Ask The Labs
By Joseph L. Bruneni

THE CHANGING WORLD OF AR AND PHOTOCHROMICS

Q In the early days of photo-chromic lenses, we were advised not to AR coat these lenses. Later we were told to only use certain AR coaters for photochromics, and now their literature says that AR is recommended. AR may be acceptable for photochromic lenses, but I would never recommend AR to patients who want maximum darkness outdoors because AR increases light transmission by some 8 percent. Do you agree?

A I used to believe as you do. Two things changed my mind. At the recent Transitions Academy meeting of 900 lab people from 30 countries, attendees had an opportunity to check lenses with sophisticated test instruments. We tested and determined that a darkened Transitions lens with AR transmitted within one percent of the same amount of light as a darkened lens without AR.

In addition, William Moore, Transitions product development manager, explained that uncoated standard lenses reflect four percent light from the front surface and four percent from the front side of the back surface, leaving 92 percent to reach the eyes.

A darkened Next Generation lens with AR reflects one percent from the front side, but the photochromic molecules reduce light going through the lens in spite of the AR. A darkened lens without AR transmits 15.2 percent into the eyes.

A darkened lens with AR transmits 16.2 percent. It's doubtful patients can tell the difference. AR is a valuable addition to photochromic lenses for two reasons: 1) The lenses are clearer indoors and 2) backside reflections are greatly reduced when the lenses are dark.

THE RIGHT TOOLS MAKE THE DIFFERENCE

Q We have a lot of Asian patients who fall into that "difficult-to-fit" category. Are there any frame lines that cater to this particular challenge?

A The usual problem in dispensing glasses to Asian patients comes from the fact that the bridge of their nose is shallow, sometimes nearly non-existent. The only effective way to hold a frame in position on their face is with adjustable nose pads.

When frame styles were mostly plastic, the only answer was to have the lab install special adjustable nose pads on the frame. This can still be done. Fortunately, many frames today are metal or rimless with adjustable nose pads.

What has become critical for dispensers is skill in adjusting nose pads. This requires two things: Practice and the right tools. The popularity of metal and rimless has inspired tool companies to develop pliers to aid in this task. If you're still adjusting rimless and metal with a basic snipe nose plier, find a catalogue and order new tools. You'll discover what a difference the right tool makes.

Experience vs. Instrumentation

Q I am an experienced optician and prefer taking PD measurements manually with a PD rule. My lab rep (who is not even a licensed optician) tells me I should be taking PDs with a pupilometer. Is this really necessary?

A The introduction of progressive addition lenses led to development of the pupilometer. PALs require precise monocular PD measurements, and these are difficult to obtain manually. An experienced person like yourself may be able to do it, but less experienced opticians find taking monocular measurements by hand difficult and potentially costly. Your lab rep may also be considering the public relations aspect. Patients are more impressed when a high-tech instrument is used to take PD measurements. As skilled as you are, there's always the possibility that patients who have experienced a pupilometer elsewhere might conclude your office isn't up-to-date with modern instrumentation.

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.