Ask the Labs
By Joseph L. Bruneni and Martine Breheny

INVENTORY BLUES

Q We keep reading about all the new automated equipment labs are installing, but sometimes we are not seeing faster delivery from labs. What's the point of automating production if it doesn't speed delivery? At one time, our lab could almost always get a rush job out in one day. More often now, it takes two or three days. What's going on?

A In recent years, many labs have more than doubled their investment in laboratory production equipment. Sometimes it is to provide faster service (anti-reflective coatings or remote ordering, for example), sometimes to produce more accurate lenses or provide better optics or enhanced lens designs such as customized progressives. In every case, faster turnaround service is an overriding concern.

Despite the improved technology, however, there is no way even the largest lab can inventory everything currently available. To do so would mean carrying blanks for every form of lens (single vision, bifocal, and progressive) in each index, in addition to products like all the photochromic versions available in mid- and high-index materials.

Consider progressives. There are at least 150 variables in progressive lenses (older progressives are seldom discontinued). Labs have developed overnight delivery arrangements with lens suppliers for older lenses they don't inventory, but it still adds a day or two to turnaround time. It's an annoying problem, but it's is also why eyecare providers can provide an astounding variety of lenses to their patients.

HIGH POWER PHOTOCHROMICS

Q  Is there an upper limit to the foci range for photochromic plastic lenses? Do photo-chromic lenses work properly when the prescription is a strong plus or minus?

A When all lenses were glass, strong corrections did not work well in sun tints. Strong plus lenses would end up so dark in the center, they were almost black. The centers of strong minus lenses would be so thin, they offered little sun protection.

Today's modern photochromic plastic lenses have, however, overcome this limitation. The darkening process takes place on or near the lens surface, so even a strong plus or minus lens will have an even density across the lens in the darkened state, regardless of center thickness. As a result, virtually any prescription should work well in photo-chromic plastic.

There is one foci limitation of which to be aware. Extremely strong plus or minus corrections require very steep or very flat front base curves, which are not always available in photo-chromic plastic. Your laboratory can advise if the strong powered lens you want is not available.

Computer Vision Syndrome--Real or Imaginary?

Q How can I learn more about computer vision syndrome (CVS)? One colleague tells me it is an "imaginary" complaint, but I believe my patients when they complain about eye strain when working or playing on a computer.

A CVS is a relatively new visual complaint that wasn't recognized until computers became a major lifestyle activity for spectacle wearers. This increasingly common complaint comes from the differences in how written data is viewed on computer monitors compared to printed sources (pixels of light vs. ink and paper). There is far too much scientific data accumulated on this subject to consider CVS as anything but a very genuine visual complaint. Go online to your favorite search engine and ask the question, "What is Computer Vision Syndrome?" You will find a wealth of information on this complex subject provided by a broad array of suppliers and professional organizations.

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.