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Schierz, C. IS LIGHT WITH LACK OF RED SPECTRAL COMPONENTS A RISK FACTOR FOR AGE-RELATED... With increasing age a nearly linear increase of lipofuscin in the form of granules can be observed (Figure2). For this reason it is also called “ageing pigment”. By 80 years of age lipofuscin can occupy up to 19% of the RPE cell volume (Pawlak et al., 2002). In addition to age, the main risk factors for AMD are believed to be smoking, genetic predisposition and having high blood pressure. Figure 2 – Age-related accumulation of lipofuscin in the retinal pigment epithelial cells (RPE- cells) in the fovea (left) and 7° temporal to the fovea (right) by means of fundus fluorescence measurements. F.U. are relative fluorescence units corrected for lens absorption. Adapted from Delori, Goger, and Dorey (2001, Fig. 2). 2 Impact of blue spectral light components on AMD Photochemically induced blue light hazard (BLH) destroys retinal photo receptors with relatively short exposure times. In contrast, in the longer term, chemical mechanism modified as a result of cumulative light effects may contribute to age-related macular degeneration (AMD) (Wu, Seregard, and Algvere, 2006). An epidemiologic study concludes that exposure to sunlight may be associated with the development of early AMD: Time spent outdoors while persons were aged 13 to 39 was significantly associated with this risk (Cruickshanks et al., 2001). Since lipofuscin and in particular its component A2E acts as photosensitizer it is potentially harmful. By means of light with increased blue spectral components it can generate free radicals inside the RPE-cells (Sparrow, Nakanishi, and Parish, 2000). Free radicals are aggressive oxygen molecules like hydrogen peroxide (H2O2), singlet oxygen (+O2) or superoxide (O2‒). Free radicals are highly chemically reactive with their unpaired electron and are responsible for the formation of oxidative stress, which is considered to be destructive for RPE-cells and can lead to AMD. In addition, this process is leading to an increased loss of rods and cones, since RPE-cells are responsible for the regeneration of these photoreceptors as well as for the restoration of the associated photo-pigments by means of the “visual cycle” (Lamb and Pugh, 2004). The biomolecule A2E as part of lipofuscin is a degradation product of the rods. Apart from its toxic effects, A2E prevents the lysosomes from removing decomposition products which in turn promotes the formation of drusen (Finnemann, Leung, and Rodriguez-Boulan, 2002). As a result of the age dependent increase of lipofuscin, the risk for damage caused by short-wave light also increases with age. The yellowing of the eye lens with increasing age (van de Kraats, and van Norren, 2007; CIE, 2012) can counteract this process to a certain extent. Arnault et al. (2013) could demonstrate that light with wavelengths between 415nm and 455 nm could lead to changes within the RPE-cells if the concentration of A2E is increased. It is possible that other components of lipofuscin with other action spectra in the same spectral range (<455nm, blue-violet) are involved (Pawlak et al., 2002). In a clinical trial a certain Proceedings of 29th CIE Session 2019 115PDF Image | LIGHT WITH LACK OF RED SPECTRAL COMPONENTS v amd
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