ASK THE LABS
By Joseph L Bruneni

Keeping Up with Europe

Q We have been dispensing the new atoric progressive lenses and find they seem to work very well. We order them from a local laboratory but they tell us the lenses must be processed in Europe. Our lab tells us no U.S. labs can surface atoric lenses. Why are U.S. labs so far behind Europe on this new technology?

A We're not as primitive as you may think. Consider what atoric curves represent. They are always found on the backside of the lens. Both back curves (base curve and cross curve) are aspherized in atoric lenses, producing precise corrected vision for cylinder corrections, particularly when wearers look away from the optical center of the lens. 

Very recently, advanced generators (the machines labs use to grind the back side of lenses) became available that enable labs to surface atoric curves. Some U.S. labs are currently installing these clever machines. The same machine can even produce the very complex curves found in progressive lenses.

That only leaves one problem. The extremely sophisticated equipment required to polish atoric surfaces is only found in large factory labs based in Europe. Atoric polishing equipment for U.S. labs is expected within one to two years. This new technology will advance the type of lenses laboratories will be able to produce. Once the polishing equipment is available, it is being predicted that labs will eventually inventory "hockey puck" slabs of plastic and produce just about any type of lens ordered, including the most advanced progressive designs. By that time, labs in this country will certainly be able to produce anything you want-and that time is not far away.

Doing the Twist

Q In the past three months we have been having problems edging poly lenses. They are averaging eight degrees off axis. We had many parts replaced and the problem still exists. It is only happening to poly and mostly when small chucks are used. 

-Michelle, Town Square Optics

A This problem is due to axis flex. This is either flex in the tape and block or mechanical lens drive flex. The flex can be caused by the lens twisting off axis slightly while cutting but it bounces back and appears to be on axis upon completion. Depending on the material being cut, the condition of the diamond, the stability of the edger design, and the tape/block combination, the degree of the problem can vary. Some edger manufacturers recognize this problem and have incorporated two axis adjustments; one for CR 39 and one for poly. The fact that you are having a problem with poly while using small chucks points right to it.

-Keith Kerslake, Optic Owl

Poly with Melanin?

Q Are polycarbonate lenses ever made with melanin as a coloring pigment? If yes, who makes them and if not, why not? Is this a well-known feasible process?

-Adil Haseeb

A In the late 1980s, a front page Wall Street Journal article told how melanin protected eyes from High Energy Visible (HEV) light. The article led Bausch & Lomb to produce Ray Ban Melanin sunglasses and the Swiss government to begin issuing melanin sunglasses to its army personnel. 

Recently, research at the South Pole shows melanin sunglasses solve a serious eye problem caused by harsh light conditions there. As a result, melanin sun lenses have been in the news. Jim Gallas, the original inventor of melanin sun lenses, is president of Photoprotective Technologies, the company that owns the melanin patents. He reports that polycarbonate melanin lenses will be available in 2002. For additional information on these interesting lenses, visit www.melaninproducts.com.