in fibrillar thickness and the paths of collagen fibers within the stroma.…”

“…An increase in light scattering and optical dispersion can lead to corneal opacification and impaired vision due to loss of transparency 1,17,18 . Although the causes of increased optical dispersion may vary, many studies of dystrophy‐affected opaque corneas show alterations in the supraorganization of the fibrils 17,19–22 .…”