 The sun emits
ultraviolet radiation which is damaging to the eyes. Lenses with
ultraviolet protection prevent that harmful radiation from touching
your eyes. Polycarbonate, high index, polarized, and sun-sensitive
lenses all automatically contain UV protection. Hard resin lenses
need an additional coating to add UV protection. According to United
States Federal law, all sunglasses sold in the United States must
have UV protection. However, many low-priced sunglasses for sale
through street vendors do not comply with this rule. Using tinted
lenses without UV protection is extremely damaging to your eyes,
because the dark tint causes your pupils to dilate and increases the
surface area of your retina that can be damaged by the ultraviolet
radiation. |
Polarized lenses are used in sunglasses to reduce
glare from reflective surfaces such as the surface of water or the
hood of a car. They accomplish this through a process called
polarization, much like a venetian blind controls sunlight through a
window. Sunlight itself is not polarized - light from the sun will
either be absorbed or reflected horizontally, diagonally or
vertically. The problem this causes lies in the horizontal
reflectivity. Sunlight bouncing off a horizontal surface will strike
the viewer's eyes at a similar angle. This means the glare from the
surface of the water or the road or the car hood will be strong.
Polarized lenses have a laminated surface containing vertical
stripes. These stripes only allow vertically-polarized light to
enter the wearer's eyes. Glare is eliminated because the
horizontally-polarized lightwaves cannot bypass the polarized
filter.
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Adidas
Burberry