By Deborah Kotob, ABOM

Release Date: May 1, 2022

Expiration Date: May 17, 2023

Learning Objectives:

Upon completion of this program, the participant should be able to:

  1. Describe the key performance factors for photochromic lenses.
  2. Explain the added value of blue violet protection (BVP) built into the clear deactivated PhotoFusion X lenses.
  3. Describe the advancements in ZEISS PhotoFusion X photochromic technology that place it best in class.

Course Description

The photochromic market is changing as is the photochromic consumer. New photochromic technologies feature fun, fashion colors, and flash mirror options attracting a new and younger demographic who enjoy expressing themselves through fashion and love the magic of lenses that respond to light. And advancements in photochromic performance (speed to darken, level of darkness in all temperatures, speed to truly clear indoors) remove the old pain points that deterred past purchases of photochromic. So, the new combination of performance enhancements combined with fun, fashion tints, and coatings are fueling the growth of this eyeglass lens category. But it is also fueling technological breakthroughs such as ZEISS perfecting photochromic performance with the new PhotoFusion X. ZEISS PhotoFusion X lenses are ZEISS’s latest generation and newest photochromic technology. Launched in 2022, PhotoFusion® X improves the rate of speed for activation and fadeback and improves the level of darkness achieved, as compared to previous PhotoFusion photochromic lenses.

Faculty/Editorial Board

Deborah Kotob, ABOM, is the Director of Education and Training for Jobson Medical Information. Her experience spans more than twenty years in the optical industry. During this time, her roles included optical boutiques owner, optician, optical frame sales, and over ten years in lens manufacturing as a Lens Consultant, Trainer, and LMS content developer. She lectures, trains, conducts webinars on a variety of optical, and practice development topics.

Credit Statement:

This course has been approved for 1 Hour, Ophthalmic Level II Course number: STWJHI060-2, continuing education credit by the ABO.


This course is supported by an educational grant from ZEISS.

I always wonder why every pair of general-purpose eyewear isn’t sporting photochromic lenses. Who doesn’t want a lens that magically changes to a sunglass outdoors? Who doesn’t want a lens that’s clear indoors and reduces blue light from screens while providing 100 percent UV and a high level of HEV blue light protection outdoors? This course is about ZEISS PhotoFusion® X, a new generation of photochromic lens technology that overcomes old photochromic objections. In this course, we will learn about how ZEISS is perfecting photochromic performance with ZEISS PhotoFusion X photochromic lenses. This newest generation of ZEISS photochromic technology provides what photochromic wearers want: perfectly clear lenses indoors, fast to clear and fast to sunglass level darkness outdoors. Plus, they provide full UV protection and strong blue light protection. As dispensers of eyewear, we want to have confidence in the lenses we recommend and dispense. To that end, this course is chock full of results from independent and internal studies measuring performance factors of the PhotoFusion X light responsive lenses and consumer studies to determine what is important to the patient when it comes to photochromic lenses.

The photochromic market is changing as is the photochromic consumer. New photochromic technologies feature fun fashion colors and flash mirror options attracting a new and younger demographic who enjoy expressing themselves through fashion and love the magic of lenses that respond to light.

And advancements in photochromic performance (speed to darken, level of darkness in all temperatures, speed to truly clear indoors) remove the old pain points that deterred past purchases of photochromic. So, the new combination of performance enhancements combined with fun fashion tints and coatings are fueling the growth of this eyeglass lens category. But it is also fueling technological breakthroughs such as ZEISS perfecting photochromic performance with the new PhotoFusion X. ZEISS PhotoFusion X lenses are ZEISS’ latest generation and newest photochromic technology. Launched in 2022, PhotoFusion X improves the rate of speed for activation and fade-back and for the grey color, improves the level of darkness achieved, as compared to previous PhotoFusion photochromic lenses.


Consumers often buy a variety of prescription lenses: clear, sunglasses and more recently, blue light protection lenses. But multiple prescription eyeglasses are expensive and cumbersome to manage. Offering a two-in-one solution, photochromic lenses have long doubled as sunglasses and clear eyewear—but never quite perfectly. Early generations were not dark enough or were slow to clear when coming indoors. Slow fade-back speed is a visual inconvenience, as it’s difficult to see indoors with dark lenses, and in social situations they may appear out of place.

