Today, many professional optical magazines are actively discussing the effect of the blue range of visible radiation on human health. Many manufacturers of vision correction products have released new types of optical coatings for eyeglass lenses that reduce the transmission of blue light. What is the reason for such close attention to this form of radiation that is customary for humans and what special products are presented on the optical market? The proposed article is intended to answer these questions.
What is blue light?
From the point of view of physics, light is one of the types of electromagnetic radiation emitted by luminous bodies, as well as resulting from a series of chemical reactions. Electromagnetic radiation has a wave nature – it propagates in space in the form of periodic oscillations (waves) made with a certain amplitude and frequency.
The human eye is able to perceive electromagnetic radiation only in a narrow range of wavelengths – from 380 to 760 nm, called visible light; the maximum sensitivity falls on the middle of the range — about 555.
|Properties of the fundamental spectral colors of visible radiation|
|Colour||Range of wavelengths, nm||Frequency Range, THz||Range of photon energy, eV|
The effect of blue light on the human body
For several decades, scientists have carefully studied the effect of blue light on the human body and found that its long-term effect affects the health of the eyes and circadian rhythms, and also provokes a number of serious diseases.
- Effect on the eyes. In many studies, it was noted that exposure to blue light leads to the formation of photochemical damage to the retina, especially its pigmented epithelium and photoreceptors, and the risk of damage increases exponentially with increasing photon energy. According to research results, under equal experimental conditions, blue light is 15 times more dangerous for the retina than the entire remaining range of the visible spectrum (Fig. 3-8) It has also been proven that tissue changes after prolonged exposure to bright blue light are similar to those associated with symptoms of age-related macular degeneration (VDM). In 2004, the United States published the results of the study, The Beaver Dam Study, which involved 6 thousand people, and observations were carried out over 5-10 years. It was pointed out that the cumulative effect of sunlight is associated with a risk of VDM, and a relationship has been established between VDM and exposure to blue eyes. Blue light causes a photochemical reaction that produces free radicals that have a damaging effect on photoreceptors – cones and rods. The metabolic products formed as a result of the photochemical reaction cannot be properly utilized by the retinal epithelium, they accumulate and cause its degeneration.
- The International Standards Organization (ISO) in the ISO 13666 standard named the wavelength range of blue light centered at 440 nm the range of functional risk for the retina. It is these blue light wavelengths that lead to chorioretinopathy and VDM. Until a person reaches middle age, blue light is not absorbed by such natural physiological filters as the tear film, cornea, lens and vitreous body of the eye. The highest permeability of the short-wavelength visible blue light is found at a young age and slowly shifts to the longer-wavelength visible range as the human lifespan increases. The eyes of a 10-year-old child can absorb 10 times more blue light than the eyes of a 95-year-old man.
- Thus, the risk group includes three categories of the population: children; people with increased photosensitivity, working in conditions with bright lighting with energy-saving fluorescent lamps; patients with intraocular lenses (IOL). The greatest risk of damage to the retina as a result of prolonged exposure to blue light is in children whose lens does not protect against short-wave visible radiation and who spend a lot of time on electronic digital devices. Adults are better protected since their lens is less transparent and able to absorb some harmful blue light. However, for patients with implanted IOLs, the risk of damage is greater, since these lenses do not absorb blue light, although most of them absorb ultraviolet radiation.
- Effect on circadian rhythms. Circadian rhythms (from lat. Circa – around, around and lat. Dies – day) are cyclical fluctuations in the intensity of various biological processes associated with the change of day and night, or the so-called internal clock of the body.
Over the course of a long evolution, man, like all life on Earth, has adapted to the daily change of dark and daylight hours. One of the most effective external signals that support the 24-hour life cycle of a person is light. Our visual receptors send a signal to the pineal gland; it determines the synthesis and releases into the bloodstream of the neurohormone melatonin that causes sleep [URL: http://ru.wikipedia.org/ (accessed: 02.16.2014)].
When it gets dark, the production of melatonin increases and the person wants to sleep. Bright lighting inhibits the synthesis of melatonin, the desire to fall asleep disappears. Melatonin production is most strongly suppressed by radiation with a wavelength of 450–480 nm, that is, blue light.
American researchers from Harvard studied the relationship between circadian rhythm disturbances with diabetes and obesity. They conducted an experiment among 10 participants who, with the help of light, constantly shifted the timing of their circadian rhythm. As a result, it was found that the level of sugar in the blood increased significantly, causing a pre-diabetes state, and the level of the hormone leptin, which is responsible for the feeling of satiety after eating, on the contrary, decreased, that is, a person experienced a feeling of hunger even when the body was biologically saturated.
How to minimize the effects of exposure to blue light?
Today, the effects of influencing the eye’s health by such factors as ultraviolet (UV) radiation, the duration of computer work and the use of electronic devices, the tension, and type of visual load are known. Many people already understand well that it is necessary to protect not only the skin, but also eyes from UV radiation. However, the potentially dangerous effects of exposure to blue light are much less known to the general public.
What can be recommended to minimize the harmful effects of blue light?
- First of all, you should try to avoid the use at night of electronic devices such as tablet computers, smartphones and any other gadgets with luminous liquid crystal displays. If this is nevertheless necessary, Blue light blocking glasses with lenses that block blue light should be worn.
It is not recommended to look at the displays of electronic devices for 2-3 hours before going to bed. In addition, it is impossible to install fluorescent and LED lamps with excess radiation in the blue region of the spectrum in rooms in which a person can be at night. Patients with macular dystrophy should generally refuse to use such lamps.
- Children must be outdoors in the daytime for at least 2-3 hours. Exposure to the blue component of natural solar radiation helps restore the correct regime of falling asleep and waking up. In addition, outdoor games involve visual activity at a distance greater than the length of the arm, which provides relaxation and rest of the eye accommodation system.
- Children should be encouraged to use glasses with lenses that selectively transmit blue light when using electronic devices at school and at home.
During the day, during daylight hours, everyone needs to be outdoors for as long as possible – this helps to improve falling asleep and the quality of sleep at night, as well as liveliness and clarity of mind and improving mood during the day. Patients with IOL must necessarily recommend spectacle lenses that reduce the transmission of blue light to the eyes.