Is Blue Light Actually Bad for Your Eyes?: A Comprehensive Guide

To understand whether blue light might damage eyesight, it is important to understand what it is and how our exposure to it has changed in recent years. 

Digital device usage has increased substantially in recent years across all age groups. A 2020 study estimated that adults typically spend on average 4 hours 48 min per day using digital media.

These changes have been associated with various negative symptoms associated with digital eye strain: eye pain, headaches, increased sensitivity to light, redness and watering of the eyes, dry eyes, blurry vision, etc.. 

Most of these symptoms can resolve with rest and reduced screen time. However, can the light emitted by digital devices have a long-term and even permanent detrimental effect on the health of our eyes? 

To answer this question, we have to take a closer look at the nature of the light produced by digital displays. 

Digital displays are illuminated by LEDs (light-emitting diodes ). These are chosen for their energy efficiency, durability, and small size. The most common type of LED generates white light by coating a blue LED with a yellow phosphor, a substance that emits light when exposed to certain radiations; when blue light passes through the phosphor coating, it mixes with yellow light to simulate white light. 

Every light colour has a range of wavelengths: blue light is around 435 - 500nm, yellow light is around 565 - 590nm, and red light is around 625 - 740nm. As illustrated in the graph above, white LEDs shows a clear peak at around 470nm, within the blue-light range. They emit far more blue light than incandescent and fluorescent lights. 

Currently, smartphones and premiums tend to use OLED (organic light-emitting diode) or AMOLED (active-matrix organic light-emitting diode) displays. In contrast to traditional LCD (liquid crystal display) screens, which are backlit, every pixel of an OLED/AMOLED screen emits its own light. It means that significantly more light, especially blue light, enters the viewer’s eyes directly.

Furthermore, technology companies have been increasing screen brightness. Luminance, the objective measure of brightness, is calculated in candela per square metre ( cd/m²), which is equivalent to ‘nit’. 1 cd/m² or 1 nit is roughly the brightness of a wax candle's light emitted, transmitted, or reflected by a surface of 1 square metre. Over the past decade, the luminance of iPhones has quadrupled: iPhone 5 of 2012 had a maximum luminance of 500 nits; by contrast, today, iPhone 14 Pro Max can reach a peak luminance of 2000 nits when less than 25% of the screen is lit up.

Admittedly, even the brightest OLED screen at the moment emits less light than a sunny sky. However, as ophthalmologist Dr Jean Leid points out, what matters is not the ‘total amount of light emitted’ by a light source but the amount that enters the eye. With the use of digital devices, there are multiple causes for concern: we look at the screens directly at a very close distance; we use the devices for long durations; we are also less likely to use protection. 

Blue light exposure has greatly increased with the proliferation of LED-based digital devices. To explore whether blue light may damage the eye, we have to understand how the eye works and how light may damage it.

In the eye, the main cells responsible for detecting light are called rods and cones. These cells are situated in the retina, and they contain pigments, molecules that detect specific wavelengths of light and tell the brain when and where they were detected. It is through this process that we perceive visual images.

When light is detected, the pigments are bleached by photons and trigger a cascade of chemical reactions. One by-product of these reactions is reactive oxygen species. They are molecules that contain oxygen and unstable electron configurations. In order to stabilise, they react with other molecules to gain more electrons. This reaction can destabilise other molecules and trigger a series of reactions known as cytotoxic chain-reactions (cytotoxic: toxic to living cells). 

These reactions can be triggered by many other factors and occur anywhere in the body. They can cause cellular damage and even cell death. An overabundance of reactive oxygen species, which leads to oxidative stress, has been implicated in the development of many diseases, such as cancer, asthma, pulmonary hypertension, and retinopathy.

Of course, the eyes are organs that have evolved to absorb light. Light-absorbing cells in the eyes are equipped with mechanisms to mitigate the effect of reactive oxygen species: they contain antioxidants, which react with reactive oxygen species and “deactivate” them. This prevents them from causing damage to the cell.

In the retina, two important antioxidants are lutein and zeaxanthin. They exist within rods and cones in high concentration in order to mop up the high levels of reactive oxygen species made. However, if the rate of reactive oxygen species production exceeds the antioxidant capacity of the cells, oxidative damage can occur.

The generation of reactive oxygen species during pigment bleaching is true of all wavelengths of light. The absorption of too much of any wavelength can lead to this light-induced photochemical damage. However, many animal and cell studies have shown that exposure to blue light damages the retina significantly more than any other wavelength of visible light. Why is this?

It is well known that UV is harmful for your eyes. UV rays, which are invisible, have shorter wavelengths and higher energy than visible light. They can trigger photochemical reactions that generate a lot of reactive oxygen species.

Blue light is only one level above UV on the light spectrum: among all colours of visible light, it has the lowest range of wavelengths and the highest amount of energy. In the eye, while most of UV light is absorbed by the lens and does not reach the retina, most of blue light is not filtered and reaches the retina.

Apart from its higher intensity and greater penetration, blue light might also cause more damage than other colours of visible light because of a special property. After light breaches a retinal pigment, the pigment needs to be “reset” in order to absorb light again. Blue light appears to be able to reset pigments, specifically rhodopsin (visual purple) in rod cells, at a much faster rate. This means that if your eyes are exposed to green light, for example, the pigments don't absorb too much light because it takes so much time for them to reset. On the other hand, with blue light, the light-absorbing pigments are almost immediately reset, which means more light is absorbed and more reactive oxygen species are generated. 

There is a substantial body of in-vitro and animal studies that suggest blue light can cause damage to photoreceptors and the retina, as well as other parts of the eyes such as the cornea and the lens. Some scientists conjecture that blue light might also accelerate vitreous degeneration and cause eye floaters.

