TECHNOLOGY AND PERFORMANCE MEET FASHION
ZEISS PhotoFusion and DuraVision Flash Mirrors
By Linda Conlin, ABOC, NCLEC
Release Date: September 1, 2019
Expiration Date: September 1, 2020
Upon completion of this program, the participant should be able to:
- Learn about the development and technology behind ZEISS PhotoFusion lenses.
- Learn the benefits to vision that PhotoFusion lenses provide.
- Learn about teaming DuraVision coatings and Flash mirrors with PhotoFusion lenses for fashion and eye protection.
Linda Conlin, ABOC, NCLEC
This course is approved for one (1) hour of CE credit by the American Board of Opticianry (ABO). Technical Level 2 Course STHJHI010-2
THIS COURSE IS SUPPORTED BY AN EDUCATIONAL GRANT FROM ZEISS VISION CARE
Photochromic lenses, aka self-tinting lenses, automatically increase or decrease light transmittance in response to UV radiation exposure. This photoreactive lens category continually improves with technology. Activation and deactivation speed and indoor clarity have all improved dramatically as scientific breakthroughs make the latest iterations better than ever. The impetus for these improvements is consumer demand. Reaction speed and clarity are the lens performance features they value in their light-responsive lenses. ZEISS Photofusion ups the photochromic "cool factor" by offering the lens with fashion tints and flash mirror coatings, making this a convenient high style, fun lens option for those who want style and performance in their eyewear. In this course, you will learn about ZEISS PhotoFusion photochromic lenses and DuraVision Flash Mirror coating to turn the functional photochromic into a standout fashion accessory.
Photochromics have come a long way from their origins when William Armistead made a yellow opal glass lens containing silver halide that darkened in sunlight in the early 1960s. From there, Armistead and research chemist Stanley Donald Stookey filed a patent for photochromic spectacle lenses in 1962. Some of us can recall those early lenses. They were slow to darken and even slower to lighten, never becoming completely clear indoors. They were affected by temperature with reduced darkening in heat and took a long time to lighten after having been exposed to cold. Overall performance declined over time, leaving the lenses with a yellowish cast. Tempering could be done only by chemical methods due to the negative effects on photosensitivity from heat treating the lenses. Because the silver halide was part of the lens material, thinner parts of the lenses were lighter where there was less silver halide, and thicker parts were darker, where there was more. That meant that minus lenses were lighter in the center, and plus lenses were lighter at the edges, making early photochromics a poor choice for higher prescriptions on either end of the lens power spectrum.
Those shortcomings, however, provided the impetus for further research and progress. In 1983, American Optical, which became Carl Zeiss Vision in 2005, developed Photolite, the first plastic photochromic lens. The photochromic properties were the result of a combination of organic photochromic pigments stabilized with a protective inorganic coating. The pigments were imbued into the lens material resulting in an even coloration. The first Photolite lenses were blue when darkened, but because they were plastic, they could be tinted in a variety of colors including gradients to mitigate the blue darkened color, while providing fashionable indoor tints. Unfortunately, these lenses had a lifetime performance expectancy of about two years.
In the more than 35 years since the debut of Photolite, innovation has continued to improve photochromic plastics, resulting in greater thermal stability, that is, less temperature dependence, greater variation between the clear and darkened states and faster reactivity, as well as more color and material choices. The new lenses work using leuco dyes in which molecules can switch between two chemical forms or isomers, one of which is colorless, and the other form darker, depending on the relative balance between thermal and ultraviolet radiation. The darkened state, called activated, occurs upon exposure to UV radiation in sunlight, absorbing visible light. In the absence of UV, as indoors, the molecules return to their colorless or ground state.
PhotoFusion lenses activate with less UV radiation, allowing them to darken more quickly outdoors, about 20 percent faster than previous ZEISS photochromic lenses. Because there is a lower accumulation of UV energy in the darkening phase, the lenses fade to clear up to twice as fast as previous ZEISS photochromics. (Activation and fading times are dependent on temperature, UV exposure and lens material.) How do they work? To produce a ZEISS self-tinting lens, millions of light-sensitive molecules are incorporated into a coating that is bonded to the glass at a thickness of only 0.05 millimeters.
