Did you know blue light can be both essential and harmful to eye health? Some forms of blue light help us to see properly and control our circadian rhythms, whereas continued exposure to bad blue light, from smartphones for example, can be harmful and lead to conditions like age-related macular degeneration (AMD).
Understanding the whole spectrum of blue light is important, as it teaches us how the eyes work and how to protect and preserve sight.
A guide to UV and blue light
Sunlight contains ultraviolet (UV) and blue light; UV is part of the non-visible light spectrum while blue light is part of the visible.
We are exposed to UV light from the sun every day, and the cumulative effect of this exposure can damage the front of our eyes, the cornea and the lens, which can cause cataracts. However, the cornea and the lens are essentially very effective at blocking UV rays; less than 1% of UV radiation from the sun reaches the retina.
Blue light, however, is different. It is part of the visible spectrum and reaches far deeper into the eye, as far as the retina. Nearly all visible blue light passes through the lens and cornea to the retina.
We are exposed to blue light from the sun’s UV rays; usually around 25-30% of the sun’s rays are made up of this light source. However, the most significant problem for eye health is our exposure to blue light from LEDs and compact fluorescent lighting (CFLs).
LEDs contain around 35% blue light and CFLs around 25%. It is expected 90% of our total light exposure will be via LEDs by the year 2020.
How does blue light harm our eye health?
When we talk about harmful blue light it is very important to distinguish the particular kind of blue light we are talking about, namely blue-violet light. All blue light reaches the retina and this type in particular damages it.
In 2008, prescription lens manufacturer, Essilor, partnered with the Paris Vision Institute to find the bands of visible (blue) light that caused the most retinal cell death. They split light into several bands and then exposed porcine retinal pigment epithelial (RPE) cells to each band for several hours at a time. 415 to 455 nanometres (nm) was identified as being the most harmful to the retina, named blue-violet light.
This harmful blue-violet light is what many or all of us are increasingly exposed to when using our digital devices and spending time in artificially lit buildings. The cumulative effect is the main concern because eyes cannot block blue light, so there is the risk of retinal death. This in turn can develop into AMD.
When is blue light good for us?
To bring some perspective to the blue light issue, there is one type of blue light that is actually essential to our health, and not just our eyes.
Defined as blue-turquoise light, it is at 465 – 495 nm and controls our pupillary reflex, memory and brain performance as well as our sleep/wake cycle, otherwise known as circadian rhythm.
Ensuring the good, blocking the bad
Protecting against bad blue light is not easy. Any filter needs to block harmful UV and blue-violet light but allow blue-turquoise light through.
As part of the aforementioned research, Essilor and the Paris Vision Institute developed a new lens to protect against blue-violet light. Their Light Scan lens lets in ‘good’ blue light and blocks ’bad’ blue and UV light. The front side of the lens deflects UV light and around 20% of blue-violet light, and the inside of the lens protects against reflective glare from UV light. The lens does this whilst also maintaining transparency and clarity of vision.
This is promising type of treatment but shouldn’t we also try to stop devices and lighting emitting blue-violet light in the first place? As yet manufacturers of smartphones, computer screens and LED lighting haven’t addressed the issue in any meaningful way.
Apple released a ‘Night Shift’ mode in April 2016 for iPhones and iPads with the aim of regulating the sleep/wake cycle. The feature determines when the sun has set, according to location, and changes the display to the warm end of the visible light spectrum. The amber-coloured filter, also available via specialist Android apps, is supposed to help maintain a normal sleep/wake cycle although there isn’t any research to confirm it can regulate circadian rhythm.
Screens and lighting will always emit blue light until manufacturers address the issue at source. Usage of blue-light-emitting devices and exposure to CFLs is so widespread it is not viable to rely on lenses alone, particularly as they only serve those who wear glasses. Do you think manufacturers are responsible for developing healthier devices for us to use?
Blue light remains high on the agenda as a public health issue, and researchers and manufacturers can work together in the future to find solutions to protect sight for life. To delve deeper into the issue of blue light, read our infographic or find out more about how you can protect against it.