Blue light is a visible light spectrum with the shortest wavelength and highest energy. This light can pass straight through the retina of the eyes via the cornea and lens. Sunlight is the largest source of blue light and being outdoors gives a person maximum exposure to blue light during the daytime.
Laptops, flat-screen televisions, tablets and smartphones are manmade sources of blue light that mimic daylight. Blue light exposure from screens is less than the amount of exposure from the sun. However, because of the close proximity to screens and the length of time spent on them, there is an increased risk of blue light from screens causing eye damage. Exposure to blue light affects the sleep-and-wake cycle, or circadian rhythm, by altering the synthesis of melatonin in the brain.
What are the harmful effects of blue light?
Direct penetration of crystals into the retina causes irreversible photochemical retinal damage. A wavelength between 300 and 400 nm can penetrate the cornea and be absorbed by the iris (the colored disc in the eyes) or pupil (the black center within the iris). High-energy short-wave blue light between 415 and 455 nm is the most harmful. Because people have been gradually realizing the harmful effects of blue light, eye discomfort related to blue light is becoming a more prevalent concern.
Continued exposure to blue light could lead to
- Myopia (nearsightedness): Because of blue light's short wavelength, the focus is not in the center of the retina, but rather in the front of the retina. This means that longer exposure time to blue light causes worsening visual fatigue and nearsightedness. Symptoms such as diplopia and inability to concentrate can affect the ability to learn and work efficiently.
- Cataract formation: The lens contains structural proteins, enzymes and protein metabolites that absorb short-wave light. Absorption of blue light by the lens increases significantly, thus blocking potential retinal damage from blue light. However, when it exerts its protective effect on the retina, the lens undergoes a decrease in transparency or color change, which leads to cataract formation.
- Eye strain: Blue light from computer screens and digital devices can reduce contrast leading to eye strain. Fatigue, dry eyes, bad lighting or how you sit in front of the computer can cause eye strain. Symptoms of eye strain include sore or irritated eyes and difficulty focusing.
- Retina damage: Continued exposure to blue light over time could lead to damaged retinal cells. This can cause vision problems such as age-related macular degeneration.
- Glaucoma: Increased incidences of increased eye pressure are seen in those exposed to blue light for a long time.
What are the benefits of blue light?
Blue light has several benefits that include
- Boosting alertness, helping memory and cognitive function and elevating mood.
- Regulating circadian rhythm—the body’s natural wake and sleep cycle. Blue light can regulate the body clock. It stimulates the secretion of melatonin in the pineal gland that can increase or decrease cortisol expression depending on the time of day and it regulates the human circadian rhythm.
- Maintaining a healthful circadian rhythm. Too much exposure to blue light late at night (through smartphones, tablets and computers) can disturb the sleep-wake cycle, leading to problems sleeping and daytime tiredness.
- Supporting the growth and development of childrens’ eyes and vision. A deficiency in natural blue light exposure could contribute to the recent increase in myopia/nearsightedness.
- Benefiting the skin by treating acne, psoriasis and other skin problems.
How can eye damage due to blue light be prevented?
The prevention and control of blue light damage are becoming more and more important and blue light blocking products are constantly emerging. Blue wavelengths that are beneficial during daylight hours are most disruptive at night.
Constant exposure to blue light from smartphones, tablets and computer screens can be decreased by
- Limiting the screen time.
- Using good quality screen filters.
- Using yellow-tinted computer glasses.
- Using anti-reflective lenses.
- Using screen guards.
- Using night mode when possible.
- Keeping brightness settings to 50 percent.
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American Academy of Ophthalmology