Is it true that the dark theme of the screen on electronic devices is more useful for vision?

The use of a dark theme on the screen of a smartphone or tablet is considered more preferable and sparing for vision than the active in default bright. We decided to check if there are scientific data that reinforces such a belief.

Dark The topic is all wider It is used in mobile and desktop applications. Developers called among its important advantages less voltage vision. Some advertising campaigns of a dark topic emphasize Attention on the fact that she can increase User concentration, improving tasks. Another argument In favor of a dark topic Consistent The fact that its use before bedtime allegedly reduces the amount of light that comes into the body, which negatively affects the production of melatonin, and therefore will improve the quality of sleep. Technological Giants on their own resources For developers Lay out whole guides to develop a dark topic in applications.

Although different terminology is used in different applications, in this text we will call a dark theme or dark style the display of the application interface with a dark background and light letters, and a light theme and light style - respectively, a traditional display of dark letters on a light background. Two more concepts will also be used - “night mode” and “day mode”, these terms will indicate a decrease in the brightness of the screen with filtering blue light and, conversely, its increase. This function is available for automatic adjustment depending on the time of sunset and dawn on many mobile and desktop devices.

In order to begin to understand how the bright and dark themes of applications affect vision, you must first understand how the eye works and how we see the world around us. Items They become visible only when elementary particles of light fall on them - photons. Photons can be reflected from the subject or it can emit them himself. In the retina of the eye are located Special photosensitive cells on which photons fall. These cells transmit electrical impulses through a chain of neurons to the brain, which thus recognizes the image. Black color, as you know, absorbs light, and white, on the contrary, reflects. In the case of a bright topic, it would be more correct to say that we see not the letters of the text, but the gaps between them. In the case of a dark theme, we see the letters, that is, light elements on a dark background.

To describe the contrast between the background and text, the term “contrast polarity” is usually used. It is positive and negative. Positive contrasting polarity is the location of dark objects on a light background (with a light theme of electronic devices or when reading a regular book). Negative contrasting polarity is just the same dark topic, the perception of light letters from the dark background. And although the dark topic has gained popularity in recent years (for example, for iOS it appeared in 2019, and for the desktop version of VKontakte - only In 2022), to consider it a novelty would be incorrect. Prior to the appearance of visual shells of operating systems, monitors with an electron-ray tube worked mainly in the mode of negative contrast polarity-for example, green letters on a black background. Therefore, one should not be surprised that studies on the influence of positive and negative polarity on the organs of vision began to be carried out long before the dark theme became a trend on digital devices.

So, back in 1997, scientists from the State University of Stephen F. Austin (Texas) set out to determine which combinations of the color of the background and text, as well as the font and drawings, users of websites perceive best of all. To do this, scientists suggested 42 volunteers to find a given word on Internet pages made in different style. Volunteers participating in the experiment is best distinguished Black letters placed on a white or gray background, the rest of the combinations caused some difficulties. It is funny that the authors of the study that placed the results of research on their website chose a light yellow background and green font.

In 2013, in the scientific journal Ergonomics Published The article "The positive polarity of the display is favorable for both young and older people." Scientists from the University of Henry Heine (Germany) invited volunteers with normal or adjusted to normal vision of two age groups: from 18 to 33 and from 60 to 85 years. At first, they were offered a test for visual acuity - a Golovin table, which can be found in almost any office of ophthalmology next to a more familiar Sivtsev table, among the people often called “ShB” in the top of the upper line. Unlike the Sivtsev table, the Golovin table does not use letters, but the open figures - the rings of the landolt, the rupture of which is directed up, down, to the right or left. This alternative table is used when the doctor has a suspicion that the patient has learned the Sivtsev table, or when the patient does not speak Russian.

The Golovin table was presented to the participants in two versions: each got one version either with positive polarity or with a negative one. Both a group of young and a group of elderly patients distinguished gaps on the first version of the table, with black rings on a white background. In the second task, the participants were asked to subtract the text, that is, to find errors in a small fragment, also printed in two versions. And again the bright topic “won”, and with an even greater margin than in the task of visual acuity. In the final of the experiment, the participants were asked to evaluate their own fatigue, namely eye tension, headache, muscle tension, back pain and subjective well -being. No differences between the answers of those who got tasks with positive polarity, and those who performed them with negative polarity could not be found. 

