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Sat 30 Jan, 2016 05:54 pm
I believe certain types of eyeglass lenses block visible (or ROYGBIV) light. Such glasses look dark to us because the lens blocks the ambient visible light. Similarly, if we look through these glasses, the thing we look at looks dark, for the same reason.
When the eye (or brain) detects that little visible light is reaching the eye, it widens the pupil, potentially increasing the amount of UV light reaching the inner eye.
If the eyeglass lenses also block a (hopefully high) percentage of UV A and UV B, then the lenses would partially or totally or more than totally compensate for the increased exposure of UV radiation brought on by the widened pupils.
Accordingly, why don't eyeglass manufacturers produce an eyeglass lens that blocks UV light without blocking visible light?
@gollum,
What would be the purpose? You don't need them inside and outside it doesn't help you if you are protected against UV but blinded by visible light.
@engineer,
I don't understand the question. My eye lenses have had a uv protective coating on them for decades, from whatever optometrists. I'm near sighted and don't really need glasses much in my small townhouse, but I need them to see in the distance outside. If I take my glasses off outside, the light doesn't noticibly change; only thing that happens is I can't see far away and not so well in the mid range. I happen to wear trifocals, famously hard to get used to, which has nothing to do with UV coating. Maybe I'm not understanding about the diff types of UV.
The coating I have is the one that my ophthalmologist says I need.
@gollum,
I have safety glasses in both clear and tinted, and they both claim to block something on the order of 98% of ultraviolet. I suspect that's common as these are very inexpensive glasses.
I would give the brand, but I can't make it out on the frames
@engineer,
engineer wrote:
What would be the purpose? You don't need them inside and outside it doesn't help you if you are protected against UV but blinded by visible light.
I use clear or very lightly tinted glasses on the bicycle, mostly for protection against insects and blowing dust. Where I ride, there are sudden transitions from full sunlight to dark shade and with a dark lens I can't tell potholes from patches of dark shade. The uv protection is almost a side issue.
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