Ask The Labs
By Joseph L. Bruneni

HELP FOR MATURE EYES

Q I often have difficulty reading the identification markings on progressives. I remember years ago when Modern Optics promoted the use of a high intensity arc lamp to inspect lenses. The lamps were expensive, but I suspect they would aid in reading those engraved marks. Are there suggested ways to make out these markings?

A Progressive addition lenses (PALs) are identified by manufacturers' laser engravings and provide manufacturer identification, add power, lens material, and lens brand. The engravings are not always easy to find, especially if lenses have an anti-reflective coating, are tinted, or are older or scratched, especially so for presbyopes or inexperienced persons. It is even worse in dim lighting, as in the exam room. An instrument called Progressive Addition Lens Identifier (PAL ID) provides a clear view of the engravings. It consists of two high-powered fluorescent tubes illuminating a magnifying lens with a polarizing filter. Holding the lenses between the light and the magnifier makes it possible to see even the faintest of marks in any ambient lighting situation. Comparing the marks to an OLA progressive lens guide identifies the lens. For additional information on the PAL ID, go to http://pal-id.com or contact Essilor Ophthalmic Instruments (888-202-4906).

--Danne Ventura, director, professional relations, Essilor USA

SEEING CLEARLY

Q Does anyone make a clear polarized lens? We think that such a lens might help older persons when driving at night.

A Your idea of polarized lenses for night driving is interesting and has some historic significance. When Edwin Land invented polarizing film in the 1930s, his original concept was to incorporate the film in automobile windshields and headlights to aid driving at night. Car manufacturers nixed the idea because of cost. Land's idea wouldn't have worked anyway because, as polarized manufacturer Eric Lindquist of Specialty Lens Corporation points out, the amount of glare reduction provided by a polarized lens is inversely related to the amount of light it transmits. Conventional gray C polarized lenses transmit 15 percent of light and almost totally block reflected glare. Yellow polarized lenses transmit 85 percent of light, but can only block 12 percent of unwanted glare. Imagine making Venetian blinds out of clear plastic slats. Close the blinds and light would still pass through. This factor would have doomed Land's polarized windshield idea even if auto manufacturers had been willing to pay for it.

When words fail

Q Is there an index of common terms for the eyeglass trade which would include, for example, rim, rimless, rim lock, temple?

--Reader Dave

A There is an excellent source that covers most of what you asked about. It is the Dictionary of Ophthalmic Optics, published by the National Academy of Opticianry. It can be ordered from the organization's Website, www.nao.org, or by calling 800-229-4828. The term "rim lock" is not listed in the dictionary. I suspect it is a trade name like "rimlon" and would not be included.

If you have a question you'd like to have answered in Ask the Labs, send it to Joseph L. Bruneni. Fax: 310-533-8165. Phone: 310-533-4975. E-mail: joe@bruneni.com.  Or mail questions to: Vision Consultants, 2908 Oregon Court, #I-2, Torrance, CA 90503. An archive of past Ask the Labs columns can be found on the Eyecare Business Website at www.eyecarebiz.com.