effectiveness of consumer blue light filters loewen cavill · 2019-09-17 · loewen cavill,...

Loewen Cavill, 12/11/2018

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Friday 2-5

Effectiveness of Consumer Blue Light Filters

Loewen Cavill

9/6/19 2.671 Measurement and Instrumentation

Friday PM Professor N. Fang


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Abstract Americans on average spend 10 hours and 39 minutes a day on screens. This number has increased by one hour in the last year alone [1]. The unprecedented rise in blue light exposure has drastically increased the prevalence and severity of negative health effects due to blue light radiation. The growing awareness of the “blue light hazard” gave birth to an industry of blue light protection products. The filtering capabilities of these products are not publicly available. A spectrometer was used to measure the spectral intensity of light transmitted through the following filters: four brands of eyeglasses, two software modes and a screen protector. The decrease in intensity of light in the 415nm-455nm range was used to quantify each filters’ effectiveness. The consumer blue light protection eyeglasses performed the worst blocking on average only 12.5% of blue light. The best filters were the industrial eyeglasses blocking 92.5% of blue light.

1. Introduction As we settle into the digital era we have begun to realize the consequences of constant

digital exposure. The constant exposure to the light emitting diodes found in screens has drastically increased the prevalence of ocular damage and sleep disorders due heightened dangers of blue light.

This growing danger is answered by several attempted solutions including but not limited to eyeglasses, software, night settings and plastic filters. As the awareness of the dangers from blue light increase, so do the number of people interested in purchasing blue light blocking products. Before making such a purchase, most ask “Which products best protect against blue light from screens?” However, since these products are so new and varying in nature, this question has been left unanswered for many. The lack of direct numerical comparison of the filters’ effectiveness prevents consumers from getting the protection they desire.

The transmission of blue light across several blue light blocking products were compared in order to inform consumers on the protection provided by each product. A spectrometer evaluated the spectral transmittance of the following products made solely for the filtration of blue light: three brands of consumer eyeglasses, a screen protector, two software modes, and a pair of industrial grade eyeglasses. The direct comparison of blue light transmission across this range of products informs the consumer of the protection provided by different categories of filters as well as across competing brands. OR The direct comparison of this range of filters does not only provide categorical recommendations but additionally informs consumers of the best brands within a given category.

2. Background 2.1 The Increasing Danger of Blue Light

The digital age has drastically increased exposure to blue light turning a subtle danger into a severe one. The widespread adoption and use of blue light emitting screens and lights have created a public health concern centered around industrialized nations such as the United States [2]. The health damage from screen exposure is caused by the high relative intensity of blue light in screens. Natural light only has a small amount of blue light so our eyes have little protection against the historically insignificant danger [3]. Blue light is especially dangerous because it is the highest energy of all the visible lights. Figure 1 illustrates that blue light has the smallest


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wavelength and highest frequency out of the visible light spectrum thus resulting in the greatest danger.

Figure 1: The radiation spectrum depicts that the wavelength of visible light ranges 400nm and 800nm. Blue light has the smallest wavelength and thus the greatest frequency resulting in the highest energy and most dangerous photons out of the visible spectrum [4].

Blue light has shorter wavelengths so it penetrates deeper into the eye. The high

frequency of blue light results in higher energy photons that do greater damage to their surroundings. Equation 1explains how as wavelength (𝜆) decreases the overall energy (𝐸) of the photon increases thus intensifying the damage to the eye. The energy of a photon is equivalent to the Planck’s constant (ℎ) times the speed of light (𝑐) divided by the wavelength.

𝐸 =ℎ𝑐𝜆

Long term exposure to these high energy photons accentuates the dangers of blue light.