Studies from ZEISS and others confirm fast transitioning is important to consumers. In a quantitative survey with N+232 consumers (photochromic lens wearers) in the U.K. in April 2021, 33 percent rated speed to change from dark to light as important, but 57 percent rated it extremely important.

• For many consumers, quick clearing indoors is the most important feature in photochromic lenses.1

• Slow change from dark to light is the most common pain point for photochromic lens wearers.

• “Too slow to go clear” was the most cited technical performance reason for not purchasing photochromic lenses.20

• In the same study, 100 percent of experienced photochromic lens wearers noted “clearing up fast inside” is an important characteristic, even more so than darkness or indoor clarity.

These results indicate a significant gap between the speed of common photochromic lenses and the expectations from both experienced photochromic wearers and potential new customers. Why is fast to clear is so important? We’ve all witnessed someone wearing photochromic lenses that look tinted indoors. We’ve all felt disconcerted when the wearer’s eyes are obscured by lingering tint indoors. This slow speed-to-clear is a common pain point for photochromic lenses and a deterrent for new potential buyers.1 PhotoFusion X overcomes this obstacle to photochromic sales by returning to a clear lens faster than previous PhotoFusion lenses and the most common photochromic brand.21 Consumers will be happy to learn of the faster to clear benefit of PhotoFusion X, and they will appreciate that these lenses provide sunglass level UV protection in all states of activation and deactivation, clear indoors to category level 3 full sunglass tint outdoors. (Category 3 sunglasses: 8 to 18 percent visible light transmission [VLT]) PhotoFusion X lenses now also provide higher levels of built-in blue light protection. This feature is achieved by using ZEISS BlueGuard® lens material as a foundation for the additional PhotoFusion X treatment. Compared to other photochromic brands, PhotoFusion X lenses provide a higher level of blue light blocking—up to 50 percent when inside, and the lens is in its clear state, and up to 95 percent when in a fully activated state outdoors.2 This is important because many consumers are demanding blue light protection around digital screens and artificial light in indoor settings. PhotoFusion X is the newest generation of photochromic lenses from ZEISS, launching in 2022.


Photochromic lenses help consumers manage changing lighting conditions for more comfort and protection. Light is essential for life on our planet and for sight and other physiological functions such as the production of vitamin D in our skin. But excess exposure and cumulative exposure to high-energy light such as UV and short wavelength blue light can present challenges and risks for our eye health and for our visual comfort. Eyeglass wearers have different needs depending on the environmental light conditions experienced throughout their day. When people are indoors, they typically want their lenses to be clear.1 When stepping outdoors, their eyes perceive glare, and they want sunglasses that provide comfortable glare and UV protection. Exposure to the solar spectrum has a positive impact on well-being and mood6, 7 making it vital to spend time outside. During vacation, for example, people spend five to six hours more time outside per day.8 However, illumination levels can vary from 100,000 lux in direct sunlight to less than 10 lux in a dimly lit room. Lighting engineers typically recommend no more than 1,000 lux of uniform illumination for comfortable vision. Compared to direct sunlight, this generates a 100:1 dynamic range. When moving outdoors from a comfortably illuminated indoor environment, eyes must adapt to illumination up to 100 times higher. This sudden increase in illumination is perceived as glare. Glare can be divided into disability glare and discomfort glare. Disability glare is caused by losing luminance contrast from scattered light.9 Discomfort glare is the subjective pain and/or annoyance people experience when exposed to bright light.10, 11 The most obvious trait in discomfort glare is illuminance (i.e., intensity of the light from the glare source at the observer’s eye).12, 13 However, there may be other factors, such as the spectral distribution of the light source. Shorter wavelengths (blue light) generate more discomfort glare.14, 15 Sunlight and digital devices such as computer screens, tablets or mobile phones tend to produce more shortwavelength light.16 Whether glare is caused by changes in light intensity or intense artificial blue light, discomfort glare is omnipresent in our modern world.


