What happens to the eye?

Age-related macular degeneration (AMD) is a disease of ageing ocular tissues in particular the retinal pigment epithelium (RPE). The RPE provides essential metabolic support to the retina through daily phagocytosis of rod outer segments and ensuing lipid metabolism, water/molecule transport, retinoid recycling/storage, maintaining the blood-retinal barrier, detoxification, and secretion of trophic factors.

AMD is classified into either a dry, atrophic type, or wet, exudative type. In both forms of AMD, there is damage and progressive loss of sub-macular RPE cells. In the dry form, there is a slow progressive decline in visual function as the RPE layer and the overlying macula atrophy. In the wet form, stiffened Bruch’s membrane easily becomes fractured and a combination of inflammatory and angiogenic factors are released which lead to choroidal neovascular membrane (CNVM). The neovascular membrane will quickly leak fluid, cause bleeding or both, which further depletes RPE.

In both forms of AMD, loss of the supporting RPE layer results in photoreceptor death, and visual deterioration. The course of events tends to be rapid and aggressive in the wet form of AMD which accounts for 10% of cases. Unfortunately, 10-20% of dry cases eventually convert to the wet type.