When exposed to UV radiation, the photoreactive molecules temporarily break apart, opening the molecular rings. The molecules then rotate and take on a new form that absorbs visible light (the activated state). When UV exposure is reduced, the molecular bonds resume, the rings close, and the molecules rotate back and return to their original clear (ground) state. (Think of the shade you get when opening a beach umbrella when the sun is up, then the light you see when you close it as the sun goes down.)
That explains the photochromic part, but how can it happen faster? As stated above, the photoreactive molecule rings not only open and close but also change form. The molecules need sufficient space to perform those molecular acrobatics. ZEISS PhotoFusion lenses utilize a larger, more open polymer matrix, or molecular environment, which allows the molecules to change form and reorient more quickly, especially from the activated to the ground state. In a tighter molecular environment, the molecules take longer to change and reorient, which slows the photochromic change, particularly when fading to clear.
Fully activated ZEISS PhotoFusion lenses quickly darken to 11 percent transmission, while the fully clear state is 93 percent transmission, making the lenses fine for night driving. New Extra Grey lenses range from 8 percent transmission when fully activated to 91 percent transmission in the full ground state. All PhotoFusion lenses satisfy the ISO 8980-3 requirements for dark (Category 3) lenses at 73.4 degrees Fahrenheit (23 degrees Celsius).
The energy of electromagnetic radiation increases as the wavelength decreases, and so UV radiation below 380 nanometers (nm) has a higher capacity to disrupt cellular function than visible light between 380 nm and 760 nm. We know that in the short term, bright sunlight and glare can cause ocular discomfort, squinting and eyestrain. Longer exposure times can delay and slow the dark adaptation process, which negatively affects night vision, and excessive glare can impair visual function completely.
Photokeratitis, effectively a sunburn of the cornea, can occur in a relatively short period of intense UV exposure, including reflected sunlight from sand, water, ice and snow. And longterm exposure to UV radiation increases the risk of cataract and macular degeneration. ZEISS PhotoFusion lenses offer excellent protection from this harmful radiation by blocking 100 percent of UVA (315 nm to 380 nm) and UVB radiation (280 nm to 315 nm) up to 400 nm. That goes beyond the current American National Standards Institute/International Organization for Standardization (ANSI/ISO) standard for a material to qualify for "100 percent UV protection," which is attenuation up to only 380 nm. UV protection up to 400 nm fills a critical exposure gap.
The cumulative risk to the eye from indoor blue light exposure is still under review, but studies have shown that chronic exposure to outdoor levels of blue light may increase the risk of age-related macular degeneration (ARMD). Chronic exposure to ultraviolet and short-wavelength visible radiation may have an impact on the function of photoreceptors and the retinal pigment epithelium, causing photochemical damage. As more information is presented, many eyecare practitioners (ECPs) want to offer their patients protection against potential cumulative damage from long-term exposure to both outdoor and indoor levels of blue light, and informed consumers want that protection, too. ZEISS PhotoFusion lenses provide UV protection up to 400 nm, and they achieve up to 22 percent indoor ISO blue light protection and up to 27 percent indoor blue light protection according to the Essilor method. And according to ZEISS, no leading photochromic has more indoor blue light protection than ZEISS PhotoFusion (1.5 material in grey, the most popular color among photochromics, measured at 23 degrees Celsius).
COLOR AND PERFORMANCE
The leuco dyes mentioned previously contain chromophores, which are the chemicals that produce colors by absorbing visible light when exposed to ultraviolet radiation. Each chromophore produces a distinct absorption spectrum when exposed to UV radiation, resulting in a distinct color. Two or more chromophores may be used to achieve a particular color, but different chromophores may respond differently to temperature, resulting in variations from the desired color. The patented chromophores used in ZEISS PhotoFusion lenses have wide absorption spectra that allow for excellent color control. This results in superior color stability with minimal variation in color when activated, and the flexibility to offer more color choices. The visible differences in lens colors are caused by the difference in spectral transmittance for wavelengths longer than 500 nm. High-energy visible light is considered to be the shorter wavelengths below 500 nm. All color choices provide excellent UV and blue light protection.