Modern artificial light sources and the usage of digital devices are increasing the eyes’ exposure to artificial blue light. While longer wavelength blue light can help us stay alert and awake, shorter wavelengths can generate visual irritation and potentially harm the eyes. High-energy blue (HEV) light is thought to contribute to digital eye strain, causing symptoms like blurry vision and visual discomfort.17 Both the eyecare industry and scientific community have become increasingly concerned about artificial blue light exposure. This has resulted in growing consumer demand for protective eyewear. Consumer interest is driving rapid sales growth in blue light lens sales and eyeglass wearers increasingly searching for “blue light glasses” online. Online search data shows that patients are increasingly interested in blue light glasses. Google searches (Fig. 1) for blue light glasses have increased five-fold in two years.18 In 2020, this term (blue light glasses) outpaced photochromic lens searches.

In addition to scientifically based blue light concerns (discomfort glare and potential harm), this search data indicates how important it is to consumers to provide a solution with a high level of blue light protection both indoors (artificial light sources, digital display) and outdoors (solar light conditions).

Previous generations of photochromic lenses came with limited blue light protection, particularly indoors when lenses are clear. Because photochromic lenses are used all day and in all environments, they should offer a higher level of protection. Wearers want to protect their eyes and vision no matter if they are exposed to artificial blue light indoors or solar radiation while spending time outdoors.

UV radiation is not visible to the human eye but poses potential risks to eye health. Shorter wavelength UV (below 380 nm) does not penetrate deeply, posing only a small chance of causing retinal damage. However, without protection, UV radiation can damage anterior ocular structures and the skin around the eyes. Beyond acute temporary damage such as sunburn, chronic ultraviolet radiation exposure can cause irreversible long-term ocular tissue damage. Because electromagnetic radiation energy increases as the wavelength decreases, UV radiations with wavelengths shorter than 400 nm have a greater capacity to disrupt cellular structures and functions than visible light between 400 and 780 nm. UVC radiation (below 280 nm) is absorbed by the atmosphere. But ocular tissue is exposed to the UVB (280 to 315 nm) and UVA radiation (315 to 400 nm) in sunlight which can damage various structures. UV induced eyelid and periorbital skin damage is common. Experts recommend sunscreen on the eyelids to prevent damage, but people often do not take this safety measure to avoid eye irritation. UV radiation can cause several chronic skin conditions: from eyelid photoaging, skin thickening and subsequent prominent wrinkles, to sebaceous gland damage and skin cancer on the eyelid.

As the eye ages, protective pigments in the lens are converted into pigments that react to UVR, further damaging lens proteins and the lens’ outer layer. When damage accumulates, the lens can develop a cataract, severely compromising vision. Melanoma tumors of the iris are the most common cancer of the eye, and evidence suggests that UVR is one of its leading causes.19 The retinas of young people absorb more of the longer UVR wavelengths which may cause photochemical damage. Because UV poses a significant ocular risk, customers expect their eyewear to provide full protection—especially from photochromic and other lenses targeted for outdoor use. In order to provide high performance, ZEISS has focused on speed, sunglass level glare protection, excellent blue light and UV protection, and high clarity in its newest photochromic lenses.


ZEISS PhotoFusion X is a complete photochromic lens portfolio uniquely designed to satisfy consumers’ needs for speed-to-clear, blue light and UV protection. ZEISS has re-engineered its photochromic system to deliver groundbreaking transition speeds, improved darkness, superior protection and attractive colors—all with the world’s leading optical expertise built into every ZEISS lens. Thanks to ZEISS BlueGuard, which is used as the base lens material, ZEISS PhotoFusion X provides excellent blue light protection in any environment (Fig. 2).


ZEISS describes the new patented photochromic system as the following: “ZEISS PhotoFusion X continues the ZEISS PhotoFusion tradition of delivering market-leading activation and fade-back kinetics, without compromising indoor clarity or sunglass-level activation. PhotoFusion X has a completely new photochromic system, using faster dyes in a robust and more open carrier matrix. ZEISS employs a new generation of specially developed and patented dyes. These ultra-low enthalpy, photokinetic dye compounds (Fig. 3) react incredibly fast, making them clearer indoors, dark outdoors and faster to react than previous generations. Each ZEISS PhotoFusion X lens contains billions of dye compounds, each less than 0.3 nm across, that change shape and orientation based on lighting conditions. The supramolecular polymeric matrix provides a robust framework to deliver toughness and durability, while allowing for intra-matrix space, giving the dyes maximum performance. Energy from UV radiation is absorbed by the photochromic dyes causing the dye compounds to open-up. In this open form, the dyes can absorb visible light which results in a sunglass level tinted lens. The more intense the UV radiation, the darker the lens becomes. Even moderately intense UV will darken them to sunglass level. Without UV exposure, the ambient temperature makes the dyes close rapidly, allowing the lens to revert to perfect clarity.” (Fig. 4)

