Photo-oxidation

Within the visible light spectrum (390 – 700nm), shorter wavelength photons carry more energy to the retina.  This high energy visible (blue) light results in a photo-oxidation reaction, where waste products deposited in the retina are oxidized by the high energy photons.  Found in the retinal pigment epithelium, Lipofuscin is an accumulation of undegradable products of photoreceptor outer segment metabolism.  The chromophores in Lipofuscin (e.g. A2E) are strongly excited by the high energy light, producing increased levels of damaging reactive oxygen species leading to increased oxidative stress.

Macular pigment provides protection from this process, firstly by filtering the high energy visible light before it reaches the chromophores (macular pigment filters blue light because it is yellow in color, with a peak absorption around 460nm).  Secondly, the reactive oxygen species formed are quenched by the macular pigment, due to its ability to donate electrons and protect against oxidative damage.