Readers Respond
Regarding "A Piercing Question" (drilling poly lenses) in the last "Ask the Labs," I think that problem could be solved one of two ways, or a combination of both.

Considering that poly lenses are thin at the edges, especially in plus, it may be difficult to drill half way from each side. What I do in every case -- poly or CR 39 -- is drill the hole all the way through, not with a drill, but with a 1.5mm spherical burr from a Dremel case. The burr removes all the debris as it works. Then, using a 5-sided reamer, we enlarge the hole size to what we need. It also may help to enlarge the hole enough (with the reamer) to use one of those plastic screw sleeves we once used with glass lenses for rimway mountings.--Fernando J. Rueda, Houston

Your January installment contained an article on polycarbonate lenses and gave information on how to differentiate poly from CR 39 lenses. When we have an unknown lens material, we remove it from the frame and drop the lens, face up, a few inches onto a countertop. We find that the sound reveals the lens material. Glass has a distinct "ring," CR 39 has a kind of dull thud, and poly a much sharper thud. We keep comparison samples nearby to assist in the differentiation.--Michael W. Schwartz, O.D., Grants Pass, Ore.

Q. Rack Reading Glasses
An ophthalmologist in our town tells his older patients who only need glasses for reading to pick up a pair of readers in the drug store. We also notice more places carrying racks of reading glasses.

We've always believed readers were an inappropriate item for proper vision, but now we even see them advertised in optical magazines. Your comments, please.

A.
Interest in readers has mushroomed in the past year. A few companies have sensed a vast untapped market for readers.

Non-dispensing ophthalmologists sometimes feel they are saving their patients money by referring them to the drug store for reading glasses. Rack reading glasses, however, require certain compromises to best vision. Manufacturers compromise by using a 64mm PD for all readers, assuming this is the average. Patients with a narrower or wider PD who wear a strong add will certainly experience disturbing horizontal prism with the wrong PD. Their second assumption is that all presbyopes require the same correction for each eye. Depending on their uncorrected distance vision, this is seldom the case.

One manufacturer has introduced a line of quality readers for the optical trade that features separate lenses so dispensers can vary the PD and use different powers for each eye. The manufacturer believes that it is better for consumers to buy quality readers from an eyecare professional than from a drug store.

Q. Color Me Visually Enhanced
We're always at a loss to answer a patient's questions about which color would work best in his or her sunglasses. Are there guidelines?

A.
We included a Color Recommendations and Benefits Chart in a sunglass booklet our company publishes, titled "Pair Up." Some of the guidelines are:

• Gray. Recommended for: all-purpose sunwear, driving, sports, water activities. Benefit: natural color contrast.
• Brown. Recommended for: all-purpose sunwear, driving, sports, water activities. Benefits: filters more blue light, improves visual acuity, sharper definition on the golf links.
• Hi Contrast Amber. Recommended for: all-purpose sun lens, low light. Benefits: filters blue light, improves acuity, enhances color, and provides sharper definition on golf links.
• Yellow. Recommended for: shooting, fishing, high contrast for early and late in day, cloudy or overcast days. Benefit: improved depth perception.
• Mirrored. Recommended for: any high glare situation. Benefit: reduces absorption of near infrared rays, providing maximum glare protection under intense sunlight.--Judy Miyasaki, Kbco Polarized Lenses, Aspen, Colo.

Q. Bus Safety and Infrared
Our organization operates electric buses, and our workers, all of whom wear poly safety glasses, are exposed to flashes and sparks from the electric shoe on the top of the buses. Our concern is UV and IR protection. Do you have any advice?--Safety Director, British Columbia Transit System

A.
With polycarbonate lenses, you have no concern with UV since these lenses block 100 percent of UVA & B. In regard to infrared transmittance, the primary concern is continuous or long-term exposure where the worker is staring directly into a continuing brilliant flash, such as in welding. Polycarbonate transmits 85 percent of IR, but since your employees' IR exposure comes in random bursts or flashes (from sparks), potential eye damage from IR exposure should not be a concern. To provide total protection from infrared would require wearing a welding helmet while working on top of the bus, probably not a practical solution.--Dan Torgersen, OLA Technical Director EB

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