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10

Polarization and UV protection on sunglasses are two different things. While UV refers to light of a wavelength of approximately 10nm to 400nm, light of any wavelength can be polarized. Sunglasses with a polarization filter block light, that is horizontally polarized (e.g. light reflected on water). This has no specific effect on UV-light. So polarized ...


9

The problem is that eyeglass prescriptions are calculated for a standard distance between the lens and the eye, with the lenses in flat frames parallel to the face. You can see the effect of varying lens-to-eye distance simply by pushing or pulling on your conventional eyeglasses, and the effect of angle by tilting them on the bridge of your nose. Your ...


9

Background Due to the very nature of light and lenses it is impossible to not have depth perception change when looking through a lens. The light will pass through the first surface of the lens, slow down (plastic is denser than air), hit the principle axis and then exit the second surface of the lens and converge at the focal point. What you are seeing ...


7

Those types of glasses do not provide adequate protection from sunlight, especially in areas with lots of reflective surfaces (desert, snow) and at high elevations where there's more UV radiation due to the thinner atmosphere above you. What you want are either wrap-around glasses which don't let light in the sides, or particular glasses called "glacier ...


6

These are generally known as glacier glasses. They are rated as Category 4 on the CE scale and you aren't supposed to drive while wearing them. Sunglasses in Category 4 only transmit 4-8% of available visible light. Hidalogos sunglass guide has a very complete list of the different factors in choosing sunglasses. Category 4 come in a wider range of ...


4

One of the classic applications of polarized sunglasses is to skiing. Light from the sun is unpolarized, but when it is reflected from a surface at a glancing angle, it becomes highly polarized. When you're on a snow field, a lot of the bright light getting into your eyes is light reflected from the snow, and when the sun is low in the sky, this glare is ...


3

Paul and Kevin are correct here - any corrective lens has to alter what your eye sees. Your brain very rapidly corrects (a few minutes) but it is a basic function of optical physics that is unavoidable. It's not because of two layers of glass, it is the correction process - you are changing the light path. I would suggest that if you need the corrective ...


2

The basic idea of polarizing glasses is not to block all light, it's to block light that undergoes a glancing reflection, such as sunlight coming to your eye off of water or snow from near the horizon. The initially unpolarized light becomes highly polarized by this type of reflection, so by eliminating it, you make it easier to see and be comfortable ...


2

Those large sun glasses that are used after cataract surgery are great - stops 100% of all types of uv and completely covers your eyes. New $70, used $5 at charity store or just take your mums. Yes, you will look like an old person and they are breakable plastic, but for $5, buy 2.


2

There are actual standards for this. If you are going somewhere where snow blindness is a real possibility, you should have sunglasses that meet the standard. The most common standard used in outdoor sunglasses is the Category standard based on the european CE standards. There are 5 categories 0-4 This page has a good overview. ...



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