Measurable results: One of the truly great things about photochromic performance in a lens is it can be measured, and claims can be proven. ZEISS provides both internal and external testing results. PhotoFusion X advancements in photochromic lens technology are born from breakthroughs in lens chemistry. As a preeminent leader in lens manufacturing, ZEISS continues their historical drive to develop technologies and advance optical science to meet consumer demand for better photochromic lenses, clearer, faster (dark to clear and clear to dark and truly clear indoors) even in hot temperatures.

PhotoFusion Brown was upgraded to be over 30 percent darker than the earlier generation brown, and PhotoFusion X Brown maintains this level of improved darkness while delivering improved fade-back speed compared to this upgrade.

ZEISS PhotoFusion X Grey is up to 26 percent darker than the previous PhotoFusion Grey and up to 11 percent darker than a well-known photochromic brand’s latest generation grey.21 (Fig. 5)

All colors in Photofusion X lenses achieve category 3 sunglass level darkness (Fig. 6).


Compared to the previous generation, PhotoFusion X photokinetic dye compounds have equal or improved activation performance when temperatures rise. The clarity/darkness of photochromic dyes are determined by the equilibrium between UV radiation and temperature. UV transforms the dyes into their activated state, while heat deactivates them. In other words, the higher the temperature, the lighter the tint, which is true of all photochromic lenses. In the original generation of PhotoFusion, only the Extra Grey and Pioneer colors were designed with sunglass level darkness at hotter temperatures. In PhotoFusion X, the regular Grey and the regular Brown colors also remain dark at these higher temperatures (Fig. 7). Perhaps most notable is the increase in darkness in PhotoFusion X Grey compared to the previous generation of grey (Fig. 8). At 23 degrees C, it is up to 36 percent darker, and even at 35 degrees C, it is over 29 percent darker.31


Once again, ZEISS PhotoFusion X sets the industry standard for photochromic performance and transition speeds. PhotoFusion X is fast-to-clear and fast-to-dark. Depending on color, material and environmental conditions, PhotoFusion X is faster to clear than the latest generation of today’s most common photochromic brand and even significantly faster than previous PhotoFusion lenses (Fig. 9). The chemistry of photochromic dyes means activation is always faster than deactivation. In other words, time-to-dark is rarely an issue. Time-to-clear is the primary performance gap.

There are many ways to measure photochromic speed, and different manufacturers choose varied metrics to report performance of their latest products. ZEISS sets a high standard when measuring speed-to-clear using a metric that is considered most important to eyeglass wearers. ZEISS’ primary fade-back assessment measures the time it takes a lens to fade-back to a clear level—80 percent transmittance (80%T). Other brands use lower transmittance levels as the threshold, such as 70 percent (70%T), which helps them claim to be fast but isn’t truly clear. 80 percent T matches the ISO 8980-3 definition for a clear lens (category 0). The 10 percent distinction may seem negligible, but it significantly impacts speed results, due to the shape of the fade-back transmittance curve (%T). The curve shows the clearing speed decreases while transmittance increases. For many photochromic lenses, it can take a long time to fade-back from 70%T to 80%T, making the higher threshold the more appropriate measure when judging these lenses.


Zeiss’ photochromic measurements comply with ISO 8980-3 and report fade-back speeds based on the 80%T threshold at 23 degrees C.

