SUNGLASS UV Radiation Guide

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     Ultraviolet Rays are rays that reach earth from the sun that are too high in frequency for the human eye to see

   The reason Ultraviolet rays are not visible is that the human eye can only see between 400 Nanometres and around 800 Nanometres.

   Nanometres (Nm) are the unit of measurement for light rays. The different rays are interpreted by our eyes as different colours. Blue, for example is a high frequency light wave (400-450 Nm) and Red is a very low frequency light wave (around 750Nm).

   So high frequency ultraviolet rays arrive on planet earth between 0 and 400 Nanometres. 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 are by staying in a shaded area or by using sunglasses which block all UV Rays.

   There are three types of UV Rays:

1. UVC--between 0 and 250 Nanometres--these harmful rays are fortunately almost entirely blocked out by the Earths atmosphere.

2. UVB--between 250--360 Nanometres--THE BIG BADDY! These are the most harmful UV Rays are are responsible for most damage done to human eyes. These insidious ultraviolet rays pass right through Earths atmosphere and bore directly into the deep internal workings of the human eye.

3. UVA--between 260--400 Nanometres--less harmful than UVB rays but still of some concern. These rays are only blocked by lenses which block out all light up to 400 Nanometres. (Called UV400 lenses).

   INFRARED RAYS are slower, lazy waves which cannot penetrate the human eye. They simply bounce off the surface and may be noticed, if at all, as making the eye slightly warmer than would otherwise be the case.

   Before buying sunglasses it is useful to check that the brand you are buying uses UV400 lenses.

   It is helpful in summer climates to consider some side protection as “stray light” can enter via the side on smaller lens sunglass styles. This is particularly true when skiing or boating where UV light reflects off the surface of snow and water and enters the eye via the “side door” if it has the chance to do so. Recent wrap-around styles popular today are useful because they eliminate most stray light.

THE HIGH RISK CHECK LIST:
You are at a higher risk of sun related eye problems if you...
     • Partake in outdoor sports.
     • Work outdoors, or with artificial light sources.
     • Live in a bright, sunny climate.
     • Have had cataract surgery.
     • Take photosensitive prescription medicine (antibiotics, hypertensive medicine, tranquilizers, oral contraceptives, etc.).
     • Have been exposed to bright sunlight since childhood.
     • Wear contact lenses.