48 color blind people participated in this research, carried out at the UGR Department of Optics, after a public call to which more than 200 volunteers responded

The EnChroma® glasses, commercialized by a North American company, do not improve color vision for color blind people or correct their color blindness, and their effect is similar to that of other glasses such as the ones used for hunting

48 color blind people participated in this research, carried out at the UGR Department of Optics, after a public call to which more than 200 volunteers responded

One of the authors of this research is also color blind, and he carries out his research in the field of color vision

The recent commercialization of theEnChroma®glasses has generated great expectations among the color blind thanks to a strong campaign in social networks and media. They hoped to see new colors or even correct their color blindness by using said glasses.

The North American company manufacturing them advertises an improvement in color vision for certain types of color blindness, protan and deutan, by extending the range of colors perceived by the subject without affecting the colors that are already distinguished without glasses. In fact, on their website,EnChroma®states that their glasses "alleviate red?green color blindness, enhancing colors without the compromise of color accuracy" but claiming that their glasses "may not work" for severe red?green deficiency.

One claim on the company's website (at least until October 2017) was that their glasses "are designed to improve the everyday experience of color vision". However, that claim has been recently substituted by a more subtle sentence: "the glasses are an optical assistive device for enhancement of color discrimination in persons with color blindness; they are not a cure for color blindness", pointing out that "results vary depending on the type and extent of color vision deficiency per individual."

In an article published in Optics Express, one of the most relevant journals with a great impact in the field of optics, researchers from the University of Granada (UGR) have debunked the effectiveness of these glasses for color vision deficiency (CVD), proving that theEnChroma®glasses don't make color blind people's vision comparable to that of people without color blindness.

A study with 48 color blind volunteers

This UGR research has counted with the participation of 48 people with color blindness, after a public call to which more than 200 volunteers responded. The researchers have used, for the first time, two complementary strategies in order to evaluate the effectiveness of the glasses. The first strategy consisted in evaluating the color vision of the participants with and without glasses using different types of tests: the Ishihara test (recognition) and the Fansworth?Munsell test (arrangement). Besides, they have added a test based on the X?Rite Color Chart, which evaluates subjective color naming.

The second approach for evaluating the effectiveness of these glasses consisted in using the spectral transmittance of their lenses to simulate different observers, which allowed to evaluate the changes in color appearance.

According to Luis Gómez Robledo, professor from the UGR Department of Optics and one of the authors of this paper, "normal human color vision is trichromatic thanks to a cluster of three types of photoreceptors known as cones, which are present in the retina. These cones are sensitive to short wavelengths (S), medium wavelengths (M) and long wavelengths (L). However in Europe, about 8% of men and 0.5% of women in the Caucasian population suffer from some type of congenital anomaly in the performance of some of the cones, which causes color vision deficiencies. This anomaly is a sex?linked recessive trait, with the red?green color vision deficiency being the most frequent in humans." Said red?green CVD is in turn classified into two types:protan and deutan, depending on the affected cones. Moreover, there is another classification based on the severity of the deficiency: protanomalous or deuteranomalous, and protanopic or deuteranopic.

Glasses similar to those used for hunting

This study carried out by the UGR shows that a color blind person using theEnChroma®glasses will not perceive new colors, but rather the will see the same colors in a different way.

"This makes possible for some individuals using these glasses to distinguish some colors, but to the detriment of others which will be now confused. Even though a color filter as that used by theEnChroma®glasses may change the appearance of colors, it will never make color vision more similar to a normal observer's vision," the authors state.

The effect of using theEnChroma®glasses is similar to that achieved with glasses designed for specific activities (shooting, hunting, low eyesight etc.), where the use of colored glasses helps to better perceive certain stimuli thanks to an increased contrast with the surroundings.

Besides, during the research, the observers were asked to look at their surroundings with the glasses and to subjectively assess the possible improvement. None of the participants noticed any improvement to the colors of their surroundings when looking through the glasses, except for just one female participant with very mild deuteranomaly.

The results show that the glasses specifically used in this study have not revealed any improvement in the two types of color blindness tests: recognition and arrangement.Therefore, the glasses cannot help in cheating in professional screening tests, in agreement to what the company claims on its website.

The group of researchers, all of them belonging to the Department of Optics at the Faculty of Science of the University of Granada, is integrated by doctors Luis Gómez Robledo, Eva Valero Benito, Rafael Huertas Roa, Miguel Angel Martínez DomingoandJavier Hernández Andrés. It is worth mentioning that one of them, Luis Gómez Robledo, is also color blind, and he carries out his research in the field of color vision.

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