We’re on the cusp of a revolution in spectacle lenses—one that’s being driven by digital design and processing. Sophisticated software now allows manufactures to design lenses that account for how vision changes according to myriad factors, such as object position and distance, frame tilt and face form, lens prescription, index of refraction, thickness, vertex distance, pupil distance and pupil size.

The complex curves needed to make these designs work, however, wouldn’t be possible without the introduction of free-form processing, which allows lathing on both the front and back surfaces of lenses, achieving a precision that traditional surfacing cannot approach.

Because of these advancements, today’s lenses offer a level of clarity, visual comfort and personalization (e.g., occupation, hobby and lifestyle lenses) that could only be dreamed about just a few years ago.

In no significant order, here’s a look at some of today’s high-tech lenses and the technology that’s making it all happen.  

Single Vision Lenses
• Advanced Lens Technologies Thin-Tech. Glazing wrapped sunglass frames has long challenged manufacturers; the highly curved lenses needed for them can be bulky and laden with distortion. Advanced Lens Technologies has developed the design and processing capabilities to produce high base curve lenses that are thinner, lighter, have less peripheral distortion, and provide a wider field of view than similar products attempted in the past.

The lenses are adjusted for wrap angle, frame tilt and vertex distance. They also eliminate some of the physical problems associated with mounting lenses in wrapped frames: poor cut out, inability to close temples flat because of thick minus lenses, and eyelashes wiping against the back surface of high plus lenses.

The company can make multifocal lenses with this technology as well.

• Hoya Nulux EP. Employing a design philosophy called Calculated Visual Acuity, Hoya has developed a way to correlate eye movement, acuity and optical aberrations into this lens for a clearer and wider field of view. This bi-aspheric lens is free-form processed on both the front and back surfaces (it’s atoric on the back if the prescription is cylindrical) to optimize visual performance. It’s only available in 1.70 index material.

• Ophthonix’s iZon ML and SL. There are two types of ocular aberrations: low-order (a patient’s prescription), and higher-order aberrations (coma, spherical, trefoil, etc). Only the low-order set could be fully corrected until recently, although it’s the higher-order ones that are responsible for the “lack of crispness” in vision that patients complain about even when they’re corrected to 20/20 or better. These aberrations subtly reduce acuity and contrast, while causing glare and halos.

The introduction of clinical aberrometers is changing this. These instruments measure how light is distorted by the ocular media, and this information is used to design lenses that are superior in performance to traditional corrected curve and even aspheric lenses. Ophthonix’s iZon ML and SL lenses are currently the only ones to employ this technology.
The process starts with an analysis of 11,300 points on each of a patient’s eyes with the company’s Z-View Aberrometer. It creates a wavefront distortion map: an iPrint. The data is then transmitted to Ophthonix, where the lenses are made. The ML lens consists of a proprietary photo-reactive material, known as iZonik, sandwiched between two 1.60-index plastic covers. The front is plano, while the back has the prescription applied to it using free-form processing. The iPrint is programmed into the polymer on a point-by-point basis (The company likens this process to burning a CD). The lens then cures and hardens.

Ophthonix claims patients get “high definition” vision with these lenses due to improvements in best-corrected acuity, low contrast acuity and contrast sensitivity. The ML is available as a PAL as well, and there are sun options (brown, gray and green).

Ophthonix also offers a single layer lens alternative, the iZon SL, which doesn’t perform as well as the ML, but is less expensive. And, it’s also available in Transitions VI Brown and Gray, and polarized brown and gray 3. It too is available as a PAL.

• Seiko Super 1.67 MaxVue. This double-sided aspheric lens has a molded aspheric front surface that incorporates a large 10mm spherical fitting button, which allows generous decentration. Free-form processing on the back surface allows for precise aspheric or atoric curves to minimize power error and peripheral distortion, and to increase viewing area, especially in higher cylinder powers. As its name implies, the lens is only available in 1.67-index material.

• Wiley X DuraLogic. Developed for the company’s eight-base wrapped sunglass frames, these back surface free-form processed lenses compensate for frame wrap, pantoscopic tilt and vertex distance to provide a clearer and wider peripheral view. Like the company’s plano lenses, its prescription lenses also meet ANSI Z87.1-2003 occupational safety standards.

