EYE ON EQUIPMENT
Small-sized PALs for Small-sized Customers
By Susan P. Tarrant

Of course, children�s frames present certain edging challenges. Progressive lenses present certain edging challenges. When put together in one job, it can seem overwhelming.

But it�s not. Those are jobs that merely need some extra care. We asked some edging experts what they find to be the most challenging aspects of working with childrren�s PALs, and here are the tips they offered.

Can It Be Done?

PROBLEM: Is it even possible to process children�s progressive lenses? How do we do it well?

SOLUTION: PALs for children present the same challenges as narrow �B� dimension frames for adults. The issue is whether the bifocal can be fully used. Most progressives need 16mm to go from distance vision to full reading. If the frame is very small or has a �B� of less than 30mm, then it is very difficult to give them either enough distance or enough reading for them to successfully wear these lenses.

There are some progressives on the market today that are geared toward the narrow �B� frames. They offer some relief to the problem. They go from distance to full reading in as little as 12mm-13 mm. This can be a viable option. The real key to any patient using small frames with progressive lenses is to make sure they have at least 10mm-12mm of distance vision available and 4mm-5 mm below full reading to the bottom of the frame to allow complete use of the bifocal.

As far as edging these lenses, there is no difference in edging them as opposed to any other progressive.  The real key is in the choice of frame and the fitting.

�Stuart Watson, director of training, National Optronics

First Time Counts

PROBLEM: I need to improve my first-fit accuracy rate when processing small PALs.

SOLUTION:  To improve accuracy when processing PALs for small frames, use a blocking system that lets you verify size by placing the uncut lens over an outline of the frame size projected on an LCD screen.

Some edging systems provide an on-screen fitting cross when you enter the PDs and height, so you can superimpose the fitting cross on the lens over the fitting cross on the screen. With on-screen imaging, you can also verify exactly where the reading area will fall within the small frame and make adjustments before edging to avoid spoilage.

You can improve edging accuracy by using an edger with a �fragile lens� feature that automatically controls torque on the lens during processing. An edger that modulates lens clamping pressure and speed for fragile lenses or difficult sizing can significantly reduce cracking and spoilage when edging to small sizes.

�Rob Greco, Metro New York sales manager, Briot

Managing Thickness

PROBLEM: Because of the smaller measurements, the center thickness is more than it is in larger PALS.

SOLUTION: The key to keeping the center thickness as thin as possible in small PALs is to trace the frame in advance of surfacing the lens. Normally, a progressive is thicker in the center than on the edges, but tracing the frame before the processing begins means that you can crib and set your calculations accordingly, and you can optimize the center thickness. The end benefit to the patient is a thinner, lighter, more cosmetically appealing lens.

�Todd Rhodes, group product manager, Gerber Coburn

Progressive Marks

PROBLEM: We have a hard time fitting all of the parts of the progressive into those small frames.

SOLUTION: Several manufacturers offer progressives with very short channels. If this still doesn�t solve the problem, here�s another idea. Add a diopter to the add power. In the small children�s frames, the near portion will often times be cut off during edging, but adding a diopter to the add power will allow the wearer to utilize the intermediate portion as the near portion. It�s certainly not the best way to work, as it narrows the channel, but it�s a way around the problem.

Most edgers will handle decentration automatically, and all a dispenser needs to do is block on the fitting cross. But this poses a problem�the edger won�t be able to cut it out because of the decentration necessary. In this case, all a dispenser needs to do is block the lens in the passive mode�that is, the operator during layout does the decentration manually�and block on geometric center.

�Franco Aluigi, national product manager, Santinelli International