## 1 Introduction  
Wavelengths between 380 and 700 nm make the portion of the electromagnetic spectrum that is perceived by the human eye. The energy of electromagnetic radiations, including visible light, is a function of its wavelength, so shorter wavelengths are most energetic. The highest-energy portion of the visible spectrum is comprised between 380 and 500 nm, corresponding to blue-violet light [1]. The major source of blue-violet light (25-30%) is represented by sunlight. However, besides this natural source, emission peaks in the blue-violet light range may also come from artificial devices such as LED screens [2]. Many of us, in fact, are exposed every day to different sources of artificial lighting, such as white LED lamps, or LEDs used in flat screens of TVs, computer monitors, tablets and smartphones. These LED lamps are able to produce white light in three ways: (1) through the coupling of a diode with a phosphor, each emitting high- or low-frequency waves; (2) through the coupling of a diode that emits in the UV field with one or more phosphors; and (3) using several diodes that emit at different frequencies in the visible range [3]. These artificial light sources decay over time, mainly through a bleaching of phosphor, which is no longer able to absorb blue light, so that the emission of blue light increases over time [4]. We know today that ocular tissues are susceptible to damage from blue-violet light, both in the back and in the front of the eye. Exposure of mice to common LEDs or blue light caused a significant increase in ROS production, the activation of inflammatory cytokines, and ultimately the death of photoreceptors in the retina. [5; 6]. Although blue-violet light plays an essential role in color vision, excessive exposure to these wavelengths can have harmful effects due to the excessive production of ROS, which tend to damage photoreceptor cells and cells of the retinal pigmented epithelium (RPE) [7; 8; 9; 10]. So far, the role of blue-violet light on the ocular surface has been the subject of few investigations. What is known is that the generation of ROS stimulated by blue-violet light can cause inflammation of the cornea and the apoptosis of corneal cells, ultimately leading to the development or aggravation of ocular surface dysfunctions, such as dry eye [11; 12]. Lutein and astaxanthin are carotenoids belonging to the xanthophylls class, containing oxygen and being less hydrophobic with respect to carotenes [13]. Lutein, together with its stereoisomer zeaxanthin, is the only carotenoid present in the human retina [14], with the highest amount concentrated in the macula, where lutein dominates in the periphery, while zeaxanthin and meso-zeaxanthin become predominant in the center [15; 16]. Astaxanthin is a red-colored metabolite of zeaxanthin and/or canthaxanthin, containing both hydroxyl and ketone functional groups. It is very common in marine organisms feeding on phytoplankton and microalgae, such as in salmonids, shrimps and lobsters, which thus acquire a pinkish-red color [17]. It is present in the retina of fishes, amphibians, reptiles and birds in oil droplets positioned in the photoreceptor inner segment, in front and apart from the outer segment where visual pigments are concentrated [18]. In comparison to other carotenoids, such as \(\alpha\)- and \(\beta\)-carotene, lycopene and lutein, astaxanthin has shown a higher antioxidant activity in vitro [19]. Antioxidant carotenoids must be taken through the diet because they cannot be synthesized by higher organisms [20]. However, very often the amount of dietary carotenoids appears to be not sufficient for a good protection of eye structures, and several studies have pointed at the advantage of dietetic supplements to increase the concentration of carotenoids in the eye [21; 22; 23]. Dietary carotenoids mainly accumulate in the macular pigment of the retina, but they can be found also in other organs, including the skin [24].