We avoid the sun light in the peak of the days, we make sure we use natural skin care, parabens, mineral oils and titanium dioxide free. Yet we most often do not realise the negative consequences of the light from screens we tend to (or must) spent so much time in front of.

Most of the light we are exposed to comes from the sun, that one is welcome and needed, but we also receive blue light every day through LED screens; telephones, computers, TV. On average, we spend a third of the day in front of these devices.

In the visible spectrum, high energy short wave (between 415 and 455 nm) blue light is the most harmful and can cause eye damage. Direct penetration into the retina causes irreversible photochemical retinal damage. This light passes through the cornea and lens to the retina causing diseases such as dry eye, cataract, age-related macular degeneration, photochemical injury to the retina – photoretinitis, also stimulating the brain, inhibiting melatonin secretion and enhancing adrenocortical hormone production, which destroys the hormonal balance and directly affects sleep quality.

Because of blue light’s short wavelength, the focus is not located in the center of the retina, but in front of it, thus long exposure to blue light causes a worsening of visual fatigue and nearsightedness.

Effects of blue light on cornea

The cornea covers the front end of the eyeball and is the first structure the light encounters when passing through the eye. Blue light from artificial sources can trigger inflammation of human corneal epithelial cells. Thus, oxidative damage and apoptosis lead to further ocular inflammation. Blue light also causes dry eye; the microvilli of the corneal epithelium lose the support and stability of the tear film, leading to the formation dry eyes.

On the other hand, blue light irradiation is used as a treatment for bacterial keratitis. The 440 nm wavelength combined with riboflavin for bacterial keratitis demonstrates that blue light can effectively control the corneal ulcer caused by a Staphylococcus aureus infection.

Effects of blue light on lens

The lens is the main optical power and also effectively filters short light waves to reduce retinal light damage, because it contains structural proteins, enzymes and protein metabolites that absorb short wave light. These substances and derivatives are added to the lens’s protein to produce yellow pigments, causing the lens to gradually darken and turn yellow – cataracts. In the eye, carotenoid lutein and zeaxanthin are effective antioxidants and are the only carotenoids in the lens. They absorb short-wave blue light. Having antioxidants in your diet enables protection of the antioxidant defense systems from oxidative stress. Because once oxidative stress occurs, the redox state of these antioxidants can be improved, providing protection for the lens.

Effects of blue light on retina

Retina is the initial site of vision formation. Blue light penetrates through lens to the retina and can cause retinal photochemical damage. It stimulates local oxidative stress in cells of the retinal pigment epithelium. Mitochondria are the main targets of oxygen free radicals. Under aerobic conditions, blue light induces a large number of free radicals, destroys messenger ribonucleic acid (mRNA) and proteins, causes necrosis of photoreceptor cells and pigment epithelial cells. The radiation spreads rapidly and the Ca²⁺ signal transmits to adjacent cells, which induces changes in the mitochondrial membrane potential. The high baseline Ca²⁺ levels lead to localised cell damage in the retinal pigment epithelial cells. More studies on blue light’s effects on the retina need to be conducted.

Eyesight

Screen time can lead to poor eyesight and higher numbers of nearsightedness. Natural light is more concentrated in short-wave blue light than artificial light sources, which reduces the eye length through the mechanism of retinal dopamine release.

Sleep quality

Natural blue light regulates the body clock and promotes alertness, memory and cognition. It stimulates the secretion of melatonin in pineal gland which can increase or decrease cortisol expression depending on time of day, regulating human circadian rhythm. If blue light is excessive, especially artificial at night when melatonin production peaks, it can not only damage the retina through the ocular surface, it can also inhibit melatonin secretion, directly affecting sleep quality.

How it affects our skin

Our body has mechanisms that protect us from blue light, specific proteins are activated as soon as our eyes detect blue light of wavelenghts between 415 and 455 nm. The proteins are in the cells of the retina and secreted from the epidermis and trigger the renewal of skin cells. Blue light is harmless in natural and small doses, but after several hours in front of a screen, we exceed the normal amount of exposure. Blue light penetrates into the dermis, causing oxidative stress and premature aging. It is also responsible for the release of free radicals, which cause the breakdown of natural collagen in the skin. Screen time therefore brings with it photoaging, hyperpigmentation and loss of skin elasticity. If we add to this the lack of sleep, which is directly related to artficial blue light exposure, we are subject to these changes even more.

Prevention

Working and living conditions and people’s life styles are changing, with it more exposure to artificial blue light is occurring. The prevention and control of the damage is becoming more important and anti-blue light products are emerging. Mainly affected by blue light are our skin and eyes. The skin care industry has launched some products that supposedly protect from blue light. They recommend products containing vitamin A or retinol. They stimulate the skin’s natural renewal process, reducing the development of fine lines and dark spots. Products that contain UVA and UVB protection factors are also often a part of the care. There are also screen or blue light glasses available or, if you wear dioptre glasses, this fileter can be added to the order.

A certain degree of natural blue light can improve eye health, slow the growth of eye axis, prevent myopia and it regulates circadian rhythms. Normal digital displays present minimal risks, but only at short-term exposure (not hours every day). It is necessary that we take anti-screen measures after longer exposure. We should minimize the use of electronic devices and avoid blue light at night, to ensure good sleep and eye closure time. The anti-blue light glasses or screen cover may be a good choice to avoid injury.

In summary, a certain extent of natural blue light is necessary to regulate circadian rhythm, but there are many harmful effects on human eyes. Blue light can produce different degrees of damage to cornea, lens and retina. We must protect ourselves when using products that emit blue light, especially at night. It’s hard to give up technology completely on a daily basis, as we mostly need it for work, but we can reduce the impact of screens with a little effort. There are filters that block blue light in settings on all or most of our devices. How about just taking screen-free afternoons and evenings?

Sources:

• Okuno T. Evaluation of blue-light hazards from various light sources. 2002
• Zhao Z.-C.,  Zhou Y., Tan G., Li J. Research progress about the effect and prevention of blue light on eyes. 2018

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