Blue Light Lenses with More Protection and Less Reflection

Product Spotlight CE - Sponsored by ZEISS

Brent McCardle, ABOM

Release Date: September 15, 2021

Expiration Date: May 1, 2023

Learning Objectives:

Upon completion of this course you should understand:

  1. Describe the new aesthetic challenge posed by blue filter lens reflections in online meetings
  2. Describe the ZEISS BlueGuard blue hazard calculation and why it differs from the BLH function
  3. Explain what the ZEISS BVD formula measures and why
  4. Explain how short-wavelength blue light exposure affects retinal cells
  5. Explain how long wavelength blue light affects our circadian rhythm

Course Description

This course will review blue light fundamentals, wavelength-dependent effects on retinal cells, circadian rhythm, and how the new ZEISS BlueGuard Lens technology increase protection and reduce reflections.

Faculty/Editorial Board:

Brent McCardleBrent McCardle, ABOC, NCLE
“Brent McCardle is a dedicated educator with 35 years of optical experience. His understanding of the optical industry encompasses all facets including training and development, teaching ophthalmic optics and advanced ophthalmic theory, managing a surfacing, finishing laboratory and dispensary. He learned to become a better teacher and trainer while he was an Instructor at Durham Technical Community College and he continues to train and educate ZEISS ECP’s and ZEISS representatives in his role Technical Education Specialist. Breg.

Credit Statement:

This course is approved for one (1) hour of CE credit the American Board of Opticianry (ABO). One hour, Ophthalmic Level 2, Course STWJHI046-2.


This is a product spotlight CE supported by an educational grant from ZEISS

This course will review blue light fundamentals, wavelength-dependent effects on retinal cells, circadian rhythm and how the new ZEISS Blue Guard Lens technology increase protection and reduce reflections.

As we spend more time in virtual meetings exposed to digital blue light emitted by our screens, the aesthetics of blue-blocking lenses become more relevant. We see ourselves on the screen just as others see us, and we are becoming increasingly conscious of the prominent blue-purple reflections from our lenses with blue light coatings. ZEISS BlueGuard Lenses solve this problem with their in-material blocking function, producing up to 50 percent less visible blue light reflections from digital blue light compared to blue light coatings. The result is blue light protection, total UV blocking, comfortable vision, excellent lens clarity and superb aesthetics.

More than ever before, we’re spending time in front of digital screens. With the enormous increase in online meetings, we all see how reflective our lenses can be, particularly lenses with blue filters. Unfortunately, our digital screens expose us to more blue light emissions creating new challenges for our eyes, while lens reflections create new challenges for lens wear aesthetics. ZEISS BlueGuard Lenses are engineered to balance protection, clarity and aesthetics to mitigate the potential challenges from digital light source exposure and lens surface reflections. Using the latest organic-chemical technology, ZEISS BlueGuard Lenses provides an “in-material” solution that blocks up to 40 percent of potentially harmful blue light while providing complete UV protection up to 400 nm.

While longer wavelength blue light can help us stay alert and promote a normal sleep-wake cycle, shorter wavelengths are irritating, reduce visual acu ity and produce potential harmful effects on the eyes. By design, ZEISS BlueGuard Lenses block a sub stantial portion of the potentially harmful blue light while maximizing the good blue light transmission.


Increased digitalization and modern artificial light sources increase our eyes’ exposure to artificial or digital blue light. The last few years have acceler ated this trend, changing how we work, learn and socialize. Since the pandemic began, worldwide smartphone usage has increased by 70 percent, while laptop usage has increased by 40 percent.1

A peer-reviewed article in the Indian Journal of Ophthalmology showed that 94 percent of partici pants had increased their screen time during lockdowns. On average, screen time increased from 4.8 to 8.6 hours per day.2 Device usage has become an integral part of our daily lives and is likely here to stay, even after the pandemic subsides.


Both the eyecare industry and the scientific community are recognizing increased exposure from artificially-generated blue light. Blue light can have both negative and positive impacts on our eyes—the dualism of blue light. For example, it is scientifically accepted that blue light is essential for our vision, alertness, mood, wellbeing and sleep-wake cycle.

The visible light range for the human eye is between 380 and 780 nm. The blue light band (Fig. 1), between 380 and 500 nm, is an essential part of the spectrum relevant to proper vision performance and crucial physiological processes.

Our vision evolved under sunlight, the most intense natural blue light source (solar blue light). However, LEDs and digital devices have dramatically increased our daily exposure to artificial and digital blue light.


Blue light can be potentially harmful to our eyes. High-energy visible (HEV) light can cause retinal damage. Shorter wavelengths within the blue light spectrum have higher energy and more significant potential to damage eye tissue.

The blue light band between 380 and 500 nm consist of two sub-bands:

1. HEV or blueviolet light, 380 to 450 nm, and
2. Blue-turquoise light, 450 to 500 nm.

Photo-induced eye health risks and the complications of long-term retinal damage like agerelated macular degeneration (AMD) are linked to High Energy Visible light (HEV) exposure. HEV in the spectral range of blueviolet light is an identified causal factor in the development of AMD.3 These high-energy photons interact with biological tissue on a molecular level. There is a general relation between the absorption of higher photon energy and increased potential for detrimental effects on eye health.

