Download shortened Effects of Blue Lighton RP

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]