CitationCarlson AS. A comparison of blue-light transmissions through blue-control lenses. Afr Vision Eye Health.

1. Blue Control License Number Massachusetts

2019;78(1), a497.Original ResearchA comparison of blue-light transmissions through blue-control lensesAnthony S. CarlsonReceived: 22 Jan. 2019; Accepted: 14 Aug. 2019; Published: 30 Oct.

2019Copyright: © 2019. The Author(s).

Licensee: AOSIS.This is an Open Access article distributed under the terms of the, which permits unrestricted use, distribution,and reproduction in any medium, provided the original work is properly cited.AbstractBackground: Many people are exposed to blue light through devices such as cellular phones, tablets and computers. Such light may affect us depending on its wavelength and blue-control lenses are now frequently used, thus influencing our daily lives.Aim: This study provides an analysis of the transmissions of blue light through 10 lenses with different blue-control coatings.Setting: The study was conducted at the Department of Optometry, University of Johannesburg, South Africa.Methods: Transmission curves of 10 lenses with different blue-control reflective coatings were compared. A control lens (the achromatic lens) was also included.

The Cary Varian 5000 photo spectrophotometer from the Department of Physics at the University of Johannesburg was used to measure the spectral transmittances of these lenses with refractive indices ranging from 1.5 to 1.6. The geometric centre of each lens was aligned with the measuring axis of the spectrophotometer and spectral transmittance between 300 nm and 500 nm was measured.Results: For the 10 lenses studied, the transmission of wavelengths below 460 nm varied from 48% to 69% and for wavelengths between 460 nm and 500 nm from 33% to 55%. The differences between lenses were greater than 20%. If we changed the range of transmission to between 480 nm and 500 nm, the percentage transmitted varied from approximately 71% to 83% to give about a 12% difference between all the lenses.Conclusion: Not all lenses displayed similar transmissions of blue light and different manufacturers do not agree as to what percentage of blue light should be reflected or transmitted.Keywords: blue light; transmission; reflective coatings; cumulative curves; normalised cumulative curves. IntroductionVisible light is that part of the electromagnetic spectrum that ranges from approximately 380 nm to 760 nm in wavelength.

Blue light is the radiation that ranges from about 400 nm to 500 nm. Wavelengths ranging from approximately 400 nm to 460 nm are believed to be harmful to the human eye. Recent research has found that light of this band triggers critical physiological responses, including pupil constriction and circadian rhythm synchronisation. Blue light of this wavelength cannot be absorbed by the cornea or crystalline lens and is transmitted directly to the retina.

Excessive blue light of 400 nm – 460 nm may cause damage to the crystalline lens proteins and account for cataracts, accelerate the degeneration of retinal pigment cells and increase the acidification of retinal cells. In vitro studies done on animals have shown hazardous effects of blue light in ageing eyes through the accumulation of lipofuscin, which is commonly known as ‘the age pigment’ within the retinal pigment epithelium (RPE). The exposure to artificial light at night not only influences sleeping patterns, but also causes weight gain, depression, cancer and heart disease.

The American Medical Association issued a statement claiming that bright light emitting diodes (LED) lights are causative components of chronic disease risks. The specialised cells in the retina respond to the shorter wavelength light that affects the circadian rhythms.

As these cells are stimulated, the brain is awoken, decreasing melatonin levels and driving out drowsiness, due to hormones such as cortisol and ghrelin being produced.These wavelengths range between approximately 380 nm and 500 nm. The blue-light hazard function peaks at about 435 nm – 440 nm.

Light emitting diodes (LED) bulbs and various other devices also peak at about the same wavelengths. Therefore, a reduction of these wavelengths is the most efficient way of reducing the potential effects of blue light.Nowadays, the human eye is potentially exposed to excessive amounts of the harmful, shorter wavelength blue light through digital devices such as tablets, computers, cellular phones, LED bulbs and all other artificial light sources emitting this type of light.

