Ask the Labs
By Joseph L. Bruneni

LEFT IN THE DARK

Q We have a patient who wears dark green glass goggles for gas welding. He now needs a bifocal. Is there a source for such an item?

--Frank Bacotti, Optical Circle, Brooklyn, N.Y.

A Welders shades are tough. We make them up to shade 3.0, but beyond that, spectacle style blanks are not available. Didymium glass is not to be used for welding! The only didymium that can be used for welding is green didymium. It can be used only for gas welding on aluminum. Forge welding (blacksmithing) is different. Didymium, or didymium combined with an IR filter (Aura Lens' AGW-186 filter) is the recommended filter for forge welding. The biggest problem is that the welding shades are designed to be dark. In the higher shades, 8 and up, they are virtually opaque. The glass contains high amounts of iron, which is the main filtration element. Currently, in shades 4.0 and higher (up to 16), the only glass that is available is flat plate, either float glass or rolled glass. No spectacle blanks are manufactured. We recommend that patients stick with the approved helmets or goggles. They are safer in the long run.

Interestingly enough, it is only part time or hobbyist welders who seem to ask for prescription spectacle welding filters--professional welders rarely make this request. Under no circumstances can our glassworking filters be used for welding.

--Mike Aurelius, president, Aura Lens Products, Inc.

STICK TO THE FACTS

Q Our office sells sunglasses and scuba masks with Rx lenses, but it is not always feasible for the patient to spend so much. We've heard of a type of "stick-on lens" that can be adhered to a goggle. How and where can we get them?

A These are one of the industry's best-kept secrets. These ultra-thin, flexible Fresnel lenses are designed for functions such as pre- and post-operative trial fittings, inexpensive vision therapy during power changes, and instant corrections on sports goggles and sunglasses. The lenses, made of polyvinyl chloride, are available in 1.00D to 40.00D prisms, plus powers up to 16.00D, minus powers to 14.00D, and D-25 segs to +6.00D. They are called 3M Press-On™ Optics and distributed by Signet Armorlite. They can be ordered from most laboratories. Signet Armorlite has a pamphlet explaining the sports applications. Ask for Swim/Ski/ Dive Patient Pamphlet No. 0103480554.

Remembering Problems From The Past

Q We've been reading the news stories about the newest lenses made from Trivex. We understand both Younger and Hoya are producing these lenses. They sound like something we should consider using, but we remember all the problems we had when we first started edging polycarbonate lenses. Even some of the new high index materials have presented problems. What kind of problems can we anticipate with this new material?

--Curious in Yonkers, N.Y.

A This new material went through years of research before the lenses were released to the trade. The easiest way to approach edging Trivex is to edge the lenses the same way you do polycarbonate. Router edgers work well and conventional wheel edgers that can be used for poly also work well. If, while using a wheel edger, you encounter smoke or haze coming from the wheel, it indicates the diamond surface is not aggressive enough for poly or Trivex. If you are able to edge polycarbonate on your edger, edging Trivex should be no problem. You'll find additional information on this subject at our Website, www.youngeroptics.com, as well as direct links to contact sources for most major edger manufacturers.

--Bill Cooper, manager professional relations, Younger Optics

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.