Like all organic dyes, photochromic leuco dyes are susceptible to degradation by oxygen and free radicals after continual exposure to UV radiation and environmental elements. Over time, photochromic plastics show a reduction in the range between the activated and ground states, the result of photo-oxidation from exposure to UV radiation. What's more, as the chromophores deteriorate, they lose transparency indoors and discolor, a state known as fatigue. Photochromic fatigue can be reduced by adding a UV stabilizer or by providing a barrier to oxygen and other chemicals. This will prolong the expected period of excellent photochromic performance.
ZEISS uses chemical additives in the PhotoFusion polymer matrix that inhibit polymer degradation. These stabilizers act like the antioxidants we take for our bodies to slow down photochemical degradation reactions. This results in less discoloration and loss of transparency in the clear state after prolonged exposure to UV radiation, as compared to previous ZEISS photochromic lenses, thus providing wearers with higher performance and value.
ZEISS PhotoFusion lenses come in five great colors: Grey, the worldwide-preferred color for self-tinting lenses; Brown for enhanced contrast and reduced glare; Extra Grey that is extra dark even in warm climates; Pioneer Green, a classic grey-green when activated; and Blue, an exciting, new fun and fashionable color choice. Every choice benefits the wearer with durability, color consistency, UV protection, outdoor blue light protection and twice the indoor blue light protection as standard clear lenses. PhotoFusion lenses are available in most ZEISS lens styles, progressives, bifocals, trifocals and single vision, as well as polycarbonate and high index materials.
In 1935, Carl Zeiss patented their first antireflective coating (AR). The company today is an industry leader in performance coating technology. Anti-reflective coating reduces the undesired reflected light from the surface of the lenses and eliminates ghost images caused by internal lens reflections that could affect the visual quality required for relaxed, comfortable vision. ZEISS now offers an array of coatings to pair with PhotoFusion lenses. For example, DuraVision Platinum and DuraVision Silver, two ZEISS premium coatings, use an integrated system of coating layers, densely packed using ion-assisted deposition (ion bombardment) to yield a lens surface that is three times harder than the previous generation of hard anti-reflective coated ZEISS lenses. The coating is strong, dirt resistant and easy to clean.
Conventional AR coatings produce maximum residual reflectance near the peak sensitivity of the eye, reducing their effectiveness. The maximum residual reflection of DuraVision premium coatings has been shifted to the blue end of the spectrum for reduced residual reflectance visibility. But it doesn't stop there. While more than 90 percent of UV radiation comes directly from the front, a small part approaches the eye indirectly from the sides and back. As some UV rays may be reflected onto the eye by the back surface of the lens, ZEISS anti-reflective coatings are designed to have low reflectance in the UV spectral range. The back surface UV protection is integrated as a standard feature into all premium ZEISS DuraVision coatings. These coatings deliver what our patients want: Clearer and more comfortable vision thanks to increased light transmittance and greater lens clarity, a better appearance due to reduced reflections and superior hardness for durable, anti-static, easy-to-clean, scratch-resistant lenses.
FUNCTION MEETS FASHION
Patients can now customize their ZEISS PhotoFusion, tinted, polarized or even clear lenses with a new array of mirror and flash mirror coatings. That lets your patients cultivate their very own unique look—and they get the added benefits of on-trend fashion in a high performing functional and convenient photochromic lens. PhotoFusion and sunglass lenses with ZEISS DuraVision Flash Mirror coatings reduce light transmission, and this improves visual comfort, both in extreme light conditions, such as up in the mountains or the snow, as well as on the beach, in the park or when you're shopping or playing sports. While full and flash mirrors are a great add-on for sunglasses that increase the cool factor and the function factor, new flash mirrors are taking photochromic fashion mirrors to a whole new level.
ZEISS DuraVision Flash Mirrors come in four great options: White, Jade, Sapphire and Amber. And in case you haven't heard the chatter, photochromic lenses with a fashion flash mirror are opening up a whole new fashion market for photochromics. Combine this fashion trend with the state-of-the-art photochromic performance of ZEISS PhotoFusion, and it's a win-win for fashion and function.
