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Effects of Blue Light on Vision Ian Pyzer Most of us would readily accept, if asked, that there is an established and unquestionable link between the exposure of our skin to excessive sunlight and a variety of conditions, ranging from accelerated ageing or wrinkles, to more serious health issues such as skin cancer. Consequently it may come as no surprise that the eye, being the very organ that concentrates and focuses light, is also prone to its more damaging effects. It is Ultra Violet (UV) light, that part of the spectrum which is invisible to the human eye, that rightly gets a lot of adverse publicity. It is the UV, with its high energy radiation, that is absorbed by the crystalline lens in the eye and is a widely accepted cause of cataracts. For this reason we are rightly advised to ensure that sunglasses are 100% UV absorbing. However, with around 99% of the UV that enters the eye being absorbed by the crystalline lens, it is clear that the delicate light sensitive retina, is in fact well protected from this. With only around 1% of UV reaching the retina, we can conclude that UV plays little part in the damage of retinal cells – but what about visible blue light? Where invisible UV stops in the spectrum, the visible colours begin. The first part of the visible spectrum is the High Energy Visible (HEV) Blue light, which is by nature scattered & diffused short wave light. Ultra Violet High Energy Visible Light Infra Red Low Energy A young healthy eye has a degree of protection. Just as our skin contains the pigment Melanin to protect itself from harmful rays, we find this same substance in the eye. Here, the presence of Melanin has a similar function to the black paint in the back of a camera. By absorbing the HEV Blue light, the Melanin stops it being reflected and scattered, which would otherwise prevent the formation of a clear image on the retina. Unfortunately, Melanin levels steadily reduce as we grow older, coinciding with the retina’s increasing failure to absorb sufficient quantities of vital antioxidants and its more sluggish removal of metabolic waste products. Consequently, the loss of ocular Melanin in the aging eye increases the risk of cell damage to the retina. The protection against HEV blue light is seriously reduced. Aside from this it is also the cause of common symptoms often experienced by those with retinal degenerations. These include: excessive glare, reduced contrast, visual discomfort and poor light adaptation when moving from sun to shade. It is once again the scattered and diffused short wave Blue light, which is to blame here! Bouncing around chaotically as it enters the eye and without a rich content of Melanin to absorb it, it scatters causing the hazy effect we term ‘glare’. Glare not only causes discomfort, but reduces image quality and contrast too. With the ageing eye’s low Melanin level and the subsequently poor absorption of HEV, the retinal cells are subjected to large doses of Blue light, which increases cell death rate and reduces their ability to recover once light intensity drops ie when moving back into the shade, leading to poor adaptation. Sunglasses may absorb 100% UV as will various UV ‘over-specs’, but as we have seen, very little UV reaches the retina suggesting that such sunglasses are in fact not necessarily sufficient if we are to provide the ultimate protection to the retina. Retina International have issued a statement which concludes “On the basis of recent research data the scientific and medical advisory board of Retina International strongly recommends UV and Blue Blocking sunglasses for patients affected with retinal degenerations and dystrophies”. The general standard for sunglasses is that they will block out light with wavelengths shorter than 400nm. This will protect against UV but it will not exclude visible blue light. Here a protection against all wavelengths below 470nm is needed. This protection is provided by blue blocking glasses. For more information on this subject and details of Blue Bloc lenses, readers can contact Ian Pyzer on 020 8933 7914 or email [email protected]