However, the level of blue-light exposure from computer screens and other LED-emitting devices is less than the level of blue light exposure from daily light. Nevertheless, blue light from these digital devices suppresses melatonin by 23%. The use of longer wavelength light definitely has less influence than that of ‘blue light’ and is recommended for use at night.

Avoiding blue light for 2 h – 3 h before bed helps the body prepare better for improved sleep. State that the reduction of blue light also lessens eye fatigue and dry eye symptoms. Apart from minimising this light, the bright light that we are exposed to during the day should be maximised.Light emitting diodes (LEDs) are said to produce retinal damage especially if correlated with colour temperatures that exceed 3000 K as they generate a greater short-wavelength energy. Bullough et al. Concluded that there was insufficient evidence that there is retinal damage from long-term exposure to LED light as it does not reach the threshold of a blue-light hazard. Apart from the digital devices mentioned, the greatest source of blue light is sunlight. Although exposure to our devices is somewhat less than that from the sun, it is potentially damaging.

While too much sun exposure can increase the risk of certain disorders such as cataracts, growths in the eye and cancer, not having enough exposure to the sun is also detrimental. When children do not have enough exposure to sunlight it affects the growth and development of the eye and can increase the risk of myopia.Potential toxicity of excessive blue light on our vision motivated optical companies to manufacture blue-blocking coatings and filters in ophthalmic lenses and intraocular lenses (IOLs). They are designed to protect our eyes from photochemical damage and alleviate the risk of retinal toxicity by blocking, or weakening, the shorter, harmful blue-light wavelengths. These lenses use filtering materials or surface coatings to reduce the transmittance of these hazardous wavelengths. The Alcon AcrySof Natural Intraocular Lens was one of the first blue-control IOLs developed.Leung et al.

Revealed that devices that companies are producing have blue-control coatings that offer 10% reflection of more harmful blue light with shorter wavelength and 90% transmittance of the less harmful longer wavelength blue light. Vimont states that Dr Khurana suggests that the best way to protect one’s eyes from eyestrain from the blue light emitted from devices is by using the ‘20-20-20’ rule which implies taking a break every 20 min to look at an object 20 feet away for 20 seconds. Vimont claims that due to the lack of evidence that a blue-control lens works to protect your eyes against blue light, the use of special eyewear is not recommended.Efforts have been made to develop prophylactic and therapeutic methods to protect retinal cells from phototoxic damage in cataract surgery. A yellow intraocular lens that blocks both UV and blue light (. Data analysisTo perform this analysis we constructed, for each transmittance curve, a new curve called the normalised cumulative integrated transmittance curve (NCITC). Before constructing this curve, we first had to construct a cumulative integrated transmittance curve (CITC) I (λ) that sums the area beneath the transmittance curve from the lowest point on the interval of interest up to the λ of interest,where x is the wavelength of a data point on the transmittance curve T( x), with x less than or equal to λ, and d x is the increment between x and the next wavelength measured.The total integrated transmittance (TIT) is I( λ max) where λ max is the largest wavelength on the interval of interest.

In that way, we then integrated the amount of light transmitted by each lens on the entire interval of interest. This number is neither an intensity nor a percentage because it carries units that are different from intensity and percentage.

We then used this number to compare the transmittance of one lens against any other lens. Using this number, we constructed an NCITCThis normalisation re-scales the CITC and preserves its shape.

By definition of N( λ), this curve carries no units. Therefore, each point on an NCITC corresponds to a fraction of light transmitted by a specific lens below some wavelength λ. For example, if a point on the curve N( λ) = 0.5 lies above the point on the λ on the x axis below which 50% of all transmitted light is transmitted. Similarly, the point N( λ) = 1.0 lies above a point λ on the x axis below on the interval of interest below which 100% of all wavelengths incident on the lens is transmitted. Therefore, the TIT together with the NCITC characterises the transmittance of a lens and facilitates the direct comparison of lens transmittances.For a given lens, we construct a 50% transmission band, centred at the expectation value of E λ. This is the total integrated weighted transmission divided by total integrated transmission and is calculated byThe lens transmits on the interval at this average wavelength. We can then construct a 50% transmission band about this point.

