CUTTING UP
by Karlen McLean, ABOC, NCLC

Q: What's the best way to cut polycarbonate lenses—wet, dry, or a combination? And, while you're at it, what's the best way to cut Trivex lenses?

A: We find that we get the best results by rough cutting poly dry and bevel cutting poly wet. This minimizes swarf, keeps the lens and edge clean, and keeps the equipment clean.

With Trivex, we get the best results by dry cutting the entire job, unless there's an edge polish. For edge-polishing jobs, we use a wet cycle on the finish. Otherwise,
residual heat can cause pressure
on the lenses and the waste material can gum up the wheels.

Usually, we try to batch cut Trivex lenses that require polishing so we can clean the unit afterward.

These procedures reflect most lab set-ups today; the investment in modern equipment technology is well worth it. We also have a full-time maintenance staff to help keep our operations smooth.

Keith Cross,
VicePresident,
Northeast Lens Corp.,
Newton Upper Falls, Mass.

SUPERHERO EYES

Q: What lens material and designs are best suited for X-ray and laser technicians?

A: In both cases, the lenses require specialized processing.

We fabricate lenses for X-ray techs in single-vision, flattop 28, or PAL designs; the material must be specially-tempered 1.8 leaded glass.

Laser lenses are highly task
specific. The laser technician must know the power output of the laser device or devices they use and be able to verify this before lenses are made.

Power output can vary depending on the laser equipment and application, whether industrial, medical, design, or other application.

Most often, we find that specially designed protective face shields are far more commonly used than eyewear for laser protection.

— Jeff Szymanski,
Sales Manager,
Toledo Optical Laboratory, Toledo, Ohio

ASK THE LABS

If you have a question you'd like to have answered in Ask the Labs, send it to senior editor Karlen McLean. Fax: 215-643-1705. E-mail: mcleank@LWWVisionCare.com. An archive of past Ask the Labs columns can be found on the Eyecare Business Website at http://www.eyecarebusiness.com.

Slab-Off

Q: What's the difference between conventional slab-off prism and reverse slab-off. Also, in what situations would you suggest that it's appropriate to use slab-off?

A: Conventional slab-off is grinding base up prism on the lens with the most minus or least plus. Reverse slab-off is front-side, mold-in with base down prism on the lens with the least minus or most plus. A conventional slab-off offers a thinner choice with less magnification. Slab-off corrects for vertical imbalance, which is measured in prism diopters. Usually, if the prescription has a 2.00D difference between eyes, slab-off prism is recommended. Some doctors prescribe slab-offs to 1.00D imbalance between both eyes, depending on the patient's needs.

— John Haskins,
president,
Slabs Plus, Ruskin, Fla.