The Eyes Have It
When it comes time to pick a new pair of sunglasses, an optometrist who’s done a leg or two offshore can help us cut through the glare. "Gear Roundup" from our June 2012 issue.
Sunglass-seeking sailors ask a lot of questions, and optometrist Robert Child, O.D., has the answers.
Child knows eyes: A primary-care optometrist since 1978, he has a special interest in contact lenses and the treatment of eye trauma and disease.
He also knows boats: He fell in love with a Hobie Cat when he was a cash-strapped graduate, and he’s never looked back. He and his wife own Taviawk, a Lagoon 380 cat, and they’ve also chartered extensively.
And Child knows quite a bit about blue water: His sailing résumé includes crewing aboard BG Spirit in the 2004-2005 Global Challenge.
Child also realizes that marketing can go only so far toward helping us make the right choice, and that while any decent pair of sailing sunglasses is polarized and offers protection from ultraviolet rays, there’s more to it than that. That’s why I went to him with a list of questions when the newest models for the spring and summer of 2012 started rolling in.
Q: When it comes to sunglass lenses, how do plastics/polycarbonates and glass compare?
A: Traditional plastic (CR-39) has excellent optical qualities, is lighter than glass, and is readily tinted, but it scratches easily. Polycarbonate is a more dense plastic, so it can yield a thinner lens that’s virtually unbreakable. Its optical characteristics may not be as good because of chromatic aberrations. It does scratch easily and is more difficult to tint than CR-39. To compensate, makers today coat virtually all plastic-type lenses to make them resistant to scratches.
Glass has excellent optical characteristics and is quite scratch resistant, but it’s heavy. Especially significant for sailors, it’s not as impact resistant as the plastics, despite chemical tempering. It doesn’t accept a surface tint well, so manufacturers put the tint in the glass rather than on it.
When sunglass makers advertise that they’ve fused the best properties of plastic and glass, the material may be a newer type of plastic that’s the lightest available, is dense for thinner lenses, yet still has excellent optical quality, tints easily, absorbs 100 percent of ultraviolet rays, and is very strong, probably the best for drilling frame mounts.
Q: What does polarization mean? What does protection from ultraviolet rays mean? What’s the difference, and why are these factors important for sailors to consider?
A: Polarization filters visible light so we have less reflected glare and feel visually more comfortable, whereas protection from invisible ultraviolet light is important to keep our eyes safe from high-energy radiation. In polarization, a membrane blocks light reflected from a horizontal surface, such as water, sand, or snow. Fundamentally, ultraviolet protection is important to sailors because we’re in the sun a lot, and the high energy of ultraviolet radiation can cause damage to our skin and eyes. Children are subject to the same hazards as adults and should have their eyes protected as well.