The eye has little protection against blue light since until recently, this type of light was only present in small doses. This increased risk, called the blue light hazard, has raised widespread concern due to its health threats [1]. 2.2 Health Effects from Blue Light

Excessive exposure to blue light has been suggested to cause phototoxic retinal damage, eye strain, sleep dysfunction, and even age-related macular degeneration (AMD) leading to blindness [1-3]. Environmental light exposure informs critical circadian rhythms to secrete essential hormones and orchestrate metabolic homeostasis through rod and cone photoreceptor cells specifically triggered by blue light photons [6]. Small amounts of blue light historically served to inform us when to be awake. Night time exposure to blue light through screens has

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perturbed this mechanism by suppress melatonin levels resulting in sleep disorders [1]. Moreover, exposure to blue light causes production of reactive oxygen species (ROS). When the duration of exposure to blue light increases, the body has an overflow of ROS. ROS induces oxidative stress which then triggers photoreceptor and retinal pigment cell death. Studies have shown this oxidative induced cell death may be one of the leading risk factors in age-related macular degeneration (AMD) which is the leading cause of blindness in industrialized nations [2]. So far, the most common way to reduce the risk of such dangers is through blue light filtering consumer products. 2.3 Types of Blue Light Filters

Light filters primarily use one of two techniques: interference and absorbance. Interference filters craft the geometry of the filter and suspend particles in the filter to bounce back light of particular wavelengths. These waves then interfere with incoming light and are reflected back into the atmosphere. These filters glare the color they protect against. In this case, blue light interference lenses appear to have a blue glare when viewed at certain angles [6]. Absorbance filters are the opposite. They appear the complementary color of the light they protect against. These filters absorb the photons of the particular wavelength to be blocked. As demonstrated in Figure 2, a photon of a particularly frequency is absorbed by a compound when the energy required for an electron to transition to the lowest unoccupied electron orbital from the highest occupied orbital is equal to the energy of the photon.

Figure 2: When a photon’s frequency, v, multiplied by Planck’s Constant, h, is equal to the energy difference between the highest occupied orbital and the lowest unoccupied orbital an electron is excited, absorbing the energy of the photon. [7].

A molecule has a unique fingerprint of colors that it absorbs depending on the number of

orbitals and to what extent they are filled. The molecular compound added to blue light absorbing lenses absorb wavelengths between 400-500 nm. Since the entire spectrum of white light enters the film but only blue light is not reflected back, the film appears yellow, blue’s complementary color [8]. A mix of blue light interference and absorbing techniques have been utilized in the creation of a variety of blue light protection products. Historically, the yellow/orange industrial goggles used for intense exposure was main product on the market. However, now since the duration of exposure has increased, a plethora of new protection products have come out. There is software and “night settings” to decrease the intensity of blue light radiating from screens. There are screen protectors that absorb the blue light immediately upon leaving the screen. Even intraocular lenses (IOLs) implanted in eyes now contain pigment that absorb blue light [4]. Most


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recently, there has been a significant trend for millennials to purchases glasses designed to reflect and absorb blue light [1]. These glasses have very subtle color distortion lowering the customer’s inhibition in wearing the glasses in public settings increasing the duration of wear compared to the intense industrial grade yellow/orange goggles that are primarily worn for only more intense short duration blue light exposures. While there has been standards and tests established for the industrial grade blue light protection glasses, there has been little to no study of the effectiveness of protection in these newer, more commercialized products. The significant gap in information comparing different filtration techniques prohibits consumers from making informed decisions of which type of filter provides the protection they need. 2.4 Effectiveness of Protection

A study conducted by Optometry Professor Laura Downie, in 2017 researched revealed that the number of publications about blue light increased by a factor of 10 from the year 2004 to 2009. Since the pervasiveness of the blue-light hazard is so new, the majority of studies focused on determining whether blue light is truly dangerous to the human eye or whether it is speculation [1]. A study out of Gifu Pharmaceutical University compared the type of light with the correlated photoreceptor cell death proving that cell death was indeed the most severe for blue light [9]. A paper in the Journal of Biomedical Optics in 2016 compared the relative transmittance of light at 464 nm and the corresponding cell death. Their experimental results showed there was a direct correlation with the transmittance of the lenses and the rate of cell death, the cell viability and the rate of ROS production. Several studies have confirmed that blue light indeed proves dangerous to the health bringing the question of how we protect against this danger to the forefront.