Cheap sunglasses use cheap flash mirror coatings that scratch and peel off easily, and your patient may have had a bad experience with mirrors in the past. But now you can WOW your patients by offering them the best of both worlds: a cool mirrored lens in fun fashion or sporty colors and the best ZEISS optics. These new flash mirrors have a lower reflectance than standard mirrors. Because backside AR is important to have on mirrors to reduce the reflections from the back of the lens bouncing into the eye, all ZEISS DuraVision Flash Mirrors and standard mirrors come with their flagship backside AR, ZEISS DuraVision Sun. This will improve visual comfort in extreme light conditions outdoors or indoors on a self-tinting lens.
WHAT WEARERS WANT
Photochromic wearers want fast performance—fast to react to UV and darken, fast to return to clear indoors and to return to a truly clear lens without residual color indoors. Photochromic lenses may not be suitable for every situation. For example, automobile windshields block some of the UV needed for photochromics to reach their fully activated state. For driving then, a quality pair of polarized sunglasses may be preferred to reduce the light intensity reaching the eye and to minimize blinding reflected glare, as only polarized lenses can do. Polarized sunglasses are also recommended in environments with intense reflected glare from surfaces such as water or snow. With those exceptions, many eyeglass wearers benefit from the convenience of one pair of eyewear that: 1. Corrects their vision, and 2. Conveniently protects their eyes from harmful solar radiation outdoors. Can you think of anyone who might benefit from the acuity, sun protection and convenience of photochromics? Photochromic lenses are perfect for kids. Kids struggle to keep track of their stuff, so multiple pairs of eyewear and sunglasses are too much for them to handle. They need the correction, and they need protection; in fact, their eyes are more vulnerable to sun damage than an adult eye, and yet only 7.6 percent of parents report that their children wear sunglasses all the time when outdoors. Many of us are outdoors for extended periods without our sunglasses as reported by VisionWatch, which makes photochromic eyewear the perfect choice for our general-purpose pair of eyewear.
When we have photochromic lenses in our glasses, our eyes are never without sun protection outdoors. Eyeglass wearers can be exposed to illumination levels that vary during the day from as high as 100,000 lux (a measure of the intensity as perceived by the human eye of light that hits or passes through a surface) in direct sunlight to less than 10 lux in a dimly lit room—a range of 10,000 to 1! Patients who are light sensitive or who spend a majority of their day going from outdoors to indoors and back again, such as salespeople or real estate agents, will enjoy the convenience of the fast reaction in the ZEISS PhotoFusion photochromic lenses. Be sure that your lens recommendations consider those clues uncovered from targeted lifestyle questions. A pair of glasses that self-tints in response to changes in UV exposure levels provides the convenience many people want, while still enjoying great vision and a fashionable look.
Here is what wearers want in a photochromic lens: quick change from light to dark and back again; lenses that are very dark in bright light, but clear indoors; 100 percent UV protection; attractive tint colors; durability, longevity and high performance. ZEISS PhotoFusion lenses with DuraVision premium coatings check all of those boxes, enabling the ECP to recommend these products with confidence. Be sure to present these features and benefits to your patients when you discuss lens choices.
From poorly performing glass, photochromic lenses have progressed to high performance, fashionable and protective lenses in a variety of lens styles, colors and materials. New technologies have produced lenses that have been engineered with significant improvements over previous photochromic lenses. ZEISS PhotoFusion lenses activate and deactivate more quickly to ambient light levels, indoors and outdoors; offer exceptional protection from harmful solar radiation up to 400 nm and maintain excellent color stability, with minimal loss of photochromic performance over time.
PhotoFusion lenses are durable and can be paired with ZEISS' DuraVision AR coatings and attractive DuraVision Flash Mirrors for added sun protection, acuity and fashion flair. ECPs need to offer patients the best in eye and vision protection to suit their lifestyles with fashion-forward lens choices. ZEISS PhotoFusion lenses and DuraVision coatings provide a great vision solution to fill those needs.