Unexpected Causes Why people become shortsighted by reading

Simple strategy for myopia: read white on black

According to health experts, over 40 percent of Germans are short-sighted and need visual aids. It is expected that the number of people with myopia in the coming years will increase massively. But something can be done about it: researchers have now found that a very simple strategy could help counter the development of myopia.

Increase in myopia

Two years ago, researchers from Singapore and Australia reported on a study that found that half of the world's population will be nearsighted by 2050. In Germany too, the number of nearsighted people is very high: According to a study by the University of Mainz, more than half of high school graduates and university graduates suffer from nearsightedness (myopia). But something could be done about it: Scientists from Tübingen have now found that a very simple strategy can help prevent myopia.

More and more people are short-sighted and need glasses. Researchers have now found that a simple strategy can help prevent myopia. (Image: ivanko80 / fotolia.com)

The educational level is crucial

Ophthalmologists are assuming a significant increase in myopia over smartphones. Because the permanent close work is responsible for myopia.

In addition, it is known from previous studies, "that a high level of education is often associated with the development of myopia," as Professor Dr. med. Norbert Pfeiffer, director of the Eye Clinic and Polyclinic of the University of Mainz explained in an earlier communication.

The expert had also studied with colleagues, whether myopia can be a consequence of intelligence.

At that time, the researchers concluded that, in this context, the level of education of a person rather than his or her intelligence is primarily critical to the development of myopia.

Many smart people have a visual aid

Why many smart people wear glasses is also related to the fact that they usually read a lot. But why does reading actually make you short-sighted??

The scientists Andrea C. Aleman, Min Wang and Frank Schaeffel from the Ophthalmology Research Institute at the University Hospital Tübingen have now gained new insights.

They derive a surprisingly simple strategy against the development of myopia. In the journal "Scientific Reports Nature" they report on their research results.

Myopia is the price of good education

As explained in a statement from the University Hospital Tübingen, the eye grows too long in myopia, the image is sharply imaged in front of the retina and one sees in the distance out of focus.

Short-sightedness is therefore the price for good training: per year training is about a quarter of a diopter shortsighted on average. Worldwide, myopia is on the increase, because good education is always more important, say the experts.

It has been reported that myopia affects children who spend a lot of time outdoors in the open air before going to school later in life.

However, when children read a lot during their training, the risk of developing myopia increases.

Visual information is massively reduced

According to the experts, there is still no clear understanding of what exactly makes children short-sighted when reading.

It has long been believed that too little reading accommodation places the sharp image behind the retina, causing the retina to grow faster. However, these data were never completely convincing.

Andrea C. Aleman, Min Wang and Frank Schaeffel from the Ophthalmology Research Institute at the University Hospital Tübingen have now found an unexpected reason why reading could be shortsighted.

Unlike a digital camera, which reads every pixel, the retina measures mainly differences between neighboring "pixels", the photoreceptors, it explains in the message.

This is achieved by comparing the brightness of the cells in the center and the periphery of their light-sensitive area, and only passing on the difference to the brain.

The visual information is thus massively reduced, which is necessary because the retina has about 125 million "pixels", the optic nerve but only about one million "cables". The optic nerve is thus the bottleneck of information transmission.

ON and OFF cells

There are cells in the retina that evaluate whether the center is lighter in the photosensitive area (receptive field) and the surroundings are darker (ON cells). Others judge whether the center is darker and the environment is brighter (OFF cells).

During our normal viewing experience both types are similarly irritated. But how is that when reading text?

Schaeffel has developed a software that quantifies the stimulus intensity for ON and OFF cells in our visual world.

It has been shown that dark text on a light background mainly irritates the OFF cells, while light text on a dark background irritates mainly the ON cells.

Previous experiments with chickens and mice have already shown that ON cell stimulation is more likely to inhibit eye growth, but stimulation of OFF cells may exacerbate it.

Bright text on dark background inhibits myopia

By means of optical coherence tomography (OCT), the thickness of the tissue layers in the living eye can be precisely measured (micrometer range).

Chickens, various monkeys and children have already been researched to find that altering the thickness of the choroid, which is the layer behind the retina, predicts how the eye will grow in the near future.

If the choroid becomes thinner, it indicates the development of myopia, it becomes thicker, eye growth retards, myopia does not develop.

The three researchers have volunteers read dark text on a light background and light text on a dark background.

After only 30 minutes, they were able to measure that the choroid became thinner when reading black text, and thicker when reading text with reverse contrast.

This suggests black text on a light background promotes myopia development, and light text on a dark background inhibits myopia.

Easy to implement measure

Reversing the text contrast would therefore be an easy way to stop the development of myopia, as more and more time is spent working and reading computer screens and tablets.

This strategy against the development of myopia has yet to be verified. The scientists from Tübingen have already planned a study with schoolchildren.

However, your current research shows in the experiment that the choroidal thickness can change in both directions, only by reading with different text contrast. (Ad)