In 2017, American scientists decided In detail to study the connection between the readability of the text with its polarity and size. Volunteers again completed the task of dismembering of the text in different polarities. Researchers came to the conclusion that the smaller the text, the greater the advantage of the bright topic. At the same time, the volunteers themselves did not report the differences in assessing the readability of the text, that is, it was equally comfortable for them to look for typos in both the bright and dark topic, while their results were distinguished. Scientists explained the advantage of a bright topic by the fact that in bright light the pupil narrows, and this reduces Spherical aberrationthat we perceive as blurring of the text.

In the same experiment, scientists tried Understand which topic will show itself better in conditions of high and low illumination. To do this, they brought to the screens of computers the task of a lexical solution - the volunteer demonstrated the sequence of signs for a short period of time, and he had to understand whether this was a word or not. In lighting that imitates daytime, no topic had significant advantages, and with imitating the night - the bright topic won again, since with modeled night lighting and a dark topic, volunteers perceived the small text much worse. Interestingly, the modeled daytime also increased the decision -making speed. As a result, the bright topic turned out to be more universal.

From these studies, we could conclude that the bright topic is definitely better, and install it in the settings once and for all. However, it is important to remember that all the described studies were focused only on the perception of the text and the well -being of the participants exclusively within the framework of a short -term experiment. The longest consequences of the constant use of a particular topic devoted their work Scientists from Tubingen University in Germany. For the experiment, they invited seven volunteers who read the text on the screen with a light or dark theme within an hour. Then with the help optical coherent tomography Scientists measured the thickness of the choroids, the vascular shell of the eye, whose thinning is an important predictor of myopia (myopia). In just an hour of reading a bright text on a dark background, Horioida thinned out by 16 microns, and over the same hour of reading in a negative contrasting polarity, it became 10 μm thicker. Scientists recognize the limitations of the data obtained - a small sample, obscure prospects for changing the thickness of the eye shell after the end of the test, the effect of stress from the use of an unusual contrast mode - but recommend more research on the possible positive effect of reading with a dark theme on the inhibiting (inhibiting) of myopia.

At the same time, users with vision pathologies that arose due to a violation of the transparency of the optical media of the eye (for example, with cataracts), a dark theme Maybe give advantage In distinguishing the letters. Presumably, this effect occurs because the bright theme allows you to get into the eye of a larger amount of light and potentially creates more distortions. 

Finally, another argument in favor of a dark topic - its use in the evening allows you not to overload the body with light, which slows down the production of a sleep hormone Melatonin. The use of digital devices with a bright screen late in the evening can really worsen the quality of night rest, and experts Consult Do not use a smartphone or computer two hours before bedtime. Modern electronic devices, in addition to the dark topic, also offer a night mode, in which the brightness of the screen is reduced, which should, in turn, reduce the negative impact blue Sveta - The most destructive For melatonin. Unfortunately, American scientists based on the results of experiments They came To the conclusion that such a measure is ineffective: a screen that works in normal and in the night, equally reduced the production of melatonin. So the night regime can be considered a marketing course rather than a working tool for protection against the harmful effects of electronics before bedtime.

Thus, scientifically proven advantages in a dark topic are only for people with visual impairments caused by clouding of the optical media of the eye. Perhaps, in the long run, the constant use of a dark topic can slow down the development of myopia, but so far the scientific data is not enough for such a conclusion. In addition, at night, this approach reduces concentration and complicates the recognition of small elements. A traditional bright topic improves the perception of the text in people of all ages. Also, it is hardly a significant argument in favor of the dark topic that it does not so destructively affect melatonin. Even modes with reduced brightness yet cannot level the harmful effects of blue. At the same time, with the exception of some loss of attentiveness, no negative effect on health was found in a dark topic. Therefore, if you visually like a dark topic more, you can safely use it.

Image on the cover: Popular science

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