$50 for $150 Toward Prescription Glasses and Sunglasses at Bob Keathley Opticians

Bob Keathley Opticians

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What You'll Get


The Deal

  • $50 for $150 toward prescriptions glasses and sunglasses

Polarized Lenses: Blocking the Glare

The inventory includes sunglasses with polarized lenses. Learn exactly what that means with Groupon’s introduction to this technology.

When light leaves the sun, it’s kind of aimless. As a ray barrels through space at the speed of, well, light, the advancing electromagnetic field that makes up a light wave fluctuates in strength around the direction of the ray in many different planes.

It’s the job of polarized lenses to get this erratic light in line. A polarizing filter consists of microscopic crystals in which strands of molecules are all aligned parallel to each other. When unpolarized light hits the filter, those molecule chains absorb any energy that’s traveling in the same plane they’re aligned in, blocking it from passing through. What emerges on the other side is now polarized, with all its energy fluctuating within a single plane.

Why worry about how a wave of light gets to you at all? As anyone who’s ever squinted through the too-bright reflection from a car’s hood or a body of water can sense, light polarized in certain directions can be dangerous. When light bounces off horizontal surfaces, it becomes horizontally polarized, resulting in the blinding phenomenon known as glare. For this reason, sunglasses with polarized lenses are coated with (or, in some cases, formulated containing) a filter that blocks this horizontal light, allowing through only the gentler vertical components in the environment. This improves safety for drivers, beachgoers, boaters, and whale ranchers, although not for downhill skiers—on the slopes, you need to see horizontally reflected light to alert you to icy patches ahead.

The Fine Print


Promotional value expires 120 days after purchase. Amount paid never expires. Not valid with insurance. Merchant's standard cancellation policy applies (any fees not to exceed Groupon price). Limit 1 per person, may buy 1 additional as gift. Limit 1 per visit. Valid only for option purchased. All goods or services must be used by the same person. Not valid in combination with other promotions Merchant is solely responsible to purchasers for the care and quality of the advertised goods and services.

About Bob Keathley Opticians


By purchasing this deal you'll unlock points which can be spent on discounts and rewards. Every 5,000 points can be redeemed for $5 Off your next purchase.