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Rudi Kiefer: Filters are something to look out for when buying sunglasses
Rudi Kiefer
Sunglasses are probably more useful right now than in the summer. The sun doesn’t come up high in the sky. Trips from Gainesville to Atlanta during late afternoon are challenging because the road goes toward the southwest. That’s straight against the low sun, with a great deal of glare limiting vision.

Cheap models help some, but higher-priced polarized ones provide a sharper image.  That’s because polarization removes some of the glare from non-metallic reflective surfaces.

Photographers often use a polarizing filter, avoiding all that stray light bouncing off tree leaves, stone walls and tiny droplets of water in the air.  What helps produce picture-postcard landscape colors is also helpful in enhancing drivers’ vision.  

When we’re not behind a glass surface, like a window or a windshield, it’s important to use glasses that filter out the ultraviolet, or “UV”, portion of the light. Ultraviolet is the shortest wavelength in the electromagnetic spectrum. It’s invisible to the human eye but causes damage to the retina.

The retina is the surface where the image forms. Up front is the lens.  In that foremost part of the eye, cataracts are common with advancing age, causing cloudiness in the lens and a “foggy” vision effect. Besides age and diabetes, excessive sunlight has been named as a factor in cataract formation.

The good news is that Gainesville is home to several excellent eye centers, offering laser surgery (not to be confused with Lasik vision correction) that replaces the lens.

I can attest to the marvelous vision improvement after the brief laser procedure done right here in Hall County.

If you’re driving during daytime, and things still look foggy, it’s probably due to the atmosphere.

I like to wear orange-colored sunglasses during bright daytime fog. This color filters the bouncy blue wavelengths out and makes some of the fog disappear. Obviously, this isn’t appropriate at night.

Photochromic sunglasses are popular.  They darken in bright light and brighten in the shade.  

But they do this through a chemical reaction in the silver chloride contained in the lens, which requires UV light to activate.

Modern car windshields have UV filters built in, so don’t be surprised if those expensive photochromic glasses don’t seem to work in the car.  On a motorcycle, they work but should be shatterproof. I’ve had the best results with impact-proof shop glasses of the major brands.

Rudi Kiefer, Ph.D., is a professor at Brenau University, teaching physical and health sciences on Brenau’s Georgia campuses and in China. His column appears Sundays and at gainesvilletimes.com.

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