Blue light is the visible light at the blue end of the spectrum. Although not as energetic as ultraviolet (UV) light, there is concern that high doses of blue light might cause more cellular damage than longer wavelengths of visible light (which you see as the colors red through green). As well, exposure to blue light may have an impact on your sleep-wake cycle.
Sunlight and incandescent light contain a broad range of wavelengths. But the light from electronic devices and light-emitting diodes (LEDs) in lighting sources has a much narrower range of wavelengths. This increased blue light exposure from LED lights, cell phones, tablets, and laptop computers has raised concerns about the effects it may have on the sleep-wake cycle and possible damage to the eyes. However, the American Academy of Ophthalmologists does not think blue light from electronic devices is damaging to the eyes.1
How Your Eyes Process Light
There are three types of cone receptors in your eye’s retina that are keyed to different sections of the visible spectrum. Some cones are more sensitive to red, some to green, and some to blue. The signals from these receptors are integrated in your brain to produce your sense of color.
Blue light has the shortest wavelengths detectable by the human eye. The sun produces blue light along with the other colors of the spectrum, and so we are exposed to it naturally. But exposure to intense amounts of blue light may be harmful to the eyes.
The Light Spectrum
The wavelengths of light detected as visible colors are:
- Red: 625 – 740 nm
- Orange: 590 – 625 nm
- Yellow: 565 – 590 nm
- Green: 520 – 565 nm
- Cyan: 500 – 520 nm
- Blue: 435 – 500 nm
- Violet: 380 – 435 nm
Infrared is invisible and is felt as heat. It is from 1 mm to 760 nm in wavelength.
Ultraviolet is invisible and has a wavelength of less than 400 nm.
Blue Light and Macular Degeneration
One fear is that overexposure to blue light could lead to retinal damage as is seen in the development of age-related macular degeneration (AMD). Blue light and ultraviolet light place oxidative stress on the retinal pigments. This has been seen in experiments on mice.2
Although there is no direct evidence that either UV or blue light causes macular degeneration, there is epidemiologic evidence that greater exposure to these types of light increases the risk of AMD.3 People with a higher risk for the disease might protect their eyes from UV and blue light exposure.
The main risk factors for AMD are a family history of the condition, age, and cigarette smoking. There is some evidence that obesity, nutritional factors, and alcohol use disorder may also raise the risks.2
Protecting Your Eyes
Your eye doctor likely recommends quality sunglasses to protect your eyes from harmful ultraviolet light rays emitted by the sun, since ultraviolet light may contribute to the development of eyelid cancers, cataracts, pinguecula, and pterygium.
To address indoor blue light exposure, many companies market blue-blocking glasses that filter blue light. However, a systematic review of research studies in 2017 could not find high-quality evidence to support the general population wearing blue-blocking glasses for their macular health, sleep quality, or to relieve eye fatigue.4
Blue Light and the Circadian Rhythm
Before the technological age, blue light primarily came from sunlight. Human eyes have receptors that contain a photopigment called melanopsin that is sensitive to blue light.5 Exposure to blue light is detected by the eyes and signals the pineal gland to suppress the secretion of the hormone melatonin. Melatonin is a sleep hormone helps to regulate your circadian rhythm. With melatonin suppressed, you remain awake, alert, and able to go about your daily tasks and think clearly. Exposure to blue light in the evening and at night might continue to suppress melatonin, resulting in a disruption of the wake-sleep cycle.6
Concerns are especially common for blue light exposure from electronic devices before or at bedtime. Tips for getting a better night’s sleep include switching off electronic screens before bedtime, keeping them out of the bedroom, and ensuring the sleep environment is kept dark. As well, some devices have a night mode with reduced amounts of blue light.7
A Word From Verywell
Maintaining eye health and getting a good night’s sleep are both areas of concern throughout life, but especially as you age. Ask your optometrist or ophthalmologist if you’re at particular risk for eye conditions and get regular check-ups. Discuss sleep-related issues with your primary care provider and make your bedroom a tranquil place free of distractions.
Author: Troy Bedinghaus
Source: Very Well Health: Effect of Blue Light Exposure on Eyes and Sleep