Multifocals
• Varilux Physio Enhanced. The newest member of Essilor’s Physio line is designed with an updated version of the company’s Wavefront Advanced Vision Enhancement technology, W.A.V.E Technology 2. The process accounts for variations in pupil size due to age, lighting conditions, prescription and viewing distance, so the lens provides optimal vision at all light levels with less higher-order aberrations, says the company.

Eschewing regular and short-corridor versions, Physio Enhanced can have fitting heights from 14mm to more than 25mm because the design is optimized for every height. The lens employs the company’s proprietary Dual Digital Surfacing, in which the front surface is created using free-form processed molds, while the back surface is custom free-form processed according to the patient’s prescription.

Physio Enhanced became available in February 2010 in 1.50, Airwear, Trivex, and Thin&Lite 1.60, 1.67, and 1.74, both clear and in Transitions VI Brown and Gray and Transitions XTRActive.

• New Varilux Comfort. This time-honored lens, from Essilor, has been updated to account for the way in which the increased usage of digital devices has changed our visual behavior. Today’s visual environment is more dynamic than in the past and requires constant changes in viewing distance. So, this new lens has wider distance and near zones, less astigmatism in the intermediate zone, and an 8% shorter progressive corridor (85% of the add power is reached just 11.4mm from the distance portion of the lens).
Three products are now available—New Varilux Comfort, New Varilux Comfort Short, and New Varilux Comfort Enhanced, which is free-form processed on both its front and back surfaces for even wider fields of view. In July 2010, the lenses were released in 1.50 and Airwear, both clear and in Transitions VI Brown and Gray, while Thin&Lite 1.60 and 1.67, both clear and in Transitions VI Brown and Gray, were added in September 2010.

• Hoya Summit ecp and cd iQ. These updated versions of the Summit ecp and cd incorporate the company’s iQ technology to apply aspheric or atoric curves to the back surfaces using free-form processing. This enhances acuity at all distances, reduces peripheral distortion, and provides a smoother transition between visual zones.

• PixelOptics atLast!. This composite lens bonds together Trivex on the front and 1.59 or 1.67 on the back. It combines the best features of the materials into a highly impact resistant, lightweight, thin lens. The anterior lens has an aspheric surface, while the posterior lens has a 28mm wide, round segment embedded on its surface.

Because of its location, the segment is nearly invisible and has no protruding ledge. The upper portion of the segment contains progressive optics so that the lens has four zones of vision—distance, far intermediate, intermediate and near. The progressive optics substantially reduce the image jump found in comparable segmented multifocals.

The lens is targeted at patients who’ve had difficulty adapting to PALs, to segmented bifocal wearers who require intermediate viewing, and to segmented trifocal wearers who find the multiple lines objectionable. It’s available in Transitions Brown and Gray.

• Rodenstock Multigressiv Ergo. Available exclusively from ProFit Optix, these near variable focus lenses are available in three designs. “Book” is for use up to 90cm, making it ideal for reading. “PC” is for use up to 120cm, making it perfect for viewing a computer keyboard and monitor. “Room” is for use up to 4m, allowing a greater distance view than the other two. Vision is optimized through the use of free-form processing, and the lenses are available in 1.60.

• Seiko Surmount. Convex Add-Power Curve Technology, an advancement in the company’s internal free-form design, allows the processing of convex curves on the concave surface of the lens. Because lower power base curves can then be used, the lens is flatter and thinner. When combined with new prism thinning calculations, Seiko claims that plus prescriptions can be as much as 25% thinner than competitor’s similar free-form designs.

Unlike the fixed inset used by most PALs, Surmount features Optimized Automatic Variable Inset, a method of precisely calculating the position of the intermediate and near zones based on a patient’s distance prescription and PD for enhanced binocularity. As an as-worn design, such factors as vertex distance and pantoscopic tilt are also accounted for, so the final lens power will be different than what the clinician prescribed.

The lens comes in three progressive corridor lengths––10mm, 12mm and 14mm––so it can be customized to the depth of a patient’s frame and fitting center height. It’s available in Trivex; 1.60, 1.67, and 1.74; Transitions Brown and Gray in Trivex, 1.60, and 1.67; Transitions XTRActive in Trivex and 1.67; and polarized brown and gray in 1.67.

