hands on - ask the labs
Q&A
by Karlen McLean, ABOC, NCLC

ROUGH ON RIMLESS

Q: A majority of our patients are 50 to 90 years old. They want rimless frames, but they're often rough on their glasses, and some aren't good candidates for PALs. How can we get them into rimless?

A: Poly, a solution for higher-index and impact resistance, has some drawbacks. First, it's tough to get good knife-edges on poly for high plus Rxs. Second, some patients report light fringes and reflections. Third, drill holes can develop fractures, screws work loose or break out, lenses can become loose in the frame, and fitting adjustments can be compromised.

Trivex is perhaps a better lens solution here. Lenses can be made thinner with a knife-edge on plus lenses, yet are impact resistant and durable. Lens fractures and splitting at drill holes are virtually eliminated, and screws can be tightened down until the lenses are good and tight.

Patients are likely to have less trouble with scattered light, considering higher Abbe value. Traditional trifocal design is available in Trivex, for example.

—John Miller, vice president sales, X-Cel Optical Company, Sauk Rapids, Minn.

ODD OC'S

Q: It seems to me that a patient with a significant difference in power between the two eyes who is buying single vision lenses should have the optical center measured and specified, just like we do with aspheric lenses. It also seems that such a patient would benefit more from aspheric lenses than most people. Can someone tell me if I'm right or not and the reasons why or why not?

A: The answer to the first part of your question is yes. We just had a situation with a customer who had a patient with the same issue. His Rx was OD -6.50; OS
-1.50. Specified optical center on the right eye was 1.5 and specified OC on the left eye was 3.0.

In doing this, we gave the patient a pair of lenses that were cosmetically balanced. As for aspheric lenses, yes, they're highly recommended, again for cosmetic reasons; aspheric lenses are flatter.

However, the material we chose in this case was polycarbonate with AR. Either 1.67 or 1.71 high index lenses would be great as well.

—Mike Francesconi, vice president, Katz & Klein, Inc. Optical Laboratory, Sacramento, Calif.

AR & Alcohol

Q: I've heard it's not safe to use alcohol-based cleaners on AR. However, it seems like many people do with no problem. What's up with that?

A: There should be no problem caused by using alcohol-based cleaners on AR lenses. If an AR coating has a major problem to begin with, then soaking it in alcohol will cause that problem to show up in an accelerated fashion...but people typically don't soak their lenses in alcohol. On the other hand, consumers should avoid using caustic cleaners, like ones with ammonia, on AR lenses.

—Larry Clarke, president and CEO, Satisloh North America, Inc., Germantown, Wisc

If you have a question you'd like to have answered in Ask the Labs, send it to Karlen McLean. E-mail: mcleank@lwwvisioncare.com or fax: 215-643-1705.