1. Just several hours of exposure to blue light (wavelength between 415nm and 455nm) cause retinal cell death.
2. Blue light exposure from lamps, computer screens, tablets and smartphones is lower than looking at a clear blue sky.
For the answer... read more...
The spectrum of light; (Wavelengths in nano-meters) - the shorter the wavelength, the more damaging the energy
Invisible Radiation; UltraViolet (300 to 400nm)
The body of research on the visible spectrum and particular wavelengths of light is immense and while some effects of exposure are well established, others are still being investigated.
On the one hand, light is essential for many functions;
It helps us to see better, it helps us with our visual acuity and contrast acuity, it helps us perceive colours, and it helps with various non-visual functions of the body e.g. maintaining and regulating the sleep/wake cycle. which in turn affect memory, mood and hormonal balance.
But on the other hand, some components of natural light can be harmful to the cells of our bodies;
The harmful rays tend to be mainly in the short wavelength (Violet) end of the spectrum. The potential damage from light will depend on a combination of its wavelength, its intensity and the length of time exposed to it. It is the cumulative effect of these that does the damage. Many countries have guidelines for overall exposure to different wavelengths of light. The biological evidence of such light hazards is reviewed periodically, to set levels below which adverse health effects are unlikely.
Most people are aware that light in the Ultra-Violet and Violet regions (below 425nm) are particularly harmful to eyes.
However, the Violet-Blue range of visible light (with wavelengths between 400nm and 470nm) has now also been linked to retinal damage and cell decay following direct exposure in laboratory and animal studies. The blue light emitted from illuminated screens such as laptops, tablets and smartphones peaks around the 460nm point. The brightness, the amount of light arriving at the eye, has to be relatively low for comfortable viewing but a person using these devices for many hours each day is receiving a significant amout of light at these frequencies.
In 2008 in an effort to establish more specifically the wavelengths which are more effective than others at causing harm to the eyes researchers at the Paris Vision Institute isolated small bands of blue light wavelengths and focused each band on cells from pig retinas for several hours. They found that the band between 415 nm and 455 nm caused maximum retinal cell death (1).
In 2016 a study which assessed the blue light hazard from a variety of light sources, researchers from the Centre for Radiation, Chemical, and Environmental Hazards in the UK (2) found that in terms of blue light hazard the domestic lamps tested (incandescent, LED and CFL) ranged from 10 to 20% of the current exposure limit, assuming long-term viewing.
Tests were also run for worst-case viewing of white screens across computer monitors, laptop screens, tablet screens and smartphone screens; i.e. brightness set to maximum brightness viewed from 100mm. Computer monitors, laptop screens, tablet screens, and smartphone screens all tested below the published exposure limits, even for extended viewing times.
The authors concluded that the exposure to blue light from lamps, computer screens and mobile devices, such as smartphones is lower than for the exposure likely to be received from staring at a blue sky. Under even extreme long-term viewing conditions, none of the devices suggested cause for concern for public health.
So, the answer to the challenge above is; 1. Exposure to Blue light in the visible spectrum can cause damage to the retina.
So, Need you worry? ; Well yes, a little, as prolonged exposure is not likely to be good for you, and risks your discomfort.
We use special lens coating to control that risk, ask our staff about "Blue Control" which is our special Anti-Reflection coating designed to bring excessive blue light exposure under control.
It is generally accepted that people who use computers and digital devices for long periods commonly experience problems with their eyes. It is sometimes referred to as Computer Vision Syndrome.
The main symptoms are: Eyestrain, Tired eyes, Irritation, Burning sensation, Redness, Blurred vision.
These may be due to blue light exposure or underlying (and previously untreated) eye conditions. We are not are not well-evolved for long periods of staring directly at a close task, We often fail to blink enough while staring at the screen and it can cause drying of the front of the eye (cornea) that causes our discomfort.
If you experience discomfort problems on the computer, Shattkys optometrists can prescribe spectacles and/or the best eye drops to make your use of digital devices more comfortable!
1. Cited by Smick K et al. Blue Light Hazard: New knowledge, new approaches to maintaining ocular health. Report of a roundtable sponsored by Essilor of America. March 16, 2013, NYC, NY
2. O’Hagan JB, Khazova M, Price LL. Low-energy light bulbs, computers, tablets and the blue light hazard. Cambidge Ophthalmological Symposium. Eye 2016 30, 230-233
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