HEV has the potential to cause oxidative damage to light-absorbing ocular structures of the retina. Unlike UV radiation, blue light transmits to the retina and is absorbed by the macular pigment epithelium and photoreceptors. One study found blue light can be more damaging to the retina than other spectral colors.4 Scientists have established the blue light hazard (BLH) function, highlighting blue light risks at each wavelength in the range between 390 and 500 nm. BLH is derived from in vitro and animal studies, and describes the weighting function for calculated risk of damage at a given wavelength along the blue light spectrum. The data is also included in various industry norms, standards and publications.

It is appropriate to weigh the potential risks to retinal tissue associated with bright light sources, such as the sun or arc welders. However, according to the CIE International Commission on Illumination5, BLH does not govern common artificial light sources, such as LEDs or digital devices. As a result, BLH is not particularly relevant to blue light lenses. In addition, the latest ISO blue light report (ISO/ TR20772:2018) notes that blue light up to 455 nm delivers the most significant phototoxic risk to the retinal pigment epithelium. Therefore, the report suggests minimizing blue light up to 455 nm and maximizing longer wavelengths to avoid interfering with the circadian rhythm and other functions. As a result, ZEISS BlueGuard Lenses were designed to partially block blue light between 400 and 455 nm but allow transmission of longer wavelengths.

At present, there is no scientifically established action spectrum to specifically weigh the ocular risk from digital or artificial blue light. As a result, ZEISS does not use any action spectrum calculations to quantify blue light blocking.


Blue-violet block (BVB) measures the true percentage of potentially harmful blue-violet light, between 400 and 455 nm, being blocked to minimize HEV blue light exposure and still allow beneficial blue light transmission. Some alternative formulas incorporate a solar spectral weighting factor. But spectral weighting is not an appropriate approach for blue filter lenses because they are designed and used predominantly for viewing digital device screens that have a very different spectral emission profile from the sun.

ZEISS introduced this simple metric because there is no industry standard to quantify blue light blocking in spectacle lenses.


Blue light has a good side, triggering physiological processes that control our body’s internal clock, the circadian rhythm. The circadian rhythm sets our 24 our sleep/wake cycle and is key to our health and wellbeing. Rods and cones are photoreceptors that enable vision under photopic (daylight) and scotopic (nighttime) conditions. Another class of photoreceptors, the intrinsically photosensitive retinal ganglion cells (ipRGCs), do not contribute to vision but detect light intensity, drive pupil aperture control, and other physiological and psychological mechanisms. These specialized retinal ganglion cells play a crucial role in circa dian rhythm, contributing to our wellbeing and sleep-wake cycle. Retinal blue light exposure modulates the hormone melatonin in the ipRGC cells associated with the sleep-wake cycle. The peak sensitivity for melatonin sup pression in the blue light band is around 464 to 490 nm.6 ,7 As a result, blue-light-blocking lens es should transmit these beneficial blue light wavelengths and only block the potentially harmful short wavelength HEV blue light.


With excessive screen use, many people experience digital eye strain. DES symptoms include glare/ dazzle, discomfort, blurred vision, accommodation stress and dysfunction, fixation disparity, pain in or around the eyes, dryness and eye fatigue.8, 9

The Vision Council’s Digital Eye Strain Report and other sources show that more than two-thirds of adults in the U.S. who regularly use digital devices experience symptoms associated with digital eye strain.10

Formerly known as Computer Vision Syndrome (CVS), the contemporary term of digital eye strain includes the plethora of eye and visionrelated symptoms and asthenopia challenges associated with the extensive use of computers and digital displays, intense reading and other extensive near vision tasks. Digital eye strain can occur when the visual demand exceeds the capacity of the accommodation and vergence system to maintain clear and comfortable vision, resulting in an overload of our visual system, leading to eye strain and visual discomfort.


Blue light contributes to digital eye strain, causing symptoms such as blurry vision and visual discomfort.11 Shorter wavelength blue light can induce opto-physical effects while entering the eye on its path through the ocular media to the retina. The two main effects are wavelength-dependent light scatter and longitudinal chromatic aberration.12, 13

The first is linked to the increased scattering (Fig. 4) propensity of short blue wavelengths of light by the ocular media. In effect, intraocular scatter causes “visual noise,” resulting in perceived dazzle, reduced contrast and digital eye strain.

Longitudinal chromatic aberration is also caused by short-wavelength blue light. Because ocular media’s refractive index varies with the wavelength, induced optical dispersion effects can cause longitudinal and lateral chromatic aberrations (Fig. 5). The shorter the wavelength, the higher the refraction angle, giving diverse colors different focal points. For example, the difference between blue and red light can be up to 2 diopters. As a result, the image can look blurred or have noticeably colored edges.


