By Deborah Kotob, ABOM



Today’s consumer is information driven. They want to know what constitutes excellent performance in the products they purchase, and they want to see how end users rate the performance. How often do you look at customer reviews before buying a high-ticket item? Just as we gain more confidence in a product through the feedback of the tried and true experience of our fellow consumers, so the manufacturer of free-form design progressive lenses can learn and refine their products to reflect real-world performance based on double-blind wearer trials.


OBJECTIVE AND SUBJECTIVE MEASURES FOR EVALUATING FREE-FORM PROGRESSIVE DESIGNS
It takes optical engineers to develop these sophisticated free-form designs and programmers to create algorithms to compensate and optimize the final lens surface according to the base design and the individual wearer’s Rx and frame fit parameters, etc. So how do we glean an adequate understanding of the design differences and benefits to feel confident when offering particular lens designs? The number one factor is identifying pain points for your progressive lens customers related to adaptation, comfort and acuity, such as “swim” and “sway” sensation or narrow fields of view. Next, determine if the lenses solve these pain points.

We use specific and objective data such as the percentage increase in corridor width or area by progressive zone, or a percent reduction in oblique astigmatism or a quantifiable increase in binocular vision to assess the benefits of progressive lens designs. However, as helpful and welcome as objective, measurable, quantifiable data is the proof, as they say, is “in the eye of the beholder,” and this goes beyond theory directly to the patient’s visual experience when wearing the lens. When progressive lens manufacturers provide us with subjective feedback from wearers that report a great visual experience—that they see better and are more comfortable, and when they can even measure the increase in the undistorted field of view, then we can recommend a lens with confidence.

CAMBER STEADY METHODOLOGY
The makers of the Camber Steady progressive lens design (Younger Optics and IOT) provide a combination of both measurable lens performance objective data and subjective feedback from double-blind wearer trials so that we can evaluate and dispense the design with confidence. Their Camber Steady design provides a solution for two of the primary pain-points for progressive lens wearers: 1. The virtual elimination of swim effect, the sensation of motion when wearing a progressive lens, and 2. Increased useable area of the lens for wider undistorted fields of view. Objectively, IOT power maps provide us with the evidence that Steady Methodology virtually eliminates unwanted positive mean power that causes lateral defocus. Subjectively IOT conducted a double-blind study of 45 presbyopes comparing two lens designs. The Camber Steady progressive lens design exhibits a 14 percent increase in distance vision field of view according to IOT wearer trial feedback. “First Impressions” were measured, and IOT reports “a statistically significant improvement of the general impressions when the lens was optimized using the Steady Method. And most importantly, patients perceived the improvements from the first moment they use the glasses, experiencing an amazing ‘wow’ effect.”

How do they do it? Through a unique patented lens design architecture and proprietary surface calculation technology that reduces to null the previously ignored lateral defocus caused by mean positive sphere power error in progressive lenses. The Camber Steady design controls this unwanted spherical power, reducing it to its geometric limits. Before Steady Methodology, lens designers attempted to control cylinder error in the lens but ignored mean spherical power. In the Camber Steady design, the level of unwanted cylinder power is minimized and with smoother distribution. When this design feature is combined with the design’s virtual elimination of positive mean sphere power, the result is a reduction in the swim effect for optimum image stability even in dynamic conditions where the wearer is in motion. This patented lens technology is a breakthrough in free-form lens design that delivers measurable improvements by both objective measures and subjective measures based on the wearer experience. Read the Camber Steady white paper at iotamerica.com/camber-steady-white-paper.

Theoretically, a lens design can be ray traced, the optical performance simulated for all gaze directions, the theoretical best lens surface optics can be digitally mapped out, and the design application tested for precision and repeatability, but it is the experience of the end user that is the ultimate test of lens design performance. To learn more, take the “Merging Complex Curves” CE at 2020mag.com/ce.