MaCular degeneration in the elderly is the leading cause of- blindness in the industrialized ·world today. In this report we weigh the arguments whether the dose of light, or more general, visible and invisible radiation, received during a lifetime is a factor in the pathogenesis of Age-Related Macular Degeneration (AMD). An important ground for a relation between light and AMD is the analogy with acute light damage at the cellular level, visible shortly after exposure to intense light. A relation between AMD and the so-called Ham type of acute damage is not very probable, because this type of damage only occurs in extreme conditions. Sub-threshold damage of the Noell type is a more likely candidate. In that case, the action spectrum is similar to the absorption spectrum of the visual pigments. A recent epidemiological study found an association between AMD and dose of visible light, but not with dose of UV-A and UV-B. It has been suggested that cataract would protect against AMD, but the argument is weak because the diagnosis of AMD is difficult in case of cataracts. A stronger point is found in the negative correlation between degree of ocular pigmentation and AMD. Ocular pigmentation protects the retina against light. As an explanation for the high concentration of lipofuscin (an undegradable by-product of light damage) in the macula, it has been suggested that blue light is somewhat more intense in that area than elsewhere on the retina. An alternative explanation might be found in the relatively low concentration of melanin in the pigment epithelium. Taking all arguments into consideration, we conclude that chances are high that light is indeed a factor in the genesis of AMD, but this factor is not strong. With regard to the action spectrum, it is more likely tbat it equals the absorption spectrum of the visual pigments, than that it peaks somewhere in the short wavelength region. We advise to always protect the eyes against high light levels. (Author/publisher)
Samenvatting