By Brian P. Dunleavy
Optician and educator David Wilson can find a “teachable moment” anywhere. Just ask his aunt.
Watson, a long-time optician and an instructor at the BC College of Optics, welcomed his aunt from out of province just as she was having “some difficulty” with her new progressive lenses. Rather than let her suffer, he decided to use her as an example for his students of what not to do as a professional optician.
“She explained that when she picked up her eyewear, the optician simply gave her the glasses in the case and told her if she had any problems to come back,” Watson recalls. “That was it – no adjustments to the glasses or instructions on how to use them.”
But eyeglasses aren’t that simple anymore, as Watson’s aunt learned the hard way. Today’s lens designs are not “plug-and-play,” to use a term commonly associated with high-tech gadgets, which is exactly what eyeglass lenses have become. With new technology incorporated into designs to help them conform to the unique visual needs of individual wearers, contemporary spectacles lenses offer many new and exciting benefits to wearers – but they can also present new challenges to eyecare professionals in the fitting process.
“Free-form or digital technology in both single-vision and progressives is a wonderful innovation,” notes Steven Levy, owner of LF Optical/LF Warehouse inToronto. “But how effective lenses that use it are for the wearer ultimately comes down to the fit.”
“One of the key messages I tell students is that most progressive non-adapts are usually not patient problems or Rx problems but the dispenser’s problem,” Watson adds. “In other words, a poor or incorrect fit or choice of frame.”
So how can you avoid fitting failures?
Distance relationships
Pupillary distance (PD) remains the most important measurement in lens fitting. Take monocular PDs and use a pupillometer for the most accurate measurement.
Measure up
Ocular centre (OC) and prism reference point (PRP) heights are often overlooked measurements that can make or break a fitting, particularly with free-form progressives, which take multiple measurements into account. “There is much more than just correct PDs in the fitting of progressive lenses and the digitally surfaced lenses of today,” Watson explains.
Take a position
Be sure to measure pantoscopic tilt, fitting height, vertex distance and faceform or frame wrap (the distance the frame “wraps around” the face). Some excellent high-tech devices are available to assist opticians in the collection of these measurements; however, Watson still emphasizes the importance of maintaining a mastery of old-school techniques.
“Know how to take measurements without fancy gadgets,” he says. “Pupillometers and computers break down or are easily put out of calibration. The basics will never let you down. We have a computerized system at the school that takes all the basic measurements. It’s fun to use and the students are always wowed by it. But every good optician I know can measure two or three patients in the same time it takes to use the computer system.”
Make adjustments
Once the patient selects their frame, adjust it before taking any measurements and note its “base curve” (the curve of the eyewire). Again, this is particularly important with free-form progressives. “I was talking to a lab manager at one of the largest labs in Canada and we agreed that this is an industry problem,” notes Watson. “Most non-adapts to progressives come down to the adjustment of the frame.”
Just like Watson’s aunt. How did things turn out for her?
“In class, I helped the students analyze her difficulties and solve the problem. First we inked up the glasses, adjusted them for her head, gave her some more faceform and pantoscopic tilt. She said it was like we replaced her lenses with something better! Her vision also improved two lines on the Snellen chart.”
How fitting.