The same paper out of the Journal of Biomedical Optics went on to compare different types of blocking lenses utilizing different colored pigments and reflective properties. The lenses they tested can be seen in Figure 3. They found the thicker lenses with yellow pigment were the best at protecting the cells from blue light. The pink pigment (h) and antireflective coating proved to be the poorest filters of blue light [2].

Figure 3: Various colored lenses used in this study: (a-h) Are absorbing pigment filters and (i) is a blue light anti-reflective coating lens. The letters (a-i) correspond to their measured protection with the (a) lenses having the most protection and the (i) lenses having the least protection [2].


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The study cited in Figure 3 uses the transmission of blue light to compare the effectiveness of the different materials at filtering blue light. The effectiveness of a filter is typically characterized by its transmittance of a given range of light. A good blue light filter has low transmittance meaning that only a small proportion of blue light passes through the filter. As seen in Equation 2, the transmittance is equal to the intensity of light leaving the sample divided by the intensity of light entering the sample.

Transmittance(λ) =I(λ)𝐼5(λ)

=FilteredIntensity(λ)UnfilteredIntensity(λ)

The measured transmittance of blue light in blue light blocking filters indicates the level of blue light protection for the eye. 2.5 The Gap in Blue Light Studies

Plenty of studies have been conducted confirming that blue light indeed is dangerous to the health. There has been a study out of the Journal of Biomedical Optics that explored the filtering capabilities of different raw materials and pigments [2]. However, where the studies leave off is in the assessment of real products effecting everyday consumers. There is little data or scientific support to the claims made by existing blue light protection products. In the UK, there was significant controversy surrounding the marketing claims made by the blue-light filtering spectacle lenses. The claims were deemed to be “unproven health claims” and were forced to be removed [1]. The lack of analysis around the effectiveness of consumer grade blue light filters makes it extremely difficult for consumers to make an informed decision on how to protect themselves from the dangers of blue light.

3. Experimental Design 3.1 Experiential Setup

In order to evaluate and compare the effectiveness across a series of consumer blue light filtration products, a series of steps were taken to arrive at the percentage of blue light blocked by each filter. For the experimental trials, a 19inch Mac Pro laptop was set at full brightness and placed in a dark room with no ambient light ensuring that the laptop was the only light source. An optical fiber attached to a Vernier SpectroVis Plus Spectrometer. The SpectroVis has an accuracy of ±7.0nm and has an optical resolution of 25nm and reports relative intensities for each 1nm wavelength interval.

As depicted in Figure 4, the optical fiber tip was positioned 7mm from the computer screen with the blue light filter in between. The filters were placed between the optical fiber head and the fully brightened white computer screen. Four runs each with a duration of 15 seconds were conducted for every filter and then averaged together to minimize the error.

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Figure 4: Diagram modeling the experiment setup. The 19inch Mac Laptop at full brightness was used as the LED light source screen. The filters were switched out for each experimental run. The optical fiber head was placed 7 mm away from the screen with the filter in between it and the screen. The optical fiber was then plugged into the Vernier SpectroVis Plus plugged into the laptop to record the data in LoggerPro.

3.1 Filters Evaluated The experiment compared seven different consumer filters from the primary blue light

blocking approaches: eye glasses, screen protectors and software add-ons. The filters were selected to inform the consumer on which type of filter is the most effective at reducing blue light but additionally how the brands compare. All the different blue light blocking techniques were compared. Additionally, amongst the popularized blue light blocking glasses, four of the most common brands were directly compared.


