FEB 2016

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Your monthly guide to staff training outside the box

Eyes / Lenses / Fitting Lenses / Free-Form / Frames / Sunwear / Patient Solutions / In-office / Standards

LENSES: Fitting and Dispensing


Most eyecare professionals today do not realize that after assessing a client’s visual needs, hobbies and lifestyle choices, they have a responsibility to present to consumers lens materials in a hierarchy of impact resistance. Unfortunately, guided by 35 years of rulings in tort law and product liability cases, this became known as the “duty to warn,” and the recommendation of glass lenses has been subsequently thrown into an undeserved and negative light.

A further deterrent to the choice of glass lenses is the requirement for the buyer to sign an informed consent statement to be kept on file for seven years, detailing the variety and final lens choice selected. This has represented a serious obstacle to doctors and staff prescribing or recommending glass lenses. But in the final analysis, the sale of glass lenses really boils down to whether they are presented in a positive, benefit-filled manner alongside the other material choices. Remember: The sale of plano eyewear and sunwear in non-optical environments is not required to meet the same advisory and record-keeping requirements that businesses who employ doctors or licensed eyecare professionals presently do. Instead of duty to warn, perhaps it’s more accurate to re-characterize the lens advisory process as “duty to advise.”

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Several studies in the last 20 years have attempted to scientifically analyze the accuracy and repeatability of obtaining PDs:

  1. PD Ruler—Measure the distance between pupils, corneal reflections, iris margins and particularly in the case of small children, the inner and outer canthus. A study completed in 2002 assessed that the ruler method could yield values accurate to within 1.54 mm of a gold standard with 68 percent confidence.
  2. Pupillometer—Primarily measures the distance between corneal reflections. Overall values were found to be within 0.74 mm accurate with 95 percent confidence.
  3. Digital Centration Devices (DCD)—These may use either corneal reflections or iris borders for determining PD. The user should be aware if the device’s software employs an internal calculation to extrapolate at the visual axis location from the pupil/iris center. DCDs were found to be very accurate, with binocular PDs within 0.40 mm with 95 percent confidence.

There’s a pattern here: Pupillometers appear more accurate than millimeter rulers, and digital centration devices appear more accurate than pupillometers. But before you ditch your PD ruler, remember that the ruler and manual measurements will always play an important role in an ECP’s toolkit.

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The “wow” factor is twofold for the patient. The first “wow” is seeing how your optical embraces new technology and incorporates it into their vision care. I speak to patients who remember when PDs were measured with rulers, and how revolutionary the pupillometer was when it was introduced. This is simply its evolution and the next tool opticians can add to their arsenal. We already utilize so many new pieces of equipment in our offices such as retinal imaging devices and digital corneal topographers; then why would a simple digital measuring device be overlooked?

The second wow factor is in the final products themselves. Remember the HDTV? Think about pumping that TV full of the highest quality HD programming, and you are suddenly blown away by what you see. So many of my patients have said during the dispense, “Wow! I don’t think I have ever seen this clearly before.” This is your chance to reiterate how all of the custom measurements you took, combined with new digital lens technology, have created an incredible visual experience for the wearer. This is the point to drive home with the patient, and they will remember this experience and rave about it to their friends and family.

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To begin the choice of a corridor length, start with your fitting height and subtract 4 mm to 5 mm, which allocates enough height for a minimum useful reading area. The difference left is a good approximate number to begin determining your target corridor length.

Here’s an example: For a fitting height of 18 mm, corridor length roughly calculates as follows: 18 mm minus 4 mm (minimum reading area height) = a 14-mm Corridor Length Value.

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Here are lenses in cross-section. Look at edge thicknesses (number 5 and 6). One is a lot thinner, lighter and flatter than the other. How much thinner and lighter?

Numbers 1 and 2 show the calculated thinness, numbers 3 and 4 show how much thinner and lighter. Here, virtually half the thickness and 78 percent lighter.

It’s powerful and very professional to be able to immediately show a patient what they get when they pay more. In fact, jot down these kinds of savings for your summary of the sale so the patient leaves knowing a list of all the benefits they purchased.

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Today, as the pendulum of eyewear fashion begins its swing back to smaller eye sizes, iconic shapes and vintage styles, the perfect opportunity to differentiate your practice by specializing in glass lenses is presenting itself. With new thinner, high-impact materials, free-form processing and the application of the latest coatings technology, glass lenses are now offering choices on par with the technology of resin alternatives, but with the renowned optics of glass.

Many independent and OEM labs now exist that can speedily deliver the quality of glass lenses at reasonable prices. Premium sunglass companies such as Vuarnet and Costa are offering the benefits of their branded sun styles in both plano and authentic prescription form. There’s no longer any reason to “weight” before you offer patients the quality of glass lenses.

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Frame wrap angle describes the horizontal angle of the lens plane in front of the eyes. The total frame wrap angle is measured with a common protractor, with one lens placed along the baseline of the protractor, and tracing a line tangent to the nasal and temporal limits of the opposite eyewire. The total wrap angle is then halved to obtain the angle for an individual eye. Unlike Pantoscopic tilt, frame wrap is a non-yoked measurement, meaning the tilt of a lens is opposite for each eye.

Traditional progressive lenses have always benefited from modest wrap angles, in the range of 5 to 7 degrees. Engineers prefer to use these values over a flatter angle because moderate amounts of wrap decrease the obliquity of the gaze angle in the periphery, which also decreases awareness of image degradation or distortion. Again, it is highly important to include the wrap angle when the measured frame value lies outside this range by two or more units in order to ensure optimal peripheral clarity.

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