Is blue light dangerous?
The largest source of blue light is the sun and its reflections from surfaces like water, beaches, cars and windows. Other sources are home lighting, especially LED bulbs and digital devices.
Lots of people, including scientists and ophthalmic/optometric experts, mistakenly think that since digital devices are not as intense as the sun that they are not dangerous and therefore do not contribute to photochemical damage that can eventually lead to age-related macular degeneration. This is simply not true!
Blue photons carry the same amount of energy per photon, whether they come from the sun or your phone. What matters is your life-long exposure not the intensity.
What is blue light?
Electromagnetic radiation is divided into bands along a spectrum according to the frequency of the waves it emits.
Humans can see electromagnetic radiation with wavelengths between 380 nanometres (nm) and 760 nm; this is therefore called the visible part of the electromagnetic spectrum or light.
Blue light is the bottom 3rd of the visible spectrum and sits between 380 nm and 500 nm. . It includes violet, blue and turquoise.
Shorter wavelength light carries more energy per photon and can therefore be more damaging to cells.
What is the risk to the retina?
Based on over 50 years of research, the ISO (International Organisation for Standardisation) has identified the risk of retinal damage by light at various wavelengths. Their aphakic hazard function (red line in the plot) shows the danger to that eye that would exists if the lens and cornea were not present. This extends from UV through violet and blue (300-500 nm).
While UV radiation, which sits just beyond the visible spectrum, carries enough energy to damage cells and mutate DNA, it is, in adults, almost completely blocked by the cornea and lens (grey media transmission line) and so does not reach the back of the eye.
What remains is the retinal or blue light hazard function (blue filled area). It is this part of the visible spectrum that contributes to the long-term accumulation of damage that speeds up the ageing process or our retina and according to a recent French Health and Safety Authority (ANSES) report is now a proven cause of age-related macular degeneration.
How does blue light Affect the Eye?
Over time, the blue light that reaches the retina leads to the formation of reactive oxygen species or free radicals that can also damage proteins, phosopholipids, RNA and DNA.
While some of this damage can be repaired, certain types of DNA and mitochondrial DNA damage cannot. Over the long term, the accumulation of such damage leads to compromised cell function and the accumulation of lipofuscin and drusen, which are the first signs of impending macular degeneration.
Unlike skin cells that regenerate every five days, your retinal cells are with you for life. Therefore, any damage they incur is permanent.
How can we protect the retina?
Reducing the amount of blue light that we are exposed to, reduces the risk of damage from blue light. Simple strategies such as limiting time in the sun and wearing sunglasses all help.
We also have a natural protective layer at the back of the eye that specifically protects us from blue light.
Macular pigments absorb light wavelengths that are the most damaging to the retina (400–500 nm). In fact, they absorb as much as 90% of blue light before it hits the retina, protecting the retinal cells from damage.
The problem is you can’t tell how much macular pigment someone has just by looking at them. Macular pigment density is affected by genetics, diet, obesity, fitness, cigarette smoke, and blue light exposure.
The positives...
While blue light poses a long-term risk to the retina, parts of the blue light spectrum are also necessary for setting our sleep-wake (circadian) cycle. A pigment in our retina called melanopsin uses blue light at 480 nm (turquoise) to signal to our body that it is daytime.
We need this “good” blue light in the morning to stop the secretion of melatonin, which helps us feel alert and alive! But in the evenings, an hour or two before bedtime, we should avoid this same “good” blue light so that our body starts producing melatonin again to help us get to sleep.
For this reason, the ISO recommends that blue light filtering lenses filter out some of the “bad” blue light (380-455 nm) and allow transmission of the “good” blue (455-500 nm).
Why have an MP-eye test?
The MP-eye quickly and easily assesses macular pigment levels in the eye, to identify those with low levels of natural protection against violet-blue light and oxidative damage.
Eye care professionals can then advise those with low protection on lifestyle improvements and available products that help them protect their vision.