Whether you are an athlete or just a casual sunglass wearer, high wrap frames are in demand. Big sunglasses with a steep curve that hug the lenses close to the face are the sunglasses of choice for many outdoor enthusiasts, including cycling, volleyball, shooting, running, hiking, sailing, fishing and boating. Even casual sunglass wearers benefit from a large fitting frame including lots of eye and face coverage.
Contact lens wearers, or those lucky enough to not need a prescription lens, have their choice of the pack – from technically advanced frame features to interchangeable lens options – they are not restrained by corrective lens limitations. Sunglasses can be harder to recommend when discussing prescription lenses; the frame wrap sometimes becomes the source of the problem. This begs the question: what options are available for patients who need corrective lenses and desire the functionality of a wrapped sunglass frame?
Curve is the word
The base curve of the lens is the biggest issue with high wrap frames. As you know, the patient’s prescription is formed from a combination of front and back lens curvatures. High wrap frames often require an 8-base lens. The combination of steep curves quickly results in thick lenses from even minor corrections, especially because high-wrap frames typically have large lenses requiring oversized blanks.
Another issue with this rapid change in curvature is the inability to produce a lens with decent peripheral clarity. As the curvature changes away from the ocular center, the prescription isn’t as true and can result in blurriness as the patients’ eyes rotate to use the periphery of the lens. In a plano sunglass, this issue isn’t a problem. The advantage of having a large, curved lens can become a disadvantage with higher prescriptions.
Seeing the solution
With the advent of digital free-form lens technology, the ability to compensate base curvature and surface capabilities to within 0.01 of a diopter, patients can now get prescription lenses in high wrap frames that they may not have been able to get before. Frame manufacturers have capitalized on this technology, and digital free-form lenses are available from manufacturers such as Oakley, Smith, Maui Jim, Costa, Rudy Project, and a variety of others. These proprietary lenses are available in a variety of materials and colors for any occasion or sport and offer a broad range of prescriptions (typically in the range of -6.00 to +4.00 and cyl up to 3.00 diopters in certain cases).
Third party digital free-form lenses are also available through most labs, such as the Sharmir Attitude and others. These lenses can be used in fashion frames with a 6-base lens, or other higher-wrap frames. The advantage of these lenses includes greater clarity as the patients’ eyes rotate away from the optical center, and can dramatically increase their field of vision with higher amounts of astigmatism correction.
Tailor the fit to the patient
Just like tailoring a suit, each prescription is unique to the individual. In order to capitalize on the benefits of new digital free-form lenses, position of wear measurements must be provided to the lab. It is the opticians’ duty to take the additional measurements including pantoscopic tilt, vertex distance and wrap of the frame as worn, along with the optical center for single vision lenses and segment height for progressive lenses). These measurements allow the production lab to properly compensate the prescription lens for the wearer.
A few words about compensated prescriptions: Many opticians I speak with worry about the prescription they receive with the final product. Many times it appears close to the original – but I have seen some “strange” compensation - for example, the first time I saw an astigmatism axis shift over 20 degrees from what was prescribed by the OD. But when the patient tried on the glasses, they mentioned the incredible clarity and sharpness of the lens. Do not be intimidated with what you receive, but I would encourage you to discuss the technology used by your individual lab; a lab representative or technician should give you the education to understand how these prescriptions are generated. And as a bit of a techno-geek myself, I love learning about new lenses as they become available. After all, the result is delivering a better product to your patient.
With summer upon us, patients are gearing up to beat the heat with cool new eyewear. Make sure to ask your patients what they are wearing outside, and educate those who didn’t know about the availability of prescription sunglass options. Hopefully, your optical has stocked up on plano sunwear also, and don’t forget your contact lens wearers – offering a discount off of brand names they might buy at their local Sunglass Hut encourages them to buy with you, and starts a dialogue about the importance of their lens and frame selection. But that’s another article.
Alex Bennett, ABOM. Alex graduated from Colorado State University in 2007 with a degree in Natural Resources Management. He has been an optician since 2008 and currently works in the Denver metro area. Alex is also a contributing blogger for DailyOptician.com and is completing prerequisite courses in order to qualify for optometry school. In his free time, he enjoys running, rock climbing and traveling.