The band is centred at the 50% point on the normalised cumulative curve. Consider wavelengths α and β such that N( α) = 0.25 and N( β) = 0.75. Then N( β) – N( α) = 0.5. This means that 50% of the total integrated transmission through a lens occurs on the band from α to β.

This band contains E λ. We call this the 50% transmission band and it characterises the transmission of a given lens on the interval of interest. We consider the position and width of this band among all lenses we included in this study. In particular, we consider the relative positions of E λ within each band and the overlap of this band with the ‘bad blue light’ band (400 nm – 460 nm) and the ‘good blue light’ band (460 nm – 500 nm) – see. Ethical considerationsThis article followed all ethical standards for research without direct contact with human or animal subjects.

ResultsAccording to the results obtained, transmittance values from the front and back surface of all the lenses were approximately equal; therefore, only transmittance for light entering from the front surfaces was considered. And show the transmittance curves for all lenses ( N = 11) tested. These curves show the light transmitted for each wavelength independently. The plots show the transmittance of the incident radiation transmitted on a range of wavelengths (300 nm – 500 nm). And show the cumulative plots (from ) for all lenses, indicating the area of the light transmitted beneath the transmission curves for each lens in from the lowest point on the interval up to 500 nm. This number is neither an intensity nor a percentage because it carries units that are different from intensity and percentage. We use this number to compare the area transmittance of one lens against any other lens.

Shows the area as a number for each lens from the lowest on the transmission curve to 500 nm. The measurements have been categorised from the lowest wavelength to 460 nm and then the total area under the transmittance curve. Wavelengths from where each interval starts up to 460 nm represent the harmful blue light and wavelengths from 460 nm to 500 nm represent the good blue light. And show the normalised cumulative plots (from ) showing the transmittance of light beneath the transmittance curves in over a range of wavelengths for all 11 lenses. From, we can see a 50% transmittance band across two wave bands of light that is transmitted over a range of wavelengths. This is shown in.

Consider, for example, an arbitrary curve in for wavelengths α and β such that N( α) = 0.25 and N( β) = 0.75. Then N( β)–N( α) = 0.5. This means that 50% of the total integrated transmittance through a lens occurs on the band from α to β.

This band contains E λ (see ). DiscussionThe achromatic lens was used as a control lens as it does not have any blue-control properties, but only an antireflection coating. When looking at we observe that wavelengths less than 360 nm are not being transmitted by the control lens nor any of the other blue-coated lenses. Hoya, I Relief and achromatic lenses begin their transmissions of light only from wavelengths of about 360 nm – 370 nm.

Blue Control License Number Massachusetts

For the other lenses transmissions begin between wavelengths of 390 nm and 415 nm. Blue light ranges from approximately 400 nm to 500 nm with the more harmful being between 400 nm and 460 nm.represents the area of the light transmitted under each curve in and is represented by a number for wavelengths ≤ 460 nm (shorter) to where the transmission starts as well as for wavelengths between 460 nm and 500 nm (longer). The achromatic control lens has the largest area beneath its transmission curve (118) followed by the Shamir Blue Shield (112), i-Relief (111) and then the Hoya Blue Control (110) which all have values greater than 100. Shamir Blue in mass (70) has the smallest area followed by the Kodak and GKB (74).

This is followed by Prevencia (79), Zeiss Blue Protect (80), Shamir Glacier (84) and then the MR Blue Coat (88). It can be seen that the lenses showing the smaller areas also have a smaller range.

The first number in the brackets in represents the shortest wavelength whereby transmission begins.For wavelengths ≤ 460 nm, from we see that the control lens (achromatic) has the largest area for wavelengths ≤ 460 nm (80) followed by Shamir Blue Shield (74). The Shamir Blue in mass has the smallest area (32) followed by the Kodak in mass (35) and then the GKB (36). The rest are then followed by Zeiss Blue Protect (42), Preventia (43), MR Blue Coat (48), Blue Glacier (49), Hoya (53) and then I Relief (55).represents the transmittance of radiation at wavelengths ≤ 460 nm to where the transmittance starts as well as for wavelengths between 460 nm and 500 nm for each lens type.

