Most of the time, people don’t get excited about eyeglass lenses. But every so often, technology takes a major leap forward that promises to revolutionize the industry.

In recent years, manufacturers have raced to market with new free-form progressive lenses that offer undeniable benefits to wearers and are selling like hotcakes.

On the heels of that overwhelming success, manufacturers are brining digital production to the single-vision lens market.

The digital lens trend

Digital progressives caught on quickly because the advantages are fairly obvious to wearers. Today, more than half of the progressive lenses Essilor sells in Canada are digitally produced, and that may be on the low side of the trend. Digital lenses account for 60–70 percent of progressives at Hoya, according to Tom Scott, the company's professional services manager. According to Paul Faibish, president of Plastic Plus, the Toronto laboratory that is also Canada’s exclusive distributor of Seiko lenses, more than 80 percent of the progressives he sells are now digitally produced.

But premium single-vision lenses are a tougher sell than premium progressives. While progressive lens wearers are used to discussing their lenses with ECPs, the single-vision market is dominated by stock lenses that can be edged and passed on to the wearer very quickly, often with little or no discussion about options. And in this age of big-box and discount stores, consumers are demanding ever tighter margins.

Why go digital?

If you ask Tibor Martz at Nikon, it’s because they’re better lenses and patients deserve the best visual correction they can get. His company recently introduced the SeeMax digital single-vision lens and its more customized cousin, the SeeStyle.

“With single-vision lenses what happens, be they spheric or aspheric, the field of vision up front is bigger, but they’re restricted to in and around the optical centre. With this lens, we could control the aberrations or distortion. And for people with high cylinder, as the cyl increases, it maintains the quality of vision with less distortion and skewing of the image,” he says.

The company introduced two lenses, in part to make one that is more accessible to a mass market while also having an ultrapremium lens that pushes the limits of what can be done with available technology.

But there are market factors at play here, too. The single-vision market is big, perhaps 4 million pairs of lenses per year in Canada. But it’s been neglected in recent years, as manufacturers duked it out in the premium progressive market, with an endless stream of new designs.

Also, as margins get squeezed toward non-existence at the bottom of the single-vision market, a new premium product provides the only opportunity for growth. And new technology is what will command that premium. In most cases, digital single-vision lenses cost patients $50-100 more than a high-end conventional single-vision lens.

Essilor enters the market

Essilor, the world’s biggest lens company, entered the digital single-vision market in February 2009, with its Essilor 360 SV.

“It’s more an optimization of the lens. With 360, we can get high-resolution vision, which means we can optimize the classical aberrations, but also the high-order aberrations,” says Descamps. “The high-order aberrations are the ones that are linked to contrast perception. If we reduce high-order aberrations, we can give the wearer a contrast that can be up to more than 40 percent compared to a standard single-vision lens.”

Hoya's digital single-vision lens

Hoya came to market with the NuLux EP, a double-aspheric lens with a free-form, atoric back surface and an aspheric front surface. In that, it’s similar to Rodenstock’s Impression Mono, a customizable free-form lens that won the 2006 Silmo D’Or award for lenses.

“The benefits are the same as going from a spheric to aspheric front on a conventional lens with a toric or bitoric back surface. The challenge comes in being able to calculate a free-form surface with such an inconsistent front surface. Just with the curves that are changing toward the edges of the lens, it’s much more difficult,” says Scott.

Conventional single-vision lenses were usually designed based on horizontal and vertical eye movements. That, he says, is a mistake, since almost all eye movement involves oblique rotation.

“The consequence is that you get astigmatism in oblique directions, no overlapping axis, refractive errors, prescription correction is not accurate then, off-axis prismatic correction, and deformed image perception with a standard spherical lens. When you move to biaspheric designs, aspheric on the front and atoric on the back, with the calculations, off-axis astigmatism, with proprietary software and design technology… we can control and eliminate much of that stuff. The calculated visual acuity, that means the correction outside the optical centre, for power error astigmatism, can be calculated based on things like eye rotation, unwanted astigmatism and removing that,” he says.

Every maker of digital free-form lenses agrees that the main difference with the new technology is a greater ability to control aberration and distortion, particularly toward the periphery.

The difference between conventional and digitally produced lenses is more noticeable to progressive lens wearers, which is part of the reason why the industry introduced the technology to that market first.

Similarly, in the single-vision market, the benefits will be most noticeable to people with high prescriptions, and particularly with high cylinders.

Nikon an early entrant

As good as many conventional single-vision lenses are, be they spherical or aspheric, they do not control aberration and distortion as well as digital lenses.

“Every patient who needs a lens should benefit from the best lens available. Having said that, we all know there are things like pricing that exist also. But from a design standpoint, the designs are not similar but are aimed at the same end goal: to provide the best possible vision for a single-vision lens wearer,” says Martz.

Nikon began its move into the customizable digital lens market in 2005. Its SeeMax is a double-aspheric lens optimized for an individual frame shape. More recently, it introduced the SeeStyle for high-base lenses, which adds more parameters for individualization for wrap angles, pantoscopic tilt and vertex distance.

When manufacturers began producing digital free-form progressive lenses, they quickly moved to introduce highly customizable products, and the same trend is continuing in the single-vision market.

Zeiss and customized single-vision lenses

Some, such as Carl Zeiss Vision, are already there. The Zeiss Individual lens has fitting heights of 13–35 mm in 0.1 mm increments and can be designed for an individual’s monocular PD, pantoscopic tilt, vertex distance and wrap angle.

Those that don’t have customizable lenses soon will. Essilor, for example, plans to launch new, customizable single-vision lenses later this year.

Seiko the newest digital single-vision player

The newest entry to the digital single-vision market is Seiko. Their new SuperMV 1.67 lens came to market in the autumn of 2009. It marries an aspheric front with a free-form back surface on low base curves to reduce power error, distortion and marginal astigmatism.

As the year progresses, expect to see more new digital single-vision lenses. Also expect a wider offering as more manufacturers add features such as polarization, Transitions and different materials to their availability.

Today, the digital single-vision market is small, perhaps only one percent of single-vision lens sales or as much as 10 percent of the premium single-vision lens market.

However, if the experience in progressive lenses is anything to go by, expect these lenses to explode onto the market very soon. Remember, a year ago less than one-quarter of progressive lenses were free-form. Today they make up closer to two-thirds of the market.