PhotoFusion X Pro Grey (Fig. 10) reaches 70 percent transmittance in 2 to 3 minutes of fadeback and is clear (80%T) in 3.5 to 5 minutes (depending on index) which is up to 4.5 times faster to clear than a well-known photochromic brand’s latest generation grey.22 PhotoFusion X Pro Brown (Fig. 11) reaches 70 percent transmittance in 2 minutes of fade-back and is clear (80%T) in 4 minutes (depending on index) which is up to 3.7 times faster to clear than a well-known photochromic brand’s latest generation brown.23

PhotoFusion X Grey is up to 1.5 times faster to clear than the same well-known brand’s latest generation grey, while being 11 percent darker when activated. PhotoFusion X Brown is up to 2 times faster to clear than a well-known brand’s latest generation brown23 while it is up to 10 percent faster than the recent upgrade of PhotoFusion Brown with a similar warm color hue.


Customers often ask for photochromic test results from independent laboratories. To answer these queries, ZEISS collaborated with Colts Laboratories, an independent ophthalmic lens testing company in the U.S., to measure the photochromic properties of PhotoFusion X lenses and compare them to the latest lenses from other brands (Figs. 12 and 13). Colt’s independent test results lead to similar conclusions. PhotoFusion X Pro Grey measures up to 4.5 times faster than a well-known photochromic brand’s latest generation grey, comparing average fade-back speed to an interpolated time to 80%T.


Testing by ZEISS and Colts are both ISO 8980-3compliant. Minor testing procedure differences, allowable under ISO 8980-3, account for small differences.


In addition to increasing indoor blue light protection, speed and darkness, ZEISS PhotoFusion X lenses provide excellent indoor clarity, with up to 95 percent transmittance when combined with DuraVision® AR coatings.25 (Fig. 14) Often, lenses that block blue light show reduced indoor clarity because the added grey/blue color additives impact overall transmittance. However, ZEISS BlueGuard lens materials provide excellent clarity, especially when combined with advanced photochromic dye compounds.


ZEISS PhotoFusion X blocks 30 percent more potentially harmful blue light indoors compared to a well-known photochromic brand’s latest generation. (Fig. 15) This is due to the use of blue light blocking BlueGuard base material.26 ZEISS BlueGuard lens materials block up to 40 percent of potentially harmful blue light. In combination with the PhotoFusion X photochromic coating, the blue light blocking properties of the clear lens rise up to 50 percent in the clear state.26 The sun emits UV and blue light, especially in the highenergy visible light (HEV) range. ZEISS PhotoFusion X provides its highest blue light protection when outdoors and fully activated. When fully activated outdoors, the lens blocks up to 95 percent of blue light.27 Other photochromic brands typically apply their photochromic layer on base materials that often do not block blue light or even UV up to 400 nm. This becomes evident when measuring the blue light blocking properties indoors of PhotoFusion X compared to a wellknown brand’s latest generation.

Many eyeglass wearers want blue light protection indoors when photochromic lenses are not activated, but previous photochromic lenses had less blue light protection. Digital devices are often used indoors. Therefore, blue light protection also should be maximized when lenses are clear. ZEISS researchers found a way to close this protection gap, providing blue light protection in any environment and situation, indoors or outdoors. (Fig. 16) A consumer acceptance survey for BlueGuard lens materials, found wearers feel a comfort advantage when wearing these lenses and using digital devices.23 (Ninety-five percent agree they experience less general visual discomfort, and 95 percent agree they experience less discomfort glare.)


ZEISS PhotoFusion X lenses offer the best level of blue light protection in the ZEISS portfolio in lenses that are not permanently tinted.27 ZEISS quantifies the level of blue light blocking by blueviolet block (BVB), which measures the percentage of the potentially harmful blue-violet light, between 400 and 455 nm, not transmitted by the lens. (Fig. 17)

Shorter blue light wavelengths have higher energy levels, and these photons can interact with biological tissue on a molecular level. The latest ISO blue light report (ISO/ TR20772:2018) notes blue light up to 455 nm delivers the greatest phototoxic risk to retinal pigment epithelium. The report also suggests minimizing blue light exposure up to 455 nm and maximizing longer wavelengths to avoid interfering with circadian rhythm and other important functions. This is precisely how ZEISS PhotoFusion X on BlueGuard lenses are designed.


