Alessia Ruffini

Age-related macular degeneration (AMD) and retinal detachment are among the leading causes of blindness in developed countries. Macular edema, which consists of intra- or sub-retinal fluid accumulation in the macular region is closely associated with AMD. This pathology occurs in numerous retinal disorders and can cause severe impairment of central vision. The symptoms include blurred or wavy central vision, difficulty in reading, and alteration of colors, highly influencing the quality of everyday life. Clinical observations show that fluid accumulation typically occurs in the fovea, although there are no blood vessels there. My Ph.D. work seeks an explanation for this observation. In literature, there is still no systematic attempt to give an interpretation with a model. Moreover, the pathogenesis of macular edema is not entirely understood.

In patients affected by exudative macular edema, a fluid accumulation occurs in correspondence with the fovea. The fovea is the center of a region of the retina called “macula,” which presents the higher numbers of photoreceptors, leading it to be the area responsible for high-resolution vision. Consequently, macular edema leads to blurred vision, distortion of central vision, and altered colors. All these symptoms can have a significant impact on everyday life. The findings of this work aim to understand the mechanisms behind this pathology, which are still not fully known. Understanding the basic principles of macular edema formation and accumulation represents a starting point for future developments in this field.

Müller cells (MC) are the critical element in this work, and their density varies along the retina. Moreover, MCs are orthogonal to the retinal surface at their extremities and inclined in the middle layer. It has been hypothesized that this reduces tissue permeability there, and this assumption is justified by a calculation based on homogenization theory. It studied fluid motion in the retina in the presence of leakage from damaged vasculature, modeling the tissue as a non-homogeneous, anisotropic, poroelastic medium. It is assumed that fluid and proteins exude from capillaries at a given distance from the axis of symmetry, owing to impairment of the blood-retinal barrier.

The model suggests that MCs' density and conformation significantly impact fluid motion in the retina during macular edema. Fluid accumulates in the foveal region since this region is more compliant than the rest of the retina, and the pressure there is higher.