Blue light-absorbing glasses can impair color vision, University of Granada study finds

A pilot study by scientists from the University of Granada (UGR), part of the Color Imaging Laboratory of the Department of Optics, has shown that glasses marketed to absorb blue light from mobile phone screens can impair vision colors in some people.

The blue light emitted mainly by screens (mobile phones, tablets, TVs, etc.), as well as LED lights and other electronic devices, has received a lot of attention. media attention in recent years, creating controversial alarm among the population about its possible effects. Despite the lack of solid scientific evidence proving the risk of blue light for retinal cells, some companies decided, ten years ago, to manufacture filters that “block” blue light. They are marketed, for example, as screen protectors for computers, mobile phones or tablets. although these electronic devices also usually incorporate functions that allow the user to change the intensity and color temperature of the screen by dimming the emission in the blue zone, such as when using the popular night mode .

The most common use of blue light “blocking” filters is as added protection incorporated into contact lenses, ophthalmic lenses or intraocular lenses. Today, virtually all manufacturers of these products offer the option of blue light protection. A majority of users choose to integrate these filters when purchasing their glasses or contact lenses, with the consequent increase in price, as they have been warned of the possible “risks” of blue light in many marketing campaigns. However, optometrists sometimes encounter users who reject this type of filter because they have found that it affects performance in their professional activities, in which color perception is essential, such as graphic artists, tattoo artists, dental technicians, etc. or lighting designers. , among other examples.

Scientists from the UGR Optics Department developed an 8-month pilot study to investigate how long-term use of filters marketed as “blue light blockers” could alter color perception, and describe the time course possible changes. To do this, they analyzed 8 filters from 5 commercial brands and performed psychophysical experiments on a group of 18 observers with normal color vision, and an additional control group of 10 observers not using any filters.

Three different tests were used to assess changes in color perception: the Farnsworth Munsell 100 test, the Color Assessment and Diagnosis (CAD) test developed by the City University of London, and a test specially designed at UGR to measure the degree of chromatic adaptation. participating subjects. The 18 observers wore the glasses with the blue light filters for two weeks continuously.

The first surprising result (after measuring the spectral transmittances of the filters in the range from 380nm to 500nm, which is the range corresponding to blue light), is that none of the 8 filters analyzed, despite the fact that they are sold as filters”blockers” of blue light, they absorb more than 40% of blue light (as can be seen in the attached graph, where the spectral transmittance of each filter is indicated, which is the percentage of light that passes through the filter).

Most of the filters analyzed only block a small region of 380-400 nm, which corresponds to the ultraviolet range, but they allow close to 80% of blue light to pass, around 440-450 nm, where the blue light is located. maximum emission. pic of blue LEDs used in digital device screens. Even the filter, out of the 8 analyzed, which absorbs the most in these wavelengths, allows more than 65% of blue light to pass. For the blue LED emission peak, the absorption average of the 8 filters analyzed is only 19%.

Additionally, this pilot study shows that there is a slight worsening of color discrimination in the blue/yellow area. The high variability of the results according to the observer supports the fact that the acceptance of the filters by the customers who buy them varies according to the individuals. The scientists responsible for this pilot studywhich was published in the scientific journal Express OpticsThey are currently continuing this research.

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