What is AMD
Age-Related Macula Degeneration (AMD) is a major cause of blindness in elderly people in industrialised countries. You can distinguish the atrophic (“dry”) and the exudative (“wet”) form, which is the more devastating one. Both are promoted by various environmental risk factors as well as genetic factors. The exudative form of AMD is characterised by the ingrowth of vessels into the central part of the retina that normally is free of blood vessels (“choroidal neovascularisation, CNV”). This CNV is triggered by an imbalance of angiogenic (vessel growth promoting) and anti-angiogenic (vessel growth inhibiting) factors in favour of vessel growth. Most prominent molecules are the angiogenic vascular endothelial growth factor (VEGF) and the anti-angiogenic protein pigment epithelium-derived factor (PEDF). All these devastating processes are focused on the macula, the place for central and sharp vision in the human retina.
The pathology of AMD probably starts with an impairment of the RPE (retinal pigment epithelium) cell layer. The reasons for this loss of function are not completely understood. Inflammation, cellular stress and genetic predisposition are possible causes for the degeneration that, untreated, leads to blindness. The RPE cells are no longer able to preserve a functional retina by sustaining the visual cells, supporting them with essential nutrients, regenerating the light-sensitive molecule opsin and disposing of waste products.
In dry AMD, waste products accumulate in and around the RPE cells forming so-called drusen that damage the RPE cells, which finally die. Consequently, the RPE cells can no longer preserve the visual cells, which will degenerate next. In exudative AMD, Bruch’s membrane, a barrier of the outer retina, will become permeable and vessels from the will penetrate the retina. Additionally, a perturbed cellular metabolism leads to an imbalance of angiogenic and anti-angiogenic factors, promoting vessel growth in the retina, which untreated leads to retinal degeneration and blindness.