We were having a discussion at our office concerning poly lenses. Do clear poly lenses block UVA and UVB?
We were having a discussion at our office concerning poly lenses. Do clear poly lenses block UVA and UVB?
UVA 400 nm - 320 nm
UVB 320 nm - 290 nm
UVC 290 nm - 100 nm
High intensities of UVB light are hazardous to the eyes, and exposure can cause welder's flash (photokeratitis or arc eye) and may lead to cataracts, pterygium,[30][31] and pinguecula formation.
UV light is absorbed by molecules known as chromophores, which are present in the eye cells and tissues. Chromophores absorb light energy from the various wavelengths at different rates - a pattern known as absorption spectrum. If too much UV light is absorbed, eye structures such as the cornea, the lens and the retina can be damaged.
Protective eyewear is beneficial to those who are working with or those who might be exposed to ultraviolet radiation, particularly short wave UV. Given that light may reach the eye from the sides, full coverage eye protection is usually warranted if there is an increased risk of exposure, as in high altitude mountaineering. Mountaineers are exposed to higher than ordinary levels of UV radiation, both because there is less atmospheric filtering and because of reflection from snow and ice.
Ordinary, untreated eyeglasses give some protection. Most plastic lenses give more protection than glass lenses, because, as noted above, glass is transparent to UVA and the common acrylic plastic used for lenses is less so. Some plastic lens materials, such as polycarbonate, inherently block most UV. There are protective treatments available for eyeglass lenses that need it, which will give better protection. But even a treatment that completely blocks UV will not protect the eye from light that arrives around the lens.
http://en.wikipedia.org/wiki/Ultraviolet
It is estimated that this year in Canada there will be 3,150 new cases of
malignant melanoma, the deadliest type of skin cancer, and 64,000 new cases of
non-melanoma skin cancer (NCIC 1998). Between 1986 and 1995 the age standarized
mortality of malignant melanoma increased by an annual average of
2.7% among men and 1.7% among women. This is the largest increase in
mortality of all cancer sites for men and the second largest for women, after lung
cancer. It is estimated that this year 740 Canadians, 450 males and 290
females, will die from malignant melanoma (NCIC, 1998). National organizations
such as the Canadian Cancer Society, the Canadian Dermatology Association,
the Canadian Radiation Protection Association (CRPA, 1999), Health Canada,
the Canadian Medical Association etc. have expressed their concern about the
increase of this easily preventable cancer.
http://www.lrws.gov.sk.ca/solar-arti...olet-radiation
Thank you for your postings. If anyone can add to the discussion.........that would be great!
What is the story on UV dyes that are used in cheap drugstore sunglasses? Can these dyes rub off when cleaned?
The answer is yes and no...................................
If the lenses are polycarbonate they absorb for sure UV B and nothing can rub off as polycarbonaste has the UV absorber in the material incorporated.
If it is CR39 and has been treated with one of the 1 minute UV solutions which many labs do to save time, it will rub off in a short while.
The lens has to be under heat for at least 7 minutes in the solution to open its pores fully and let the UV material penetrate into it. Also when treating a lens, never take it out from the soution and wash it under the water tap, as the lens pores are still open and you can flush out the UV material. Always lay them on a table to cool off to room temperature before washing them.
Thanks for the reply Chris. Have you ever seen test results of a typical $10 pair of sunglasses that claim to be 100% UV protection? Do these things actually have that protection off the shelf, and does the protection last over time? A study on this would be very interesting to read.
In optical standards, UVB is defined as radiation ranging from 280 to 315 nm and UVA is defined as radiation ranging from 315 to 380 nm.
Polycarbonate absorbs 100% of UVB and 100% of UVA.
Most high-index plastics also absorb 100% of UVB and 99-100% of UVA.
Untreated hard resin (CR-39) absorbs 100% of UVB and 80-92% of UVA, depending upon the manufacturer.
And, as Chris has already pointed out, you can treat hard resin with a UV solution to provide greater absorption of UVA or blue light up to 400 nm.
Care should be taken when treating lenses that will have an AR coating applied, however, since excess UV solution can reduce adhesion in some cases.
Note that in Europe, they measure "Solar UV," which is slightly different than the figures used in the US.
Best regards,
Darryl
Darryl J. Meister, ABOM
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