Ask the Labs
By Joseph L. Bruneni

PROBLEMS WITH TITANIUM FRAMES

Q I have more trouble with eyewire screws that are used with titanium frames. The screws bind often. What can be done to make these screws turn easier?

A If you are threading a titanium screw into a titanium frame and the screw "cross threads," it will bind and become stubborn. When this happens with other frame materials, either the screw thread or the hardware threads will give slightly to allow insertion.

Titanium, a strong and hard material, will not give easily. Step one: Once the screw binds, do not force it! Back the screw out and try again. The threads may match more evenly the second time.

Step two: If the screw continues to bind, place a drop of cutting oil into the hardware. That will help lubricate the threads. If no cutting oil is available, three-in-one or sewing machine oil will also help.

Usually, however, I find cutting oil to be the best lubricant for spring hinges, tapping, and general lubrication needs.

VIVA LA DIFFERENCE

Q I'm familiar with Transitions plus, Transitions III, and Transitions Xtra Active lenses. What are the differences between these and Next Generation, Velocity, Quantum, and SunSensors?

A Next Generation Transitions® Lenses are the latest 1.50 product from Transitions Optical. Next Generation is not the name of the product--it's a descriptor used to identify this technology. Transitions Lenses is the brand name and the descriptor will soon be dropped.

Transitions Plus preceded Transitions III and is no longer available. Transitions III is being phased out. Quantum was a descriptor that referred to the technology used in Transitions' high-index and polycarbonate lenses. The introduction of Next Generation Transitions completes Transitions' offering of photochromics across all designs and materials including polycarbonate, mid- and high-index, and Trivex.

We will be referring to all products as Transitions. ECPs simply need to choose the best material or design for the patient and order Transitions Lenses.

Transitions XTRActive is not a clear to dark product, but will be offered for those who prefer a tinted lens indoors. Transitions XTRActive is a lightweight alternative to glass photochromics.

Because the materials differ, there is a slight difference in performance between standard index, Spectralite Velocity Transitions from SOLA, other mid- and high-index or polycarbonate products.

Corning Ophthalmic produces SunSensors™ mid-index lenses. Like the glass photochromic products, this plastic photochromic is produced using in-mass technology.

--P.J. Downes, director of ECP and lab sales, Transitions Optical

Mirrors on Polarized Poly

Q Can a bi-gradient coating be applied to prescription, polarized polycarbonate lenses (1mm or aspheric)? Maui Jim (Titanium Sport models) does bi-gradient coating on non-prescription lenses (polarized polycarbonate).

--George Brewster

A I assume your reader is referring to a double gradient like a Vuarnet style. We have done these since the beginning of time. Coating prescription polarized polycarbonate is no problem. The only caveat is that the lens must have enough height. Typically this would be at least 21mm ("B" dimension in boxing system). Generally, the clear center is about 5mm vertically. The gradient mirrored portion on the top and bottom should extend to the edge. For practical use, there should be at least 8mm of top mirrored gradient and 8mm for the bottom gradient. Lenses shorter vertically than 21mm need to be evaluated on a case-by-case basis.

--Edwin Ellefsen, Opticote, Inc.

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.