ZEISS BlueGuard is an in-material blue light blocking solution that addresses the complex challenges of balancing blue light’s positive and negative side and is available with ZEISS DuraVision Platinum coating. It blocks up to 40 percent of the blue-violet spectrum14, 400 to 455 nm while transmitting beneficial wavelengths 455 to 500 nm. By blocking blue light in the material, ZEISS BlueGuard reduces digital blue light reflections up to 50 percent compared to typical blue light coatings.15

ZEISS BlueGuard uses the latest benzotriazole and benzophenone-based lens chemistry to support UV and blue light absorption, delivering excellent color fidelity and spectral coverage. In addition, the ZEISS 1.50 index BlueGuard material uses state-of-the-art pigments to balance clarity and protection perfectly. ZEISS uses its global network to deliver ZEISS BlueGuard materials for all standard plastic lenses, indexes 1.50 to 1.74.


As measured by BVB, ZEISS BlueGuard Lenses block up to 40 percent of potentially harmful blue light.14 All ZEISS BlueGuard materials offer similar BVB levels, from 38 percent to 42 percent (Fig. 6) and are available in 1.50, 1.56, 1.60, 1.67, 1.74, Trivex® (1.53) and Polycarbonate (1.59) in many regions.


International regulatory bodies agree that UV is harmful to the human eye and surrounding tissues. Ultraviolet radiation ranges between 100 to 400 nm. While UV is invisible, it can still damage eyes and other structures.

In addition to partially blocking potentially harmful blue light, ZEISS BlueGuard Lenses provide complete UV protection, blocking harmful UV radiation up to 400 nm. This pro tection is standard for ZEISS UVProtect and ZEISS BlueGuard Lenses.


During video calls, lenses with blue-blocking coatings show annoying blue and violet reflections. ZEISS BlueGuard lenses provide superior in-material blue light blocking, reducing blue reflections from the front surface of the lens by up to 50 percent over coatings (Fig. 7).

DBRLED calculates the intensity of blue light reflected by the lens front surface seen by the human eye when the light source is the commonly emitted spectrum from digital screens. In the absence of industry or scientific standards to measure this effect, ZEISS developed the DBRLED metric. Most digital displays produce peak intensity between 380 and 500 nm. Therefore, ZEISS used the display spectrum for the world’s most popular smartphone in the DBRLED calculation.

Based on digital blue reflectance (DBRLED), ZEISS BlueGuard Lenses exhibit up to 50 percent less digital blue light reflection than ZEISS DuraVision BlueProtect.

• R(λ) is the spectral reflectance of the front side of the spectacle lens.

• L(λ) is the Luminous efficiency function for a 10° observer ( htm- CIE 2006).16

• LED(λ) is the spectral distribution of the most popular smartphone of the world 2020[17]

• Because blue light is blocked in-material, ZEISS BlueGuard is ideally combined with ZEISS DuraVision Platinum UV coating—the premium AR coating with outstanding anti-reflective qualities throughout the visible spectrum.

A ZEISS quantitative survey found that 72 percent of participants felt ZEISS BlueGuard Lenses showed less intense reflections than ZEISS DuraVision BlueProtect.18


Previous in-material blue light lenses showed discolorations from grey/blue color additives, reduced lens transmittance and a grey or bluish hue.

ZEISS chemists have found the best balance between clarity and transmission. ZEISS BlueGuard Lenses are engineered to achieve the best clarity and achieve up to 97.8 percent luminous transmittance.14 As a result, 90 percent of wearers are very satisfied with the clarity of ZEISS BlueGuard Lenses.18


The most significant difference between ZEISS BlueGuard Lenses and ZEISS DuraVision BlueProtect is the blue-blocking approach—absorption versus reflection. ZEISS BlueGuard Lenses have an in-material solution in which the blue light is absorbed. ZEISS DuraVision BlueProtect uses a coating, reflecting the light. As a result, ZEISS BlueGuard Lenses are designed to deliver more protection with less reflection and better clarity.


In an external consumer acceptance study19 conducted by ZEISS, 182 participants tested ZEISS BlueGuard Lenses compared to their habitual lenses. Almost 6 out of 10 (59.6 percent) of the study participants were already experienced wearers of various blue filter lenses. The feedback:

• Result 1: 96 percent (9 out of 10) of spectacle lens wearers are satisfied with the clarity of ZEISS BlueGuard lenses.

• Result 2: 93 percent (9 out of 10) of wearers say they feel less digital eye strain with ZEISS BlueGuard lenses.

• Result 3: 92 percent (9 out of 10) of lens wearers state they experience fewer symptoms, including tired eyes, with ZEISS BlueGuard lenses.


• Designed to address digital eye strain by blocking short-wavelength blue light.

• Blocks up to 40 percent of potentially harmful blue light.

• Complete UV protection up to 400 nm.

• Beneficial blue light transmits.

• In-material blue-blocking solution reduces

unwanted digital blue light reflecting off the lens surface by up to 50 percent compared to typical blue filter coatings.

• Optimally balanced for clarity and protection.

ZEISS BlueGuard lenses are a new class of blue filter lenses that offer your patients more protection and less blue light reflections.