ask the labs
Troubleshooting Tips
Lens Misconceptions, Part II
Karlen McLean, ABOC, NCLC
In Lens Misconceptions, Part 1, featured in our March issue, we addressed common misconceptions about 1.70, 1.67, and lens thickness/thinness.
This month, in Part II, lab experts answer questions concerning polycarbonate, 1.60, and glass.
PREMIUM POLY
Q Polycarbonate seems to be considered a commodity product now. Is there anything that can make a standard poly a premium poly?
A In general, poly demands a slight premium over plastic 1.50, but that's about it. It is a valuable material—thin, light, and safe—with fair optics. It does, however, hate keytones (e.g., acetone).
Poly polarized works great in wrap frames, and the low Abbe value doesn't seem to be as much of an issue in bright light conditions. There's definitely a quality difference between manufacturers' poly products, but unlike high-index where the index is only part of the equation, poly is quite simply poly, all with the same Abbe value.
—Paul Zito, president, Encore Optics, LLC, South Windsor, Conn.
GLASS NOT PASSÉ
Q Are glass lenses even viable in today's optical marketplace?
A Due to the superior visual acuity of crown glass, it is used predominantly in high-quality scopes, binoculars, microscopes, slit lamps, and phoropters. Crown glass still has its place, albeit small, in our industry, mostly from a safety/occupational point of view.
Those involved in farming and other agri-businesses continue to see the benefits of glass because of their high dirt, dust, and gritty environments. In addition, glass is also the only acceptable product for infrared protection glasses in cases of welders' brazing applications.
Lastly, glass lenses are excellent for those in trades such as carpentry, electrical, automotive, plumbing, airline pilots, etc., where double-D and quadrafocal lenses are needed for optimized vision at a shorter distance, especially where overhead and instrument gauge reading is critical because of the virtually unlimited availability of add power and width in the crown glass category.
—Craig Giles, executive vice president, Soderberg Ophthalmic Services, St. Paul, Minn.
| 1.60 Classification |
|---|
| Q Is 1.60 classified as a mid-index or high-index lens? What attributes place 1.60 in whichever category it should be? A The 1.60 index has always been classified as a high-index lens by vendors. Some vendors will even classify a 1.56 or 1.54 index lens as high-index. When 1.60 came out years ago, there were no 1.67 lenses on the market to speak of, and 1.56 was the early standard for high-index. So it just made sense to put 1.60 index lenses in the high-index category. At the same time, the 1.56 high-index was reclassified or generally reassigned under the mid-index category. —Robertson Optical Laboratories, Atlanta and Columbia, S.C. |
If you have a question you'd like to have answered in Ask the Labs, send it to Karlen McLean. Email: Karlen.Mclean@WoltersKluwer.com or post it on our Facebook wall at Facebook.com/EyecareBusiness. An archive of past Ask the Labs columns can be found at EyecareBusiness.com.
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