It’s easy to take for granted our access to artificial light. There’s rarely a need to keep a fire stoked or light a candle to see through darkness. We can just flip a switch to illuminate a room, reach into our pocket for our flashlight enabled phones – or heck, just read directly from our miniature computer screens. The thing is, there may be a dark side to basking in all this artificial light – particularly our exposure to blue light.
What is Blue Light?
The visible light spectrum is an actual rainbow of colors – red, orange, yellow, green, blue, indigo and violet all combine to make white light – the light we see from the sun. Each color in the visible light spectrum has a different wavelength and energy level. Visible light waves vary in length from 380 nanometers (violet light) to 700 nanometers (red light). The longer the wave, the less energy it transmits. Rays on the red end of the spectrum have longer wavelengths and less energy. On the other end, blue rays have shorter wavelengths and more energy. Blue light is the closest to invisible, ultraviolet (UV) light on the color spectrum.
Natural blue light from the sun is important for maintaining our health. Exposure to blue light during the day helps regulate our natural sleep/wake cycle, it also helps to boost mood, alertness, memory and cognitive function. But the proliferation of electronic screens and energy-efficient lighting is increasing our exposure to blue wavelengths. Blue light is emitted from a multitude of sources including sunlight, energy efficient lighting like compact fluorescent and LED bulbs, and then all the digital devices in our lives – computer screens, laptops, smartphones and TV screens.
Blue light from electronics is linked to problems with blurry vision, eyestrain, dry eye, macular degeneration and cataracts.
Let’s take a closer look.
The Dark Side of Digital Life
The cornea lies at the front end of the eyeball and is the first structure that light encounters when passing through the eye. Studies have shown the survival rate of corneal epithelial cells (the outermost layer of the cornea) when exposed to blue rays decreases, while the production of reactive oxygen species (ROS) in the same cells increases.[1] More and more evidence implicates high ROS levels with the development of glaucoma[2] and age-related macular degeneration.[3]
Moving deeper into the eye, the lens helps to filter short light waves in an effort to reduce retinal damage from UV light. It contains structural proteins, enzymes and protein metabolites that absorb short wave light, essentially creating yellow pigments (chromophores) to aid blue light absorption and also protect against potential light damage to the retina. However, as it exerts its protective effects on the retina, the lens has to undergo a decrease in transparency which can lead to cataract formation. Studies have shown that blue light can induce the production of ROS in the mitochondria of lens epithelial cells which may also lead to the development of cataracts[4].
Blue light with its short wavelengths and high energy can also penetrate even deeper into the eye. It has the potential to damage the retina (the inner lining of the back of the eye) through photochemical and photo-oxidative reactions in the retinal pigment layer. The mechanisms by which blue light damages the eye are multifactorial but primarily mediated through these light-induced oxidative stress reactions and the generation of ROS accumulation.
Short-term exposure of blue light manifests as eye fatigue, eye strain and headaches, where long-term exposure may lead to gradual loss of visual function.
How Blue Light Affects Sleep/Wake Cycles
Not only does excess exposure to blue light compromise the structural integrity of the eye but it can also affect sleep quality by supressing melatonin production. Darkness prompts the pineal gland to start producing melatonin while light causes that production to stop. As a result, melatonin helps regulate our circadian rhythm and synchronize our sleep-wake cycle with day and night. In doing so, melatonin facilitates our body’s transition to sleep[5] and promotes consistent and quality rest. But blue light at night interferes with our body’s ability to produce melatonin. Because the brain doesn’t distinguish between blue light from the sun versus blue light from our cellphones, our brains think its time to be awake.
Exposure to blue light at night from electronic devices can lead to poor sleep quality, difficulty falling asleep and daytime fatigue because it messes with our body’s ability to produce melatonin. In addition to feeling grumpy, sleep deprivation has been linked to increased risk of diabetes, cardiovascular events, obesity, depression, lower sex drive and reduced immune system function.
Seeing the Light
The damaging effect of blue light is a cumulative process. Fortunately, there are protective measures we can take to safeguard our vision and diminish the risks of long-term damage. Key nutrients play critical roles in protecting the eyes from photo-oxidative damage, particularly the macular carotenoids: lutein and zeaxanthin.
