“We can do more with lenses than ever before to improve our patients’ vision,” says optometrist Peter Shaw-McMinn, assistant professor of clinical studies at the Southern California College of Optometry and senior partner of Sun City Vision Center, Calif. “Remember, theoretically, we should have 20/6 to 20/8 vision, which is about three times better than 20/20. New lens technology is getting us closer.”
Today’s new age ophthalmic lenses compensate for effective distance, pantoscopic angle, panaromic angle, higher-order aberrations (HOAs), unwanted astigmatism from progressive addition lenses (PALs), pupil size, head and eye movements, he adds. New-age ophthalmic lenses use digital surfacing, which allows each lens to be customized. “I compare it to a bee’s vision, which comes from hundreds of ‘eyes.’ It allows a lens to be surfaced in an infinite amount of combinations allowing compensation for irregularities that distort vision,” Dr. Shaw-McMinn says.
The common theme in the manufacturing of these lenses is much less potential for human error, says Jason Miller, O.D., M.B.A., of Powell, Ohio. Many of the older designs are cut with a diamond tool and surfaced in a lab. “The ‘new age’ lenses utilize high-tech computer programming and laser-edge surfaces to produce a better product,” Dr. Miller says.
These new age lenses come in three distinct categories, Dr. Miller says:
• Digitally surfaced or free-form technology lenses that can “personalize” the Rx to the patient’s requirements. “These lenses help correct the higher-order aberrations, which occur mostly in the distance,” Dr. Miller says.
• Lenses can be designed to correct the wavefront aberrations of the eye. Wavefront measurements and the data collected are used to create an optical fingerprint of the eye.
• “There are lenses being developed that have ‘electro-active’ focusing systems. They are instantly ‘on’ for intermediate and near,” Dr. Miller says.
In addition to advances in technology, designs of these custom lenses have also expanded in recent years to include single vision, progressives, near use, anti-fatigue lenses, computer lenses and lenses with base-in prism for near.
“The biggest advantages with each of the ‘new age’ lenses are improved optics, improved vision and more ‘patient friendly’ wear,” Dr. Miller says.
New Age Lenses
Here’s a look at some of the latest custom ophthalmic lenses on the market and the specific advantages that manufacturers say they provide:
• iZon Progressive (Ophthonix). This lens uses a wavefront aberrometer to correct HOAs and inherent lens aberrations. The iZon is the only customized PAL driven by a patient’s unique iPrint (the optical fingerprint) to address the vision problems associated with both lower- and higher-order aberrations of the eye, according to the company.
Both the iZon SL Lens and its predecessor, the iZon ML Lens, are produced from the patient’s iPrint (which contains all second- to sixth-order aberrations of the eye measured by the Z-View Aberrometer). The iPrint, coupled with the company’s proprietary algorithm, is used to determine the best sphere-cylinder fit for the back surface of the lens.
• Varilux Physio Enhanced (Essilor). Essilor launched its next generation of Varilux Physio lenses in February. The new Varilux Physio Enhanced lens, designed with W.A.V.E. Technology 2, provides the sharpest vision at every distance, even in the most challenging low light conditions, the company says. Variation in pupil size due to age, patient prescription, light conditions and viewing distance can lead to less sharpness in lower light conditions. W.A.V.E Technology 2 takes into account these four factors and manages distortions in the lens even more efficiently than the current Varilux Physio, so the patient sees improved sharpness in any light, less eye strain and reduced swim. Varilux Physio Enhanced lenses are available at all fitting heights of 14mm to 25mm+. Varilux Physio Enhanced lenses are dual-sided, digitally surfaced lenses and offer wider fields of vision than Varilux Physio lenses.
• Zeiss Individual (Carl Zeiss Vision). This lens compensates for the everyday impact of how lenses are worn, delivering maximum visual acuity centrally and in the periphery, according to the company. The lens technology incorporates measurements of how lenses are actually worn into the design of the progressive lens, including monocular PD, pantoscopic tilt, back vertex distance and frame wrap angle, the company says.
The Zeiss Individual is uniquely designed for each wearer using Carl Zeiss Vision’s proprietary optical design engine and patented free-form technology. Using parameters supplied by the eye care professional, including the wearer’s prescription, fitting geometry, and frame information, this powerful optical design engine performs complex calculations online in a centralized server computer. Each lens design is manipulated in “real time” by this optical design engine using data specific to the wearer in order to create a truly unique and fully customized progressive lens design. The final lens calculations are then transmitted to state-of-the-art free-form surfacing equipment for fabrication using Carl Zeiss Vision’s exclusive Precise-Form technology.
• The Kodak Unique (Signet Armorlite). This lens uses proprietary production technology that automatically customizes the lens design for the patient’s frame selection. This ensures overall visual performance for any B measurement, from a fitting height of 18mm to 13mm, according to the company.
Kodak also has added anti-fatigue progressive technology to its line of customized lenses, which incorporates base-in prism in the reading area of the progressive lens that assists the normal binocular function of a patient’s eyes.
• Hoyalux ID (HOYA). This lens is made with free-form technology. It is an integrated double-surface PAL made with HOYA digital surfacing technology, which separates the performance of the front and back surfaces of the lens. It virtually eliminates swimming and swaying sensations for the wearer, according to the company. These lenses offer balanced and more comfortable peripheral vision; a wide intermediate corridor; more unlimited distortion-free areas; perfect transition between far and near vision; and 14mm minimum fitting height, according to HOYA.
• Shamir Autograph II (Shamir). These digitally surfaced lenses use free-form technology. The Shamir Autograph II is a new variable lens design for minimum fitting heights starting from 11mm and up. The Autograph II-Attitude provides the patient with a premium wrap progressive with optimal zone widths and clear, distortion free viewing. The Autograph II-Office is designed for individuals in their work space and provides patients with intermediate and near vision zones for small environment settings. The Autograph II-Single Vision allows single vision patients the chance to experience customization in a fully aspheric back-surface lens. The Autograph II-Single Vision Attitude provides a customized lens for wraparound frames without distortion.
On the Horizon
Pixel Optics is on the threshold of releasing the first commercially available electronic spectacle lens. This new development in ophthalmic lenses has no dividing lines or an obvious progression of power, despite allowing clear focus from far to near and everything in between.
In addition, the lens will deliver an appreciable reduction in lens distortion typically experienced with bifocal and progressive addition lenses, which is achieved thanks to the variation of the index of refraction of an electro-active layer located within the lens.
While these new age ophthalmic lenses provide great advances for patients, there are still limitations.
“Limitations mainly involve visual field and what higher-order aberrations can be improved,” Dr. Shaw-McMinn says. “For example, if you want a large near field with a presbyopic computer user, you would use a variable focus design instead of a PAL. Correcting the higher order aberrations exactly would result in a ‘sweet spot.’” Algorithms are used to correct it throughout the lens to make it as good as possible, he adds.
Another limitation is cost. “These lenses cost more to manufacture, and result in a higher cost to the patient,” Dr. Miller says.
And what awaits in the next generation of new age lenses? “Better correction of higher order aberrations, which arise from irregularities within the eye’s optical system,” Dr. Shaw-McMinn predicts. Wavefront technology will eventually be used by all the companies, he says. “Rays entering the periphery of the lens will be better focused, like those along the optical axis.”
Adds Dr. Miller: “The future is probably in a lens that can be produced at an affordable price and offer the best patient experience.”