Blue light has been the hot topic in spectacle lens development lately.  While we have known for years about the damaging effects of UV light (cataract, macular degeneration, pterigium), recent evidence is suggesting that the short wavelength end of the visible spectrum may also cause damage to our eyes over time.  It has also been suggested that blue light exposure at night may affect our ability to get a good nights sleep.  This is of concern as the amount of blue light we are exposed to has increased dramatically in the past decade, due to increased use of mobile phones and tablet devices. 

As wavelength increases, light gradually moves from invisible ultra-violet (UV), through to visible blue, and on through to red.  Beyond the end of the visible red spectrum lies infra-red light, which we can't see but can detect as heat. The area of recent concern is shown in the diagram below.

Research has demonstrated that nighttime light exposure, particularly to blue light, suppresses the production of melatonin.  Melatonin is secreted by the pineal gland, and is the major hormone that controls sleep and wake cycles. A reduction in melatonin at night is therefore associated with subjective levels of sleeplessness.  If you've ever spent too long on your computer at night, and then found it hard to get to sleep despite being tired, this may explain why.

Additionally, there is now good evidence that blue light, and not just UV, is implicated in the serious eye condition macular degeneration.

To help combat these effects of blue light, lens manufacturers have been developing treatments specifically to block these wavelengths.  Essilor's Crizal Prevencia has been developed to selectively filter blue light, improving comfort on a screen and reducing the amount of blue light reaching the retina.

If you have a family history of macular degeneration, or spend a lot of time in front of a screen, it may be worth considering whether Crizal Prevencia could be right for you.