Sun protects against myopia

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MunichThe number of myopic people is increasing steadily. The good news is: In many cases, ametropia can apparently be prevented with one simple measure: spending more time outdoors. That is at least true in youth.

That bookworms and academics are more likely to have bad eyesight is not just a myth. Studies show that the proportion of myopic people increases with each year of training. The so-called close work such as reading and writing strains the eye in the long run. Because the lens has to be adjusted by tiny muscles so that the near area is sharply focused on the retina. Researchers at the University of Tübingen suspect that this stimulates the eyeball to grow in length over the long term - so the close-up image is sharp even without great effort. The big disadvantage: objects in the distance can no longer be shown in focus.

Lack of light

This process is evidently favored by another circumstance: those who learn a lot spend a lot of time in classrooms, lecture halls or libraries. Accordingly, the couch potatoes spend little time outside in bright daylight. The lack of light also apparently promotes the elongation of the eyeball and thus myopia. "Spending time outdoors counteracts myopia in children - presumably because of the better light conditions," explains Prof. Frank Schaeffel from the Research Institute for Ophthalmology at the University Hospital in Tübingen.

Dopamine - messenger substance for the eye

The messenger substance dopamine plays a decisive role in this. Its distribution in the eye follows a daily rhythm. It increases in the morning and then decreases again in the evening. The messenger substance regulates which of the specialized sensory cells in the eye are activated - the rods or the suppositories. Suppositories allow you to see in color, but they are not particularly sensitive to light. They are therefore used especially during the day. Rods, on the other hand, get by with little light, for example at night, but do not allow color vision.

Dopamine may have even more effects: it apparently slows down the elongation of the eyeball and thus prevents nearsightedness, suspect Regan Aschby and his colleagues from the University of Tübingen. And since dopamine is mainly released when bright daylight falls in the eye, regular outdoor activities could prevent myopia. The scientists had already established this connection earlier in the course of various animal experiments. This could apply to humans, at least in their youth, when the eyes are still changing constantly.

Three hours in the open air

Children would have to expose themselves to a light intensity of 10,000 lux for around three hours a day to prevent myopia, estimates eye expert prof. Ian Morgen from the Australian National University. This is only possible outdoors: even in well-lit interiors, only around 500 lux are achieved. The conclusion of the experts: "Children should play outdoors as much as possible."

Short-sighted people see close objects clearly, while distant objects are out of focus. Around every third German is currently affected - and the trend is rising. Glasses and contact lenses correct the ametropia, but they do not correct the cause. Laser treatment can help in the long term, but it is associated with risks. Independence from the glasses is also no guarantee.

Sources:

Press release of the German Society for Endocrinology from April 29th, 2015

Schatz H .: DGE blog post from 10. April 2015

Dolgin E .: The myopia boom. Nature 519, March 19, 2015, doi: 10.1038 / 519276a

Ashby, R. et al .: The effect of bright light on lens compensation in chicks. Investigative Ophthalmology & Visual Science. doi: 10.1167 / iovs.09-4689

Ashby, R. et al .: The effect of ambient illuminance on the development of deprivation myopia in chicks. Investigative Ophthalmology & Visual Science. doi: 10.1167 / iovs.09-3419.

Mirshahi A. et al .: Myopia and level of education: results from the Gutenberg Health Study. Ophthalmology. doi: 10.1016 / j.ophtha.2014.04.017.

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