Where Is Blue Light Found? How Does It Affect the Eyes?

What Is Blue Light?

Where Is Blue Light Found? How Does It Affect the Eyes?

Light with wavelengths shorter than 380 nm cannot be seen by the human eye. However, wavelengths in the range of 300 to 400 nm can still pass through the cornea and be absorbed by the pupil or iris. Among them, blue light with wavelengths between 415 nm and 455 nm (high-energy, short-wavelength blue light) is considered the most harmful and is directly associated with light-induced eye damage.

In terms of classification, blue light is divided into two main groups:

• Blue-violet light: has the highest energy and is considered to pose the greatest risk to the eyes if exposure is prolonged.
• Blue-turquoise (blue-cyan) light: plays a certain role in regulating the circadian rhythm and maintaining alertness.

In modern life, people are exposed to blue light more than ever, especially from digital devices used daily.

Overview of the Effects of Blue Light

When high-energy blue light shines directly into the eyes, it can pass through the cornea and the crystalline lens to reach the retina, thereby causing conditions such as dry eye, cataracts, and age-related macular degeneration. The direct transmission of light through the transparent structures of the eye and its impact on the retina can lead to irreversible photochemical retinal damage. For these reasons, prolonged exposure to blue light can accelerate eye fatigue and contribute to the development of nearsightedness.

Blue light can also stimulate the brain, reduce the secretion of the hormone melatonin, and increase the production of adrenal hormones, thereby affecting hormonal balance and directly impacting sleep quality. This can reduce parasympathetic nervous system activity and decrease tear secretion, contributing to dry eye.

Similarly, sleep disorders caused by blue light may also be influenced by the aging (yellowing) of the crystalline lens, which reduces the amount of blue light transmitted to the retina.

Where Is Blue Light Found?

Where Is Blue Light Found?

1. Natural Sources of Blue Light

The largest natural source of blue light is the sun. Blue light from sunlight plays an important role in:

• Maintaining alertness and concentration
• Regulating the biological clock
• Improving mood and daytime work performance

When exposed to natural blue light during the daytime, the body is properly “awakened” according to its circadian rhythm, helping the mind stay clear and alert.

2. Artificial Sources of Blue Light

Artificial blue light is emitted from many devices in modern life, including:

• LED and fluorescent lights, which emit approximately 20–25% blue light
• Electronic screens (smartphones, computers, televisions, tablets), which can emit up to 30–35% blue light
• Indoor and office lighting systems

It is important to note that although the intensity of blue light from these devices is lower than that of sunlight, the very close viewing distance and prolonged usage significantly increase the risk of visual impairment.

Some common blue light wavelengths emitted by electronic devices include:

• Smartphones: ~455 nm
• Computers, laptops, televisions: ~450 nm
• LED desk lamps: ~435 nm

All of these fall within the range of blue light that can be harmful if not properly controlled.

Solutions to Reduce the Harmful Effects of Blue Light

Solutions to Reduce the Harmful Effects of Blue Light

To protect your eyes from blue light in modern life, you can apply the following measures:

• Take regular breaks for your eyes and apply the 20–20–20 rule
• Limit continuous use of electronic devices for long periods
• Maintain an appropriate distance between your eyes and the screen
• Use blue light filtering modes or adjust screen brightness
• Consider using blue light–blocking glasses under a doctor’s guidance
• Use lubricating eye drops to maintain moisture and reduce dryness
• Supplement eye-healthy vitamins such as A, C, E, B6, B12, and B9
• Have comprehensive eye examinations at least twice a year

Under conditions where blue light–blocking glasses are used or when there is no exposure to blue light, sleep quality is significantly improved, as shown by increased sleep efficiency and reduced time to fall asleep. However, in some studies, the use of electronic devices did not show a significant negative effect on sleep characteristics.

Blue light is not entirely harmful; however, prolonged and uncontrolled exposure—especially from electronic devices—can cause serious problems for the eyes and overall health. Understanding what blue light is, where it comes from, and how it affects the eyes will help you proactively protect your vision in the digital age.