Inflammation in Age-Related Macular Degeneration – Implications for Therapy

Abstract

The macula or macula lutea (originally from Latin macula, “spot” and lutea, “yellow”) is an oval-shaped spot, five mm in diameter, located temporal to the optical nerve and near the centre of the human retina. Although it comprises only a small part of the retina, it is responsible for the sharp central vision and colour vision. Age-related macular degeneration (AMD) is a disease in which the neuroretina and retinal pigment epithelia (RPE) of the macula degenerate with age resulting in profound loss of visual function. At the early stages, so called age-related maculopathy, patients present with “drusen”, the “biological waste materials” deposition, between RPE cells and the choroid especially in the macular region (Coleman et al. 2008, Jager et al. 2008). Visual acuity is normally not affected at this stage. As disease progresses to the advanced stages, patients may lose their central vision. There are two forms of advanced AMD: dry and wet. Dry-AMD also called central geographic atrophy. Apoptosis of RPE cells and subsequent death of photoreceptors in the macula underlie the pathology of dry-AMD (Coleman et al. 2008). “Wet” AMD refers to the neovascular or exudative form of the disease and is associated with rapid vision loss caused by the infiltration of abnormal blood vessels from the choroid into the subretinal space leading to haemorrhage, leakage of fluid and eventual scar tissue formation (Chopdar et al. 2003, Coleman et al. 2008). Dry-AMD is more common than wet-AMD accounting for nearly 85~90% of AMD cases; however, wet-AMD contributes to 90% of severe vision loss resulting from AMD (Chopdar et al. 2003). In addition, AMD is generally thought to progress along a continuum from atrophic or dry-AMD to neovascular (wet) AMD with approximately 1015% of all AMD patients eventually developing the wet form (Sunness et al. 1999). Occasionally, patients can also present with exudative (wet) AMD as the first manifestation of the condition without prior signs of dry-AMD.