The majority of ocular media and tissues are lifelong exposed to electromagnetic radiations. O series of photochemical and photobiological events take place in these tissues and especially in the lens and the retina, thus resulting a permanent changing of their optical and functional qualities; the result of most of these events is the appearance of fluorescent molecular aggregates due to the alterations of initially non-fluorescent molecules or to accumulation processes (these are the endogenous fluorophores; their quantity and intraocular distribution is age- and light-exposure-linked and can be altered by pathology). Willingly or not, fluorescent substances can be introduced in the eye through its hematic barriers (these are the exogenous fluorophores).