This is a reprint of a 2020 CE, part one of three with kind permission of the 2020 CE Study Center.
For most of the last century, eyeglasses were fabricated using a binocular measurement for pupillary distance, and simply dividing it in half to center the lenses for each eye. This method delivered apparently great patient satisfaction, as visual complaints were not clearly traceable to the lack of using a "proper" monocular PD....even for segmented multifocals. But exactly what does "not hearing complaints" tell us about how well we satisfy our clients, or more importantly, meeting their expectations? Do we really know whether "not hearing complaints," i.e. good enough, is in fact, good enough?
The answer is that we don't, because not hearing complaints is an imprecise metric of customer satisfaction. Ultimately, the best we can say is that an absence of complaints means that our clients are being served "adequately." But in the online-connected world of today, where consumers are finding information access quick and easy, many are becoming close to experts in their knowledge of the latest in product information about lenses, frames and measuring technologies. For an eyecare professional, this means that their customer satisfaction goals have to be ratcheted up to higher levels than ever before.
Offices relying on a performance goal centered on adequate are bound to find it woefully inadequate as an effective, long-term business strategy.
Today, practices must now focus exclusively on achieving absolute excellence, always attempting to exceed client expectations in every pair of glasses sold. It may have previously been sufficient to possess a rudimentary knowledge of the latest lens and fitting technologies, but a contemporary eyecare professional needs to go further...much further.
They must readily master and implement the latest skills and technologies into their everyday practice to ensure they are fully delivering on the promise of "wowing" their clients. Optimizing single vision and progressive lenses, using individually tailored measurements for vertex distance, pantoscopic tilt and wrap angle, is therefore absolutely essential in guaranteeing consumers receive all the superlative acuity, comfort and utility possible in today's advanced lenses.
ASSUMING THE POSITION
Although frames and faces may come in a wide variety of styles and sizes, engineers working with traditional single vision and progressive designs had little choice in deciding what distance, tilt and wrap angle values a frame would place the lenses. Therefore they settled on averaged values calculated from vast amounts of real-world fitting data. Examining this data, they found that on average, most lenses would be positioned approximately 13mm in front of the eyes for vertex distance, 10 degrees for Pantoscopic lens tilt and 5 degrees for frame wrap angle, otherwise called position of wear, or POW.
For years, engineers employed these 'default' values in their calculations. But with the arrival of free form processing, manufacturers recognized that significantly higher levels of optimization would be possible if individual position of wear values were included in their calculations. This is not unfamiliar to ECPs who have experience fitting stronger power, post cataract or contact lenses. Having to compensate for the difference in vertex distance between the measured phoropter value and the lens fitting value was a routinely encountered task.
THE EXPANDED OPPORTUNITIES OF FREEFORM PROCESSING
Today, free-form manufacturing enables real-time lens design and optimization of single vision and progressive lenses. Because FF processing enables the use of a variety of molded, semi-finished lens blanks, a tremendous expansion in the number of material, design and treatment options is now available for almost any lens design.
Although FF lenses may be ordered in the traditional way, using PDs, heights and simple frame dimensions, the greatest benefits are only realized when an actual tracing of the frame shape, containing exact dimensions and contour, is uploaded to the lab's lens management system (LMS). You next enter the specific POW values, which were taken during the fitting. With this information, the lens software will automatically optimize the progressive corridor and entire lens surface, according to the design choices made by the lens designer. However, there are more tailored and advanced optimizations possible if ECPs also avoid relying on the default design assumptions created by the original engineers.
For example, even with advanced free-form processed lenses, wearers can often encounter adaptation or utility issues in a single pair, or when switching between multiple pairs of eyewear. This is avoidable if ECPs are more involved in determining the lens's overall design priorities, such as specifying the exact length or slope of the progressive corridor. Eyecare professionals are clearly the ones best situated to engage in advanced lens optimization, as they possess a far more intimate and comprehensive understanding of their patient's needs, wants and eyewear style preferences than a lens designer or lab could ever have.
Included amongst the advanced tailoring and personalization options are choosing a distance, intermediate, or near weighted design. By helping patients specify their order of vision priorities, optimization of vertex distance, pantoscopic tilt and wrap angle, individually and together, improve overall lens design and performance.
From "One Size Can't Fit All, (M. Mattison-Shupnick, 2020mag.com/CE), matching the patient to a weighted design lens provides a further tool to get the lenses right. For example, today's mobile lifestyle changes 'normal' reading position and posture. If one asks, "Tell me about your work, where do you do your most reading, show me how you hold the book (tablet and/or smartphone) and the first two reasons that you wear prescription glasses", it's easy to suggest a Near-priority (N), Far-priority (F) or Balanced (B) progressive lens platform. Use Near for indoor/office environments where there's a need for clear, stable, prolonged near vision. Presbyopes who use their eyewear mainly for distance and outdoor work where a clearer and wider periphery enhances the field of view (truck driver, myopes where reading is less in demand) would notice a difference with distance vision optimized. For new presbyopes and people whose demands vary widely, use a balanced design lens.
Barry Santini graduated from New York Technical College in 1975 with an AAS in Ophthalmic Dispensing. He is a New York State licensed optician with contact lens certification, is ABO certified and was awarded an ABO Master in 1994. As sales manager for Tele Vue Optics from 1987 to 2003, Santini developed his knowledge of precision optics and has been an owner of Long Island Opticians in Seaford N.Y. from 1996 to present. In addition, Santini is an amatuer astronomer and lecturer and plays bass trombone in the Brooklyn Symphony.