Protect your eyes from UV

Waimarino Bulletin, Volume 6, Issue 260, 25 October 1988, Page 7

Protect your eyes from UV

The light rays that the eyes detect fall from red rays which have very long wavelength through to violets of short wavelength. Infrared rays w e r e thought to be harmful to the eyes a few years ago. However it has since been discovered that they are not as harmful as shorter wavelength light, which contain more energy. The increased danger with short wavelength light is because the eye cannot register it as easily and adjust the pupil to cut down the light coming in. Below the visable light range are the most dangerous of all light rays - Near Ultraviolet and Ultraviolet (UV). Because the eye cannot register them at all, the pupil does not contract to limit their effects. All visable light is harmful but the scale of

the danger increases as the wavelength decreases. Normally the eye can cope with visable light because the pupil contracts to limit entry or the light is too strong and hurts the eye so you turn away. The danger is with less visable or invisable light. We do no actual harm to our eyes when we are out in in the summer sun, but skiers and mountaineers can readily develop snow blindness if they leave their eyes unprotected on sunny days, or even in whiteout conditions. The reflection of ultra-violet wavelengths from snow is typically 75 per cent -compared to a reflection of only 25 per cent from sea, and the altitude of snowfields means less atmosphere to filter the sun's rays and thus there is less absorption and scattering of ultra-

violet radiation. During the last year or so there has been an increasing amount of interest in ultraviolet absorption in eyewear lenses. Until recently it was believed that the only effects o f ultraviolet on the eye were to the anterior surface (the corneal epithellum and conjunctivia), but recent research has shown without doubt that ultraviolet has significant effects on the eye lens and retina as well. Eyewear Essential In the 1950's many different coloured glasses, s m o k e d glasses, metal coated glasses and polarised lenses were tried out in various shapes by scientists working in the Antarctic. Neutral grey lenses were preferred to glasses of any other colour. Yellow lenses are generally considered to help in misty conditions.