>> ....there may be some hazard
>> to the eyes from some sources of UV.
>>
>> Does anyone know more about this??
Perhaps i am qualified to speak on this topic.
The wattage is likely to be a major factor in the potential damage from Ultra-Violet lamps, in
conjunction with the amount of UV hitting the eyes, whether directly or reflected. Wear UV absorbing
safety specs.
UV is generally categorised as UVA or UVB according to wavelength although of course it is a
continuum rather than 2 separate things, and that continuum blurs into visible blue (violet) light as the
wavelength gets longer.
The shorter the wavelength, the higher the frequency, which translates to greater tissue damage, but
short wavelengths are quickly absorbed (they don't penetrate deeply). Conversely longer, near-visible
wavelengths do less acute damage, but penetrate more deeply.
UV can cause corneal damage (the cornea is the clear front wind-screen of your eye, that people put
contact lenses on) much like sunburn on skin (same as snow-blindness, arc-eye) which can be very
painful for a few days. It is also a major reason for cataract, which is where damage to the ocular
lens inside your eye (just behind the pupil-hole in the iris) causes the lenses to become opaque. The
accumulated effect of natural sun UV is a large part of why almost everyone has cataract if they are
over 75 - farmers and beekeepers and other outdoor occupations tend to get cataract earlier than
housewives and office-workers (wear sunglasses, and a hat to shade your eyes).
UV doesn't usually penetrate further than the ocular lens. It acts as a built in UV filter,
absorbing the UV, sacrificing itself to prevent the UV reaching the delicate tissues of the retina.
Near-visible UV, and just-visible violet light, with their longer wavelengths do less damage to the
cornea and lens on the way through, but can penetrate to the retina (the light-sensitive membrane at
the back of the eye, which converts light into electrical impulses to be sent up the optic nerve to the
brain and finally 'seen' - equivalent to the film in a camera). The retina being light-sensitive is delicate,
and ophthalmologists (eye-specialist doctors) today recognise that ordinary visible blue light, being the
shortest wavelength that usually penetrates to the retina can gradually cause damage. Light intensity
(Wattage) is the major factor here (don't look at the sun).
Because of its poor penetration, UV is easily blocked with UV-absorbing specs. Sunglasses would
work, but will probably make it difficult to see the scale. Fortunately most plastics absorb UV, without
needing tinting or coating. I prefer to work my bees without a veil (unless they're beeing impolite) yet i
wear ordinary cheap plastic safety specs to guard against the slim possibility of a sting to the eyes.
These also will block UV, whether from sun or lamp. Ordinary prescription plastic spectacle lenses
also absorb UV.
UV blocking safety specs will not stop you from seeing the scale as you are seeing the re-
emitted (fluoresced) visible blue light (which passes through clear plastic), not the actual UV.
In summary: use low wattage, don't look directly at the light source, and use plastic safety lenses,
especially if there are highly reflective surfaces around. Oh and wear sunglasses whenever the day is
bright enough to use them. You may not notice the difference now, but you are likely hastening cataract
otherwise (this goes double for Aussie and Kiwi beekeepers, our sun UV levels are... astronomical).
My own query is how do the bees react to the UV lamp, given they can see these wavelengths? I'll have
to take the Burton-lamp into the hives...
-Pav (Moonlights as an Optometrist)
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