However, this is not to say that blue light is unequivocally dangerous. Some authorities, such as the European Commission's Scientific Committee on Health, Environmental and Emerging Risks (SCHEER) and the International Commission on Illumination (CIE), have declared that photochemical damage from daily blue light exposure is insignificant. In-vitro and in-vivo animal studies may not accurately reflect the effects of blue light on human eyes. Furthermore, it remains unclear whether daily exposure to blue light from digital devices can reach the thresholds required to trigger permanent damage in human eyes. More research is needed to fully understand how blue light may affect eye health.

Nonetheless, it might be injudicious to suggest that blue light is simply harmless because of a lack of definitive longitudinal studies on human subjects. The explosive increase in screen time and the gradual increase in screen brightness are both recent developments, whose long-term effects have yet to be seen. Based on the current scientific evidence, it would be sensible to beware of blue light exposure and err on the side of caution.

Everyone has different amounts of daily exposure to blue light. It would be a good start to consider how much blue light you are exposed to every day: 

• Do you spend prolonged periods outdoors?
• Do you wear sunglasses outdoors?
• What kind of lighting do you have at home and at work?
• How many hours do you spend in front of LED screens every day?
• Do you take regular breaks from screen use?
• What are the brightness levels of your digital devices?

Blue light also has different levels of impact on different groups of individuals because of physiological differences. In individuals under 20, the lens is clear, which allows more blue light to pass through. In children's eyes, around 90% of blue light at 450nm reaches the retina; by contrast, less than 70-80% of light under 540nm reaches an older person's retina. However, it does not mean that the elderly are safe from the effects of blue light; older people have lower antioxidant capacity and are more prone to oxidative damage. People with intraocular lens implants that do not filter blue light also get more blue light exposure.

Another relevant issue is timing. Blue light plays an important role in regulating the circadian rhythm, which is the body’s internal clock. In the morning, blue light can suppress the levels of melatonin, a hormone that induces sleepiness, and thereby promote alertness and productivity. Therefore, it is a good idea to go outside for a walk soon after you wake up. In the evening, however, blue light can delay the onset of melatonin production and disrupt the circadian rhythm. Consequently, it is advisable to minimise blue light exposure in the evening, especially before sleep.

To protect your eyes from blue light, there are various ways:

Electronic devices are a main contributor of blue light exposure, and they also lead to digital eye strain or computer vision syndrome, which has a variety of negative symptoms such as dry and irritated eyes.

You should take regular breaks from screen use. 20-20-20 rule suggests that every 20 minutes, you should look away at someone 20 feet away for twenty seconds.

You can also use apps to track and control your screen time.

You should reduce the brightness of your screens. On iPhones, you can also reduce white light, which contains more blue light (Settings —> Accessibility —> Display & Text Size —> Reduce White Point).

You can reduce blue light emission from your screens by adding a tint to the screen. Many smartphones have blue light filters: iPhones have Night Shift; Android devices have Night Mode/Night Light; Samsung phones have Blue Light Filter. You can turn on the Dark Mode on your phone, browser, or computer to reduce the overall amount of white light. There are also third-party apps such as f.lux.

Many spectacles come with lenses that filter blue light, and there are also tinted blue-light-blocking glasses specifically designed for that purpose. It is noteworthy that not all lenses are equally effective: some lenses filter a much lower percentage of blue light than others. A general rule of thumb is that the darker and warmer the tint, the stronger the protection. Most blue-light-blocking glasses also offer UV protection. 

As blue light can lead to increased levels of reactive oxygen species, it is also important to ensure ocular cells are supplied with sufficient antioxidants to neutralise them.

Various studies show that antioxidants, especially lutein and zeaxanthin, can limit the damaging effect of reactive oxygen species in the eye.

Lutein and zeaxanthin can also absorb blue light. These antioxidants can be found in a variety of foods and also sourced from supplements. Theia Bio's Clearer™, for example, contains not only lutein and zeaxanthin but also other antioxidants with proven benefits for eye health, such as citrus aurantium, vitamin C, and zinc. 

People over the age of 40 should be particularly attentive to nutrition because the body’s antioxidant capacity decreases with age.

If you want to reduce blue light exposure, you should consider using warmer LED lighting at home. Fluorescent lighting, which is commonly used in offices and classrooms, contains not only higher levels of blue light but also more UV. 

There has been a significant increase in blue light exposure in recent years. Many factors have contributed to an exponential increase in screen time: the proliferation of smartphones and tablets, the popularity of social media, remote working… Meanwhile, digital screens powered by LED technologies have also become much brighter, resulting in greater amounts of blue light.   

With its short wavelength and high energy, blue light can reach the retina, induce photochemical reactions, and trigger oxidative stress. There is a substantial body of in-vitro and animal studies that indicate blue light’s potential to damage retinal cells. In other parts of the eye, blue light might also cause oxidative damage.

However, whether daily exposure to blue light can cause long-term and permanent damage to the eye remains a topic of debate, because there is currently a lack of human studies that definitively prove such damage. There is heated disagreement between experts and authorities.

Meanwhile, it is worth remembering that the increase in blue light exposure is a recent phenomenon, and the long-term effects have yet to be seen. There are good reasons to reduce blue light exposure, especially because it is associated with not only potential phototoxicity but also other well-attested negative effects such as digital eye strain and disruption to the circadian rhythm.

Simple behavioural changes can reduce blue light exposure and mitigate the risks of blue light damage. Methods such as limiting screen time and ensuring a sufficient intake of antioxidants are risk-free and have extensive benefits for eye health.