Lutein and zeaxanthin are carotenoid pigments that impart yellow or orange color to various foods such as cantaloupe, pasta, corn, carrots, orange/yellow peppers, fish, salmon and eggs. Despite their bright food coloring abilities, these carotenoids are also found in leafy green vegetables. In fact, kale is one of the best sources of lutein. The chlorophyll in dark-green vegetables masks the lutein and zeaxanthin pigments – hence their green appearance. Other green sources of these carotenoids are parsley, spinach, broccoli and peas.
In the eye, lutein and zeaxanthin are the only carotenoids found in the lens and are powerful antioxidants. Research shows that both can protect the lens’s proteins, lipids and DNA from oxidative damage and are able to absorb short wave blue light.[6] Differences in the form and function between the two carotenoids is also synergistic, with zeaxanthin predominant where cone density is highest and risk of oxidative damage is greatest, meaning it has more potent antioxidant effects and prevents lipid peroxidation by UV light. While lutein is thought to be more effective at light filtering.
Lutein and zeaxanthin are also selectively absorbed and sequestered in the retina. Increased dietary intake of lutein and zeaxanthin is associated with increased macular pigment density (the thickness of the protective layer of carotenoids in the macula) in healthy adults.[7] Epidemiological studies have reported an inverse association between dietary intake of lutein and zeaxanthin and the risk of developing age-related ocular diseases such as AMD and cataracts. Researchers have established that the basic biology of the macular carotenoids is protecting the retina and supporting visual performance by acting as blue light filters, quenching ROS and inhibiting lipid peroxidation of cellular membranes generated from photo-oxidation.
In addition to eating more lutein and zeaxanthin rich foods, you can also do the following to prevent long-term damage to your eyes:
- Limit screen time and take frequent breaks to give eyes a rest. Avoid bright screens up to three hours before bedtime
- Use artificial tears when your eyes feel dry
- Wear computer glasses with yellow-tinted lenses that can reduce blue light and increase contrast on screens
- Put protective blue-light filters on computers, tablets and phones. Reduce the amount of blue light emitted from devices, which also will protect your screen
- Use glare-reducing and anti-reflective coatings, which also block blue light
[1] Zhao, Zhi-Chun et al. “Research progress about the effect and prevention of blue light on eyes.” International journal of ophthalmology vol. 11,12 1999-2003. 18 Dec. 2018, doi:10.18240/ijo.2018.12.20
[2] Izzotti A, Bagnis A, Saccà SC. The role of oxidative stress in glaucoma. Mutat Res. 2006 Mar;612(2):105-14. doi: 10.1016/j.mrrev.2005.11.001. Epub 2006 Jan 18. PMID: 16413223.
[3] Nita M, Grzybowski A. The Role of the Reactive Oxygen Species and Oxidative Stress in the Pathomechanism of the Age-Related Ocular Diseases and Other Pathologies of the Anterior and Posterior Eye Segments in Adults. Oxid Med Cell Longev. 2016;2016:3164734. doi: 10.1155/2016/3164734. Epub 2016 Jan 10. PMID: 26881021; PMCID: PMC4736974.
[4] Xie C, Li X, Tong J, Gu Y, Shen Y. Effects of white light-emitting diode (LED) light exposure with different correlated color temperatures (CCTs) on human lens epithelial cells in culture. Photochem Photobiol. 2014 Jul-Aug;90(4):853-9. doi: 10.1111/php.12250. Epub 2014 Feb 25. PMID: 24483628.
[5] Rajaratnam SM, Middleton B, Stone BM, Arendt J, Dijk DJ. Melatonin advances the circadian timing of EEG sleep and directly facilitates sleep without altering its duration in extended sleep opportunities in humans. J Physiol. 2004 Nov 15;561(Pt 1):339-51. doi: 10.1113/jphysiol.2004.073742. Epub 2004 Sep 30. PMID: 15459246; PMCID: PMC1665336.
[6] Zhao, Zhi-Chun et al. “Research progress about the effect and prevention of blue light on eyes.” International journal of ophthalmology vol. 11,12 1999-2003. 18 Dec. 2018, doi:10.18240/ijo.2018.12.20
[7] Bone RA, Landrum JT, Guerra LH, Ruiz CA. Lutein and zeaxanthin dietary supplements raise macular pigment density and serum concentrations of these carotenoids in humans. J Nutr. 2003 Apr;133(4):992-8. doi: 10.1093/jn/133.4.992. Erratum in: J Nutr. 2003 Jun;133(6):1953. PMID: 12672909.