Occupational multifocals are seldom used, but when they're needed, they're really needed. It's easy to forget how to work with these lenses if you don't see them very often. Double Ds, double Executives, occupational progressives for "office" distance wear (intermediate and near only), golf glasses... these all fall into the occupational category, and all require their own special handling. We've called on the experts to provide some tips on making these important jobs come out right every time.

Topless Segs
PROBLEM: Most of the top segment of an occupational double bifocal lens gets cut off in the edger.

SOLUTION: The lab should work closely with the optician who takes the measurements to make sure that there is enough room in the frame for the patient to be able to use both segs. The upper segment is at a pre-determined height-14mm apart in the case of a Double D. Once the lens is laid out and blocked, the lab tech should hold the frame or the pattern up against it to make sure that enough upper segment will be left for the patient to look through when it's mounted.--Stuart Watson, National Optronics

Blind for Fashion
PROBLEM: Some patients who choose very fashionable frames for their occupational progressives bring them back complaining that they can't see.

SOLUTION: A lot of high-end, trendy frames are pretty small, some with B measurements of 22mm. The position of the reading area in an occupational progressive is determined by the pupil height measurement. People can spend $200 or $300 for designer frames with a narrow B, and they won't get a full window. It's up to the dispenser to mention that there will be a limited field of near vision when they're fitting the frame, and to advise the patient to choose a frame with a larger area.--Bill Galindo, ODI/Topcon

Off Its Axis
PROBLEM: Double Executives and E-D Trifocals come out off-axis, but other occupational lenses are right on.

If there is too much "step" between the add and the distance portions of the Executive style lenses, many labs "double-tape," or make up the difference by using two leap pads. But that sponginess from the extra pad can cause axis twist in the edger. Instead, block the lenses on geometric center, the place on the lens where the step will be the smallest. In order to block the lens manually, the operator must choose to block the lens in the passive mode if using a patternless edger.--Franco Aluigi, Sr. regional manager, Santinelli International

Hyperopic DEs
PROBLEM: Hyperopic Double Executive wearers have problems with headaches and eye strain, but myopic wearers don't seem to have the same discomfort.

SOLUTION: A Double Executive is a one-piece lens design, which means that it has essentially only a distance optical center, and no near OC. With a plus-on-plus lens (both distance and near Rxs are plus), patients will have more problems with eye strain because of induced prism. The eyes converge when the patient looks through the near portions of the lens, but the optical center is placed farther apart in the lens, for the distance area. A minus distance and a plus add will cancel each other out somewhat to eliminate the prismatic effects, but the higher the add on a plus lens, the more prism is induced. The best solution in this situation is to switch the patient to a wide Double D, which has separate OCs for distance and near.--Tim Dixon, Technical Services Coordinator, WECO International

Golf Goofs
PROBLEM: Patients who play golf often need bifocals in order to see to write down their scores, but the bifocal segment interferes with their golf swing when they lower their heads to hit the ball.

SOLUTION: The proper bifocal placement in occupational golf glasses is out to the side of the lens, either up higher or super low. When the seg is at the normal height, the wearer looks through the bifocal, which messes up depth perception. Measure for proper seg placement by having the patient mimic the position they're in when they swing their clubs.--Tracey Morrison, OWC

High Cyl Woes
PROBLEM: The bevel never comes out properly on high-cylinder Double Executives.

SOLUTION: If there is a lot of cylinder in the lens, there will not be a uniform thickness around the edges, making it hard to bevel properly. The best way to get a good bevel is to jog the machine back and forth, making a gradual progression from the center to the top and the center to the bottom of the lens. It's also important to make sure that the lens doesn't tilt and that it stays square in the edger; otherwise, error can be induced.--Michael Urban, Gerber Coburn

Your Bevel Runeth Over
PROBLEM: The bevel tends to run off the edge of Double Execs.

SOLUTION: Use the bevel-control feature of the edger if it has the ability to work off the back side of the lens. If it runs off the front side of the lens, the machine has to make an adjustment where the lens steps down. With a free-float system, your best bet is to run the lens big and hand-edge the bevel.--Matt Vulich, AIT

Got a question you'd like answered in a future "Eye on Equipment" column? Send it now!