• Shamir Spectrum. This lens is positioned between the company’s Autograph II and Element PALs. It uses the proprietary EyePoint and Direct Lens Technologies, along with free-form processing to provide more stable distance vision and a 20% wider progressive corridor than the Element. It’s available in three fitting heights: 14mm, 16mm and 18mm.
• Signet-Armorlite Kodak Lenses with Anti-Fatigue Progressive Technology. These lenses are designed for patients who experience visual fatigue due to prolonged near work. They incorporate base-in prism to reduce convergence effort for greater comfort. The prism is added to the near zone on the back surface of the lenses using free-form processing. It’s available in the Kodak Concise, Kodak Precise and Precise Short, and Kodak Unique.

Photochromic and Polarized
• Corning SunSensors HPC.
Corning’s original SunSensors and SunSensors+ use in-mass technology, while the new SunSensors HPC (High Performance Coating) has a photochromic compound coating instead. It’s available in polycarbonate, 1.60 and 1.67 in brown and gray.

• Vision Ease LifeRx. These lenses utilize a photochromic-impregnated film encapsulated within the lens (just 0.4mm behind the front surface) when the polymer is injected into the mold. It’s available in spherical and aspheric single vision lenses, FT 28 and FT 35 bifocals (the newest product), a FT 7 X 28 trifocal, and the Illumina and Outlook PALs.

• Transitions XTRActive. Transitions Optical has resurrected this name for a lens that’s darker both indoors and outdoors than their primary product, Transitions VI. Because its photochromic molecules respond to shorter UV wavelengths and visible light in the lower end of the spectrum, it moderately darkens behind automobile windshields. It’s gray when unactivated, and gray-green when activated (to help differentiate it from Transitions VI Gray).

• Transitions SOLFX. This line of lenses was originally introduced as Activated by Transitions Optical in 2005, and the name was changed in 2009. They’re designed to enhance outdoor visual performance by optimizing color and darkness to specific situations, such as driving and competitive/recreational sports. Like all Transitions Optical products, they’re made in partnership with various lens manufacturers.

• Essilor Definity Fairway Transitions SOLFX. Designed for golfing, this PAL employs Transitions’ photochromic technology to change from amber to brown, and comes standard with Crizal Sun Mirrors with Scotchguard Protector. It’s only available in Airwear.

• Specialty Lens Corporation iRx Xperio Transitions SOLFX. Designed for hiking, boating and skiing, this lens combines Transitions’ photochromic technology with Specialty Lens Corporation’s Xperio polarization technology. Available in two colors, ash/dark gray is ideal for true color recognition, while caramel/dark brown is meant to improve contrast and depth perception. It’s available in single vision 1.50 and the iRx Pro PAL.

• Younger Drivewear Transitions SOLFX. Designed for driving, this lens combines Transitions’ photochromic technology with Younger’s NuPolar polarization technology. The lens has two unique features.

First, it changes color depending upon ambient lighting. It’s green/yellow in low light or overcast weather, copper behind automobile windshields and red/brown in very bright light.
Second, because its photochromic molecules respond to shorter UV wavelengths and visible light in the lower end of the spectrum, the lens darkens moderately behind automobile windshields. It’s available in single vision or FT 28, and the Image PAL comes in 1.50 and polycarbonate.

• Zeiss Serengeti Polar PhD Drivers and Polar PhD CPG. The photochromic compound is imbedded 0.9mm into the front surface, while the polarizing element is positioned just behind it. The Drivers are brown for increased contrast, while the CPG is gray for natural colors in all weather conditions. It’s only available in NXT (Trivex) in single vision and as a PAL.

Materials and Anti-Reflective Coatings
• Vision-Ease Thindex 1.70. Introduced in October 2009, this high-index lens material has an Abbe value of 36, which is higher than that of 1.67 and 1.74 and results in less chromatic aberration. It’s also four times more impact resistant than 1.74. It’s available in single vision and the Novella PAL.

• Essilor Crizal Sapphire with Scotchgard Protector. Introduced in April 2010, this isn’t an update of any of the company’s current products. The key innovation is the Enhanced Light Transmission (ELT) System, a light interference-cancelling layer that reduces reflections by an additional 50% compared to Crizal Avanc√©. It also features a SR (scratch resistance) booster layer for greater durability, and an HSD (high surface density) process for better cleanability.