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The following seven filters and control were measured: Control: 100% Bright White Computer Screen, Industrial Grade Orange Computer Glasses, (3) Izipizi Computer Glasses, (3) Pixel Computer Glasses, (4) Felix Gray Computer Glasses, (6) F.lux Sunset Mode, (7) F.lux Night Mode, and (8) 1mm Blue Light Screen Protector.

Figure 5: The four types of glasses tested are pictured above. The Izipizi glasses which ended up working the best out of consumer spectacle glasses can be seen to have a slight yellow-orange tint as well as the industrial grade indicating the two glasses are absorption filters. The three spectacles have a blue glare when angled accordingly revealing the reflective nature of the glasses.

Figure 6: Three software modes at full brightness are compared above. On the left side of the computer no filtration is present, in the center the F.lux Sunset software mode is activated, on the right side the F.lux Night mode is activated. It is apparent that as the intensity of the filter increases the light source appears to increase in its orange hue indicating that less of its complementary blue light is emitted.

Pixel Glasses

Izipizi Glasses

Felix Gray Glasses

Industrial Grade Uvex

Glasses


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III. Results and Discussion The spectral intensity data recorded by the spectrometer was then processed by LoggerPro.

LoggerPro was set to record the relative intensity for wavelengths ranging from 400nm to 725nm. In order improve the resolution and accuracy of the readings, the sample time was set to 100ms and each reading was an averaged over 20 samples. The duration of each experimental run was 15 seconds. Four experimental runs were conducted for each filter type and then the average of the four was used for analysis.

To preform analysis, the relative intensities for each wavelength were exported as a CSV for each experimental run. MATLAB code was developed to process the data and create spectral intensity graphs, transmittance graphs and a percentage of light blocked graph.

Figure 7: In this Power Spectral Distribution, the averaged spectral intensities for each hardware filter are compared. All the glasses and screen protector, are branded as blue light filtering products but only the orange industrial grade glasses show a substantial decrease in the intensity within the blue light range.


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Figure 8: In this Spectral Transmittance graph, the averaged spectral transmittance for each hardware filter is compared. The transmittance was calculated by taking the ratio of the relative intensity of the filtered light to the unfiltered light source across the spectrum. All of the filters have a sharp decrease in transmittance at 436 nm indicating absorbance by compounds with similar electron transitions. The industrial glasses transmit roughly 10% of light in the range of 410nm and 540nm.


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Figure 9: In this Power Spectral Distribution, the averaged spectral intensities for each software filter are compared. Both software modes show a substantial decrease in light intensity up until 590nm.


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Figure 10: In this Spectral Transmittance graph, the averaged spectral intensities for each software filter is compared. The sharpest dips are also centered around 436nm but for the software filters the decreased proportion of light intensity remains relatively constant until 590nm.


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A direct comparison of the filters effectiveness was derived by taking the area under the intensity curve to determine the total amount of blue light radiation remaining after each filtration. MATLAB code utilized the trapz function over the interval 414.24nm-457.68nm to get the total intensity over the range. Then this value was divided by the total light intensity at full brightness to represent the proportion of unblocked light. By subtracting this value from one the proportion of blue light blocked was derived.

Figure 10: The bar graph compares the proportion of blue light ranging from 414.24 nm to 457.58nm that is blocked by the filter. This range was selected due to the fact the blue light hazard zone is typically referred to as light ranging between 415nm and 455nm. The errors were derived from the standard deviations of the filter’s spectral intensity over the repeated trials over this range.

The results show that the Industrial Grade Orange Glasses and the Orange Tinted

Flux Night mode blocked 92.5% and 84.1% of the unfiltered light intensity in the blue light range. The popularized glass spectacles performed far worse barely filtered out blue light. The Pixel glasses performed the worst blocking only 9.0% of the original light intensity. The Izipizi glasses blocked almost double that, but still only blocked 17.7% of blue light. The results for the blue light blocking screen protector also disproved the company’s protection claims. The screen protector blocked 15.4% of the blue light.