From we see that the control lens (achromatic), Hoya and I Relief transmittance is similar for the shorter and longer wavelengths (0.67, 0.66, 0.69 and 0.33, 0.34 and 0.31 respectively) when compared to the other lens types. These lenses also transmit more UV light as they start transmitting from approximately 360 nm – 370 nm.

Shamir Blue Zero in mass, GKB and the Kodak in mass transmit the lowest for the shorter wavelengths (0.46, 0.48 and 0.48 respectively) and the highest for the longer wavelengths (0.54, 0.52 and 0.52 respectively). Preventia (0.54), Glacier Blue (0.58), Zeiss Blue Protect (0.52) and MR Blue Coat (0.57) transmit more for the shorter wavelengths than the in mass lenses, that is, Shamir Blue Zero, GKB and Kodak but transmit less for the longer wavelengths, 0.46, 0.42 and 0.48 respectively.

When comparing the achromatic to the Blue Shield, I Relief and Hoya, they all transmit approximately the same amount for the shorter and longer wavelengths (0.67–0.33) respectively. However, only the Blue Shield cuts out all of the UV radiation. Research done by Tosini et al. Stated that exposure to blue light in the range of approximately 400 nm – 470 nm causes damage to photoreceptors and RPE cells. Reported that LED devices emitting light at 456 nm and 553 nm impose more damage to retinal cells, while blue light in the range of 470 nm – 490 nm is essential for physiological functions.

Ironically, these wavelengths overlap; however, certain LEDs do emit these wavelengths.Studies done in London by Lawrenson et al. Concluded that there is no significant difference in the improvement of macular health with intervention of blue-blocking control spectacles. They further picked up that these blue-light blocking lenses affect visual performance like colour vision and contrast sensitivity.

They also found that there appears to be no significant benefits of these blue-blocking lenses in improving visual performance and protecting macular health from macular degeneration when compared to normal uncoated spectacle lenses. One study, however, reported a small improvement in sleep quality in people with self-reported insomnia after wearing high compared to low blue-blocking lenses. A study involving normal participants found no observed difference in sleep quality. However, some patients wearing blue-coated lenses reported that they provide better anti-glare performance and improve their vision for computer and mobile digital screens.

In conclusion, they suggest that blue-coated lenses should serve as a supplementary option for protecting the eye from potentially harmful blue light but do not guarantee a 100% protective effect.One possible limitation to our study was that we could not assess the effects of these blue-control lenses on participants in order to determine which coating proved most effective. The higher the percentage of transmission for wavelengths shorter than 460 nm, the greater the transmittance of blue light through the coating. This implies that there is more risk of exposure to the hazardous effects of blue light on the human eye, and potentially more risk of destruction of the retinal pigmented epithelium (RPE) which can further cause visual impairment such as ARMD. Laboratory studies have shown that reducing blue-light transmission of wavelengths of 430 nm through a blue-light filter by 50% could reduce approximately 80% of photochemical damage to the retina.

ARMD, however, is a multi-factorial eye disease. It has risk factors that include age, smoking, nutritional status, exposure to sunlight and genetic background and cannot be theoretically based on blue-light transmission alone. There appears to be conflicting opinions and results among researchers; therefore, further research needs to be done on this topic. ConclusionThe transmittance of radiation for wavelengths ≤ 460 nm varied from 46% to 69% and between 460 nm and 500 nm from 31% to 54% among the 11 lenses.

The differences appear to be greater than 20%. If we changed the range to between 480 nm and 500 nm, the transmittance varied between approximately 71% and 83%, giving about a 12% difference between all lenses. It appears that the companies differ slightly in opinion as to what percentage of blue light should be transmitted. Acknowledgements Competing interestsThe author has declared that no competing interests exist. Authors’ contributionsI declare that I am the sole author of this research article. Funding informationThis research received no specific grant from any funding agency in the public, commercial or not-for-profit sectors. Data availability statementData sharing is not applicable to this article.

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