• Zeiss Teflon Elite. Co-developed with DuPont, this Zeiss lens is an updated version of its Teflon Clear Coat. It now permits only 1% visible reflectance, has enhanced hydrophobic and oleophobic properties, and is more scratch resistant.

Electronic Patient Measurement Devices
No matter how technologically advanced lenses become, their full potential can’t be realized without accurate patient and frame measurements. Unfortunately, measuring PDs, fitting heights, vertex distance, pantoscopic tilt, and face form by hand is fraught with potential errors.

While corneal reflection pupillometers have addressed many of the problems inherent in measuring PDs, we’ve only recently begun to see electronic devices designed to measure the other major fitting parameters. Here are a few:

• AIT Center Automatic Patient Measurement System. This device uses three cameras and infrared LEDs to obtain 3-D patient measurements. It’s capable of measuring all of the major fitting parameters, except for face form. The instrument is motorized to increase patient comfort when capturing information.

• ABS Smart Centration Diamond System. This system uses three triangulated, high-resolution cameras to obtain patient and frame measurements. It can also take a frame’s A, B, ED and DBL measurements.

In addition, the device is a powerful marketing tool. First, it can photograph patients wearing a frame and display up to four styles simultaneously for comparative purposes.

Second, it can display thickness and weight differences among many popular PALs by entering a patient’s prescription. Third, it’s capable of demonstrating lens enhancements, like simulating how a patient would look with and without anti-reflective lenses.

• Zeiss i.Terminal. This piece of technology uses a single digital camera to capture both front and side views of patients wearing their chosen frames. It’s capable of measuring the major fitting parameters, and it can also demonstrate lens enhancements while patients are wearing their frames.

The Future
• Behold! This composite aspheric single vision lens, from PixelOptics, bonds together Trivex on the front and 1.67 on the back. The company says it will be the first lens that can be surfaced to less than 1mm at the center for minus powers and have the thinnest centers of any plus power lens of equal power and diameter. It’s also supposed to be up to 20% lighter than 1.74 lenses of equal power and diameter. It’s scheduled to be released in the latter part of 2010.

• emPower! Pixel’s electronic multifocal lens system is intended to allow the wearer to see clearly at any distance without moving parts and without much of the distortion typically inherent in PALs. This is accomplished by changing the index of refraction of an electroactive layer found within the lens.

PixelOptics will partner with Aspex Eyewear, Shamir, Transitions Optical and Panasonic Shikoku Electronics to launch emPower! in late 2010 or early 2011. Aspex Eyewear has the exclusive rights to manufacture the frames required to power the lenses (they’ll have a hidden rechargeable battery). The frames are intended to look just like a current fashion frame, and will be available in metal, plastic and rimless styles. Shamir Optical’s Prescriptor software, which interprets a patient’s refractive, ocular and frame information to direct the free-form processing of lenses, has been selected to manufacture emPower! lenses.

The lenses will have both automatic and manual modes of operation. PixelOptics is collaborating with Transitions Optical for a photochromic version of the lens.

• TruFocals. This spectacle system is the brainchild of Stephen Kurtin, Ph.D., a physicist who has developed electronic and optics products for the past 30 years. It’s composed of two lenses—an inner, flexible lens and an outer rigid lens—with a pocket of fluid between them. When a sliding device mounted on the bridge is moved, it pushes the fluid against the flexible lens, which alters its shape, thus changing the correction.

Only one style of frame is used, although it’s available in several colors. It’s round by necessity, made of a stainless steel alloy, and the bridge size is custom manufactured depending upon PD.

• Adaptive Eyecare. This spectacle system is the creation of physicist Joshua Silver, Ph.D., who wanted to provide low-cost spectacles to people in developing nations. Adaptive Eyecare spectacles have flexible lenses that are filled with liquid by the wearer at the time of dispensing. Wearers can add or remove fluid via syringes temporarily attached to the frame’s temples until they see clearly. Once the syringes are removed and the lenses are sealed, the patient is ready to go.

Each pair currently sells for about $20, although Dr. Silver, now director of the non-profit Centre for Vision in the Developing World, hopes the price can be reduced to about $5.

Dr. Patrick is an assistant professor of optometry at Nova Southeastern University College of Optometry, Ft. Lauderdale, Fla. He has no financial interests in any of the products mentioned.