Ultraviolet radiation (UVR) is light emitted by the sun that reaches the earth but is too high in
frequency for the human eye to see. The human eye can only see light in the range 400Nm
(Nanometres) to around 800Nm. UVR has a wavelength of less than 400Nm.
Nanometers are the unit of measurement for the wavelength of light rays. Different wavelengths
of light are interpreted by our eyes as different colours. Blue, for example, is a high frequency
light wave (400Nm to 450Nm) whilst red is a low frequency light wave (around 750Nm).
High frequency Ultraviolet Rays arrive on earth between 100Nm to 400Nm. These high
frequency waves are piercing and powerful and are responsible for most skin cancers and sun
related eye ailments. They pierce the eye unimpeded. The only way of protecting yourself from
them is by staying out of the sun or by using sunglasses which block UV rays.
There are three types of UV rays:
UVC – (100Nm and 280Nm) – these harmful rays are fortunately almost entirely blocked out by
the earth’s atmosphere.
UVB – (280Nm and 315Nm) – these are the most harmful UV rays are responsible for most
damage to the human eye. They pass through the earth’s atmosphere and can penetrate into
the internal workings of the eye.
UVA – (315Nm to 400Nm) – these are less harmful than UVB but can still be harmful. These
rays are only blocked out by lenses which block out all wavelengths up to 400Nm (usually
described as UV400 lenses).
Before buying any sunglasses it is important to check that the brand you are purchasing uses
UV400 lenses.
It is helpful in summer climates to consider some side protection as “stray light” can enter the
eye via the side on smaller lens sunglass styles. This is particularly true when skiing, boating or
on the beach where UV rays reflect off the snow, water and sand. Wrap-around styles popular
today are useful as they eliminate most “stray light”.