The Blue Light Hazard

In the past few years there has been increasing worry among vision scientists and eye care providers over the “Blue Light Hazard”.

Short wavelengths of light have higher energy than longer wavelengths. In the Visual Spectrum Red is the longest wavelength, then Orange, Yellow, Green, Blue (Indigo maybe) and Violet- you will remember that from school.

Next to Violet is UltraViolet, often called UV “Light”, but because light is part of the visual spectrum (The narrow band of the electromagnetic spectrum to which our eyes are sensitive), and because we cannot see UV, it should not be called light, it is radiation. Beside UV in the EM spectrum is X-Rays, which again we cannot see, but by now most people should be aware of the dangers of X-Rays, then Gamma-Rays and higher energy radiation.

Much of the UV radiation which arrives at the eye is absorbed- it can cause damage to the front of the eye and the lens inside the eye- causing cataract, but most cannot penetrate to the light sensitive retina at the back of the eye- HEV Light can. Scientists have been using this fact for sometime- using HEV Light on mice and rats to damage their retinas prematurely- causing premature age related macular degeneration to try to understand what can be done to protect human eyes. That may be cruel, but much knowledge has been gained in the fight against AMD in humans from experiments like those.

Clinicians have long been aware of the risk of intense High Energy Visible (HEV) Light- eye doctors try to minimise the eyes’ exposure to intense operating theatre lights, and optometrists use minimal strengths of illumination when looking into the eyes with ophthalmoscopes and slit lamps, often also employing protective filters to further reduce the exposure. While these are examples are of intense lights, there is also thought to be a risk of HEV exposure using modern electronic equipment- computers, tablets and phones.

Fluorescent lights, and the illumination systems of modern monitors are capable of producing enough HEV Light that the experts say there could be a cause for concern. My first thoughts when I was told about the new spectacle coatings which can minimise the exposure to this risk was “Just change the colour temperature of the monitor”. Many monitors have a selection for Warm Cool or Neutral, some others allow the user to select a preset Colour Temperature- the higher the colour temperature, the more bluish the output. If you sit at a screen 7 to 8 hours per day, it would be worth having a look at the settings of the monitor to adjust this- it will at least minimise HEV Light exposure.

Unfortunately, most phones and tablets do not come with any way to adjust the colour temperature of the screen, which means there is no way to reduce the blue output, which is why many manufacturers are now offering “Blue Control” Antireflective coatings. These coatings often have a blue reflection, rather than the more common green. The colour of an antireflective coating until recently had been thought to be a mainly cosmetic consideration- Asian manufacturers tended to make Magenta coloured coatings, European ones Green, because that colour was thought to suit the Asian and European skin tones better.

Blue control lenses work by preferentially reducing the transmission of the blue and violet HEV wavelengths. Much like putting on brown tinted sunglasses, where everything looks brown for a few seconds and then you don’t notice it, with a Blue Control coating everything does look very slightly yellower for a moment of two. You wouldn’t notice unless you were looking at the monitor and putting them on and off- the effect is that subtle, but they do reduce exposure to the harmful wavelengths.

With children and teenagers spending hours staring at laptops, tablets and phones, it may be advisable to consider a protective coating for them.


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