just how important are premium lens products......to your vendor partners?
By Laurie Pierce, LDO, ABOM
Just how important are premium lens products......to your vendor partners?
...to your practice?
There is no doubt that progress in spectacle lens technologies improves overall patient satisfaction. Exciting new technologies in aspheric lens designs, progressive addition lenses (PALs), photochromics, polarization, and high-index lens materials have made the jobs of eye-care professionals (ECPs) challenging and exciting.
The tough part for us is keeping up with all the breakthroughs. Let's look at the many available lens choices and see why you should-or shouldn't-recommend them to your patients.
Aspherics and PALs
Originally, aspherical designs were primarily used for lenticular aspheric (cataract) lenses for aphakic patients who did not have intraocular implants or contact lenses. Because aphakic patients' lenses were such strong plus powers, crucial light rays would converge excessively through the lens, missing the pupil entirely. That was the impetus for designing a lens that converged light differently from diverse areas of the lens, from outside to center.
Today, aspheric lenses are useful for all types of prescriptions, plus and minus. They enable ECPs to offer a thinner lens with a flatter profile while maintaining superior optical performance.
Aspheric technology is advancing even more in the designs of PALs, from single, to double, and now triple asphericity on a single surface. This added asphericity allows the designer to maximize the curves and prescription in three main meridians: sphere, cylinder, and spherical equivalent. The more meridians that can be maximized for superior optics, the better the vision will be for the patient.
PALs have come a long way as well. PAL designs use aspheric curves to gradually change the power from top to bottom to allow the necessary addition of plus power for near vision. The increase in curvature creates the plus power needed for presbyopic patients. The problem, however, is with an increase in the steepness of curvature from the distance to the near portion, resulting in unwanted excessive cylinder (also called spherical aberration or marginal astigmatism) in the outside areas of the lens. While the visual benefits are clear-more natural vision, elimination of "image jump" found in conventional bifocals-lens designers face the ongoing challenge of keeping the peripheral portion free of distortion.
Leading-edge, premium PALs have much less peripheral distortion and can be customized to specific fitting requirements for each patient. One surfacing technology (FreeForm, Shamir Insight LLC) combines the best of all worlds. Avoiding ceramic molds, this technology creates digital molds, replicating a lens design with accuracy up to 0.01 D. This technology can finish the front of a lens or carve out the entire prescription and PAL design on the back, providing the patient with optimal vision by bringing the optics to the back surface. The process is comparable to the keyhole effect-bringing the optics closer to the eye yields a larger field of view with less peripheral distortion.
The spectrum of lens materials
The earliest photochromic spectacle lenses were made of glass by Corning Ophthalmic Products. They were very popular at the time, because glass was still a commonly used material in optics-there were no options for photochromic plastics. However, the drawbacks-including weight, safety, and varying densities of color (due to lens thickness)-encouraged optical companies to create a plastic photochromic lens. When PPG Industries introduced Transitions lenses (Transitions Optical Inc.), an ocean of opportunities was opened up for ECPs and their patients. Transitions, and other plastic photochromic lenses, have made great strides in percentage of sales in the United States.
Drivewear photochromic lenses (Younger Optics and Transitions Optical) uniquely combine two of the most advanced ophthalmic technologies: photochromics (Transitions) and polarization (NuPolar). Designed specifically to meet the unique visual demands of driving a car, Drivewear is the first polarized photochromic lens to darken behind the windshield of a car, which allows the lenses to change color based on current driving conditions to enhance the driver's vision. In addition, Drivewear lenses are polarized to block blinding glare, another essential attribute when driving.