ZEISS PhotoFusion X lenses provide sunglasslevel UV protection, blocking UV radiation up to 400 nm in both the clear and activated states. (Fig. 18) This protection is built into ZEISS BlueGuard materials. This means PhotoFusion X lenses provide the same UV blocking properties as premium sunglasses.

Premium sunglasses typically offer full UV protection to 400 nm; however, people may not own a pair or wear them on cloudy days. A survey from The Vision Council found only 21.2 percent always wear sunglasses when outdoors.28 Because PhotoFusion X are everyday lenses for use indoors and outdoors, wearers have them on all the time, providing more reliable and consistent protection. As a result, PhotoFusion X lenses can provide the average wearer better protection over time from UV radiation than sunglasses.


The photochromic dyes in PhotoFusion X lenses have been developed with improved hues, closely matching consumer preferences in the sunglass industry. (Fig. 19) Through its sun lens division, ZEISS supplies nonprescription sunglass lenses to many of the leading sunglass brands, giving ZEISS unique insights into sunglass fashions and color choices.


PhotoFusion X Grey has a more neutral greyblack color hue when activated and maintains this tone during activation and fade-back. Compared to previous generation PhotoFusion Grey, these lenses are up to 26 percent darker at 23 degrees C, and even at high temperatures (35 degrees C) are over 29 percent darker. PhotoFusion X Brown has a warm brown tone, with similar darkness but slightly faster than the recently upgraded PhotoFusion Brown. PhotoFusion X Pro Grey and Pro Brown are a breakthrough in speed—developed to be extremely fast to clear. The darkness of the PhotoFusion X Pro Grey is similar to that of the previous generation PhotoFusion Grey. PhotoFusion X Blue received great feedback in the previous generation, so ZEISS retained this color hue and improved photochromic reaction speed. PhotoFusion X Pioneer is also faster and retains the same grey-green hue, which closely matches the popular grey-green sunglass color.


Outdoors, ZEISS PhotoFusion X lenses are performance-optimized photochromic lenses that provide glare, blue light and UV protection. They deliver sunglass-level (category 3) darkness, UV protection to 400 nm and excellent blue light blocking properties. New and improved grey color hues are up to 26 percent darker than previous generation.29

Indoors, PhotoFusion X provides excellent clarity while blocking up to 50 percent of potentially harmful blue light.2 PhotoFusion X provides groundbreaking transition speed. The speed-to-clear is up to 4.5 times faster than a well-known photochromic brand’s latest generation.22 The speed-to-dark is up to 75 percent faster than previous PhotoFusion lenses, achieving over 70 percent absorption in as little as 15 seconds and full sunglass-level (category 3) darkness in 27 seconds.5

In summary: Remember we buy based on emotion, and the WOW factor of lenses that turn our eyeglasses into sunglasses is an emotional response, so be prepared to demonstrate the magic to each and every patient. Wear these magic lenses yourself; there’s no better endorsement. Feel confident recommending the ZEISS PhotoFusion X lenses, and trust them to make your patients happy and photochromic lens wearers for life.

Additional sources provided upon request.

2.Analyses by Technology and Innovation, Carl Zeiss Vision GmbH, Aus 2021. Based on Blue Violet Block (BVB) metric that quantifies the amount of light 400-455nm blocked by the lens, for PFX Grey 1.6 HC only lenses.

5.Testing by independent laboratory in USA in 2021-22 according to requirement in ISO 8980-3. Based on the average speed (%T/min) of activation from clear state to an interpolated time to 30%T at 23C in grey polycarbonate HC only form.

21.Testing by independent testing laboratory in USA in 2021-22 according to requirement in ISO 8980-3. Based on the average speed (%T/min) of fade-back from fully activated state to the interpolated time to 80%T at 23C in 1.50 index HC only form (CR607 version of comparison brand).

22.Testing by independent testing laboratory in USA in 2021-22 according to requirement in ISO 8980-3. Based on the average speed (%T/min) of fade-back from fully activated state to the interpolated time to 80%T at 23C in 1.50 index HC only form (CR607 version of comparison brand).

31.Analyses by Technology and Innovation, Carl Zeiss Vision GmbH, Aus 2021 in accordance to ISO 8980-3. Based on activated state T% at 35C in1.50, 1.60, and Poly HC only form.