Wavefront in Eyeglass Lenses

Most of us are familiar with traditional eye exams that measure how well we see. We're shown a series of letters or images on a screen, and then we're asked to select examples with the sharpest focus. Based on what we report to our eye doctor, a prescription for eyeglasses or contact lenses is written.

But what we think we see may fail to genuinely reflect what's wrong with our vision. This is why conventional methods of measuring our vision can be very limited, subjective, and sometimes inaccurate.

With wavefront diagnosis, however, more data about vision errors are detected automatically and almost instantaneously. A popular method of wavefront analysis involves beaming light into the eye, and then "mapping" how light waves travel after they are reflected off the inner back of the eye (retina). If light rays are not bent (refracted) properly by eye structures such as your cornea and crystalline lens, focusing problems can occur.

Wavefront analysis of how the human eye sees now enables eyeglass manufacturers to design lenses that may be better able to correct common refractive errors such as nearsightedness, farsightedness, and astigmatism, along with some more obscure vision errors known as higher-order aberrations.

Wavefront measurements of how the eye sees represent a new technology and until recently have been emphasized primarily with LASIK or laser vision correction. [See also: Wavefront Technology in Eye Exams and Wavefront or Custom LASIK].

In laser eye surgery, a wavefront-guided or optimized procedure involves using a laser to more precisely remove tissue from the eye's surface (cornea) to alter in a highly individualized manner the way light rays enter the eye to achieve focus. These same wavefront principles now are being applied to eyeglass lenses, which also are being designed to more precisely alter the way light rays enter your eye.

These wavefront technology eyeglass lenses are being marketed as a way to achieve crisper vision, beyond what conventional lenses might ordinarily provide.

Wavefront lenses likely will not be fully covered by your insurance plan, if vision benefits are included. Wavefront lenses also cost 25 percent to 30 percent more than comparable conventional lenses, depending on the type of lens you choose.

Beginning in late 2005, eyeglass manufacturers began announcing availability of new lens designs based on wavefront technology as a way to greatly reduce visual distortions and improve lens clarity. Different companies claim unique advantages to their design technologies.

Additionally, many new technology eyeglass lenses in recent years have started incorporating digitalized corrections on both the outside and inside of lenses to achieve better focus. With the extra benefit of wavefront analysis included, these new technology lenses often can achieve much finer precision in vision correction than conventional lenses.

Among the first companies to promote wavefront technology in new lens designs were Ophthonix Corp. with iZon lenses and Essilor of America with Varilux Physio and Varilux Physio 360˚.

Ophthonix creates lenses based on individual wavefront measurements of the eye. Other companies create more generic versions of lenses based on wavefront analysis of visual distortions that can be caused by eyeglass lenses themselves. Because wavefront analysis has introduced a much better understanding of more obscure vision errors known as higher-order aberrations, eyeglass lenses now can be manufactured with much greater precision.

Individualized Wavefront Measurements, iZon (Ophthonix): You can obtain iZon lenses only if your eye care provider has an instrument known as the Ophthonix Z-View aberrometer, which takes wavefront measurements of your eyes to create what the company calls a type of unique optical fingerprint that will be used to custom design your lenses.

All iZon lenses include high index material, along with scratch-resistant and anti-reflective coating. Costs of iZon lenses are about 25 percent higher than comparable conventional lenses.

After an individual wavefront analysis is done, you want to make sure you are a good candidate for these lenses to justify the extra costs. Otherwise, you probably won't notice extra vision improvement with these lenses unless your eye has a significant degree of aberrations that cannot be corrected with conventional lenses.

Beginning in spring 2006, wavefront-guided iZon lenses also were introduced for multifocal or progressive lens corrections of presbyopia. General availability of iZon lenses is limited at this time, but is continually expanding.

Television actor William Shatner of "Star Trek" and "Boston Legal" fame models his new Varilux Physio wavefront lenses at an Essilor event in New York City.

Other New Technology Lens Designs: Wavefront analysis generally has helped provide detailed information about lens-related aberrations or vision errors that previously were not recognized or well understood.

Using this information, companies have developed new lens designs to minimize vision errors previously associated with eyeglass lenses and to help improve the wearer's visual experience. These new lenses also improve lens clarity.

Commercially available wavefront technology lenses, which do not involve analysis of each individual eye, include:

• Varilux Ellipse 360˚ (Essilor of America), in addition to earlier wavefront designs of Varilux Physio and Varilux Physio 360˚.
   
• Zeiss GT2, SOLAOne HD, SOLA Compact Ultra HD, AO Easy HD (Carl Zeiss Vision).
   
• Creation and Autograph (Shamir Insight).
   
• Hoyalux iD and Hoyalux iD Lifestyle (HOYA Lens of America).
   
• SEIKO Succeed and Pentax Perfas (SEIKO/Pentax).
   
• Kodak Unique (Signet/Armorlite).

You will not need an individual wavefront measurement for these lenses. Instead, these lenses are designed in part from your individual prescription created from conventional eye exams. For example, proprietary Essilor wavefront technology known as W.A.V.E. used in Varilux Physio lenses helps eliminate certain vision distortions commonly associated with or not corrected by previously available, conventional progressive lenses.

About aspheric lenses Wavefront-guided LASIK, also called custom LASIK How wavefront technology is used in eye exams What are higher-order aberrations?

Progressive lenses are for older people who have presbyopia, a vision defect that with aging reduces the ability to focus at all distance ranges. Because of wavefront enhancements, Essilor officials say the transition between near, intermediate, and distance zones with Varilux Physio progressive lenses, as an example, is much smoother. In addition, the company claims a 30 percent increase in contrast sensitivity with these lenses, enhancing ability to better distinguish colors and details.

While important for all eyeglass wearers, increased contrast sensitivity is especially significant for people with low vision, such as those who have suffered vision losses from common eye diseases including macular degeneration.

Hoya advertises its new technology progressive lens, the Hoyalux iD, as designed to also adjust for eye movement to prevent visual distortions.

You might consider new technology lenses, particularly if you have difficulty adjusting to conventional progressive lenses for presbyopia. Progressive lenses of this type generally cost about 30 percent more than comparable conventional lenses.
 

In addition to these commercially available wavefront lenses, a company known as PixelOptics Inc. (Roanoke, Va.) is exploring through a Department of Defense grant of $3.5 million development of adaptive lenses that also incorporate wavefront measurements. These SuperVision lenses aimed at surpassing 20/20 vision might some day enhance eyesight of military personnel in the field.

If the technology proves feasible, these lenses would be able to continuously adapt to a changing environment, such as lighter or darker conditions, to alter the way light rays enter the eye to achieve optimal focus. The same company also is exploring potential commercial applications of the technology. [See also: What's New in Eyeglass Lenses]

Ophthonix founder Andres W. Dreher says people who need crisper vision for night vision particularly might be good candidates for his company's iZon lenses, which also provide higher definition vision in the daytime when compared with conventional lenses. He cites studies indicating that wavefront lenses significantly improved night driving responses compared with people wearing conventional lenses. He also mentioned studies demonstrating that certain patients with lingering vision problems following LASIK eye surgery also might benefit from wavefront lenses.

Even people who don't currently wear eyeglasses or contact lenses may be interested in new technology lenses that can correct certain vision defects not addressed by conventional lenses. As an example, a person with 20/20 vision still may have vision distortions caused by vision defects that create problems such as double vision or halos at night.