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Conclusions The most effective category of blue light filtration products proved to be software add-ons

that vary the blue light emitted from a screen. The glasses divided into industrial and consumer products varied the most in their filtering capabilities with the industrial glasses blocking the most light and the consumer glasses blocking the least light. The industrial glasses blocked 10 times more blue light than the poorest performer, the Pixel glasses.

The results provide strong evidence against the blue light filtering claims of protection for the popularized blue light filtering glasses as well as the stick on blue light blocking screen protector. The orange industrial grade glasses and the orange tinted Night Mode on Flux decreased the intensity of blue light the most supporting the research stating orange absorbance filters work the best at filtering out blue light [2]. This goes to show that the trending blue light filtration products are ineffective at protecting human eyes from the health dangers of the blue light hazard produced by our everyday screens. The increasing prevalence of consumer blue light protecting glasses is not indicative of their protection. These results advice against the purchase of blue light protecting glasses and instead indicate the best filter for the everyday consumer is one of the free blue light protection software add-ons.


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References [1] Downie, L. E., 2017, “Blue-Light Filtering Ophthalmic Lenses: To Prescribe, or Not to Prescribe?,” Ophthalmic and Physiological Optics, 37(6), pp. 640–643. [2] Hiromoto, K., Kuse, Y., Tsuruma, K., Tadokoro, N., Kaneko, N., Shimazawa, M., and Hara, H., 2016, “Colored Lenses Suppress Blue Light-Emitting Diode Light-Induced Damage in Photoreceptor-Derived Cells,” Journal of Biomedical Optics, 21(3), p. 035004. [3] Jaadane, I., Boulenguez, P., Chahory, S., Carré, S., Savoldelli, M., Jonet, L., Behar-Cohen, F., Martinsons, C., and Torriglia, A., 2015, “Retinal Damage Induced by Commercial Light Emitting Diodes (LEDs),” Free Radical Biology and Medicine, 84, pp. 373–384. [4] Filimon_K (2017). Materials/\ Instructable for Blue Light Sensor. [ebook] Available at: https://publiclab.org/notes/filimon_k/12-14-2015/materials-instructable-for-blue-light-sensor [Accessed 27 Sep. 2018]. [5] Tanito, M., Sano, I., Okuno, T., Ishiba, Y., and Ohira, A., 2018, “Estimations of Retinal Blue-Light Irradiance Values and Melatonin Suppression Indices Through Clear and Yellow-Tinted Intraocular Lenses,” Retinal Degenerative Diseases, J.D. Ash, R.E. Anderson, M.M. LaVail, C. Bowes Rickman, J.G. Hollyfield, and C. Grimm, eds., Springer International Publishing, pp. 53–60. [6] “Interference - Non-Reflective Coatings: Physclips - Light” [Online]. Available: http://www.animations.physics.unsw.edu.au/jw/light/non-reflective-coatings.html. [Accessed: 27-Sep-2018]. [7] Visible Spectroscopy. (2014). [ebook] Irvine: University of California, Irvine. Available at: http://faculty.sites.uci.edu/chem1l/files/2013/11/RDGVISSpec.pdf [Accessed 27 Sep. 2018]. [8] “Absorbing Light with Organic Molecules” [Online]. Available: http://butane.chem.uiuc.edu/pshapley/GenChem2/B2/1.html. [Accessed: 27-Sep-2018]. [9] Kuse et al., “Damage of Photoreceptor-Derived Cells in Culture Induced by Light Emitting Diode-Derived Blue Light.”

Acknowledgments The author appreciates the constant support of Dr. Barbara Hughey, Thalia Rubio, and Dr. Nicholas Fang. A special thanks to Justin Xiang and Selin Selman for lending their glasses for testing.

effectiveness of consumer blue light filters loewen cavill · 2019-09-17 · loewen cavill,...

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