We are not born with perfect vision

How our vision develops during childhood

Interview with Dr. Arne Ohlendorf, Optometrist and Visual Scientist at the ZEISS Vision Science Lab in Tübingen (Germany)

 

We certainly don’t come into the world with perfect eyes. So how well can a baby actually see?


It takes a while for our eyes – and in particular our perception of the world – to fully develop. Babies are born with plenty of visual impairments. The cornea and the eye’s lens, and to a certain extent the length of the eye itself, have a defined refractive power. During childhood, the body balances itself out; the same is true of its refractive power, which is related to the eye’s elongation and allows us to see objects clearly at a distance. For example, if the eye is too long a person will be short-sighted as the clear image of the surrounding is formed in front of the retina.

Certain other aspects of visual performance, such as color and contrast vision, are still being developed and are not a given from the get-go. For instance, our visual acuity increases every month, and by the age of three it is well-developed and comparable to that of an adult. So the fact that babies respond well to their parents isn’t actually down to them seeing clearly. It’s much more about them recognizing their voice and behavior.

Can babies see in color?

The biological basis for color recognition, i.e. the relevant sensors, are found in the eyes – and they’re already working away. However, we must first learn to recognize blue, red, yellow and all the other colors. Put simply, a baby doesn’t yet understand what it sees. Only a part of the development of our visual perception is related to the eyes working as sensors. The brain plays a key role here by processing visual information.

When do the eyes become fully developed and operational?

We refer to a process called emmetropization. It describes the point in time when normal vision develops, which occurs between the ages of 6 and 8. Emmetropization is where all the refracting parts of the eye, or the dioptric apparatus, are perfectly matched. An emmetropic eye requires no visual aid. It needs no assistance when looking into the distance in order to generate a sharp image on the retina. If someone has a visual impairment, emmetropization will not occur and they will need glasses to correct it.

Nevertheless, the eyes will always continue developing, changing, and aging. Following emmetropization, by the age of 20 or 25 we should not expect any typical, visible impairments in addition to the existing visual impairment.

So why does one get the feeling that there’s an increasing number of short-sighted young people these days?

It’s not just a feeling. In Asia especially, the number of cases of progressive myopia (short-sightedness) has risen to epidemic proportions. Today, 90 percent of under 20s living in several Asian cities are short-sighted. Studies show that, by 2050, almost 50 percent of the world’s population could be short-sighted. Visual impairments that can be rectified with a pair of glasses could one day lead to health problems if a person’s short-sightedness progresses too quickly or if their prescription becomes very high. These are problems that can no longer be corrected with a visual aid but which may concern, for instance, the retina itself.

Why are so many young people today short-sighted?

There is no definitive answer to that question. What we do know is that near-vision activities such as reading are linked to short-sightedness. Of course, genetics also has something to do with this. In any case, it’s important to understand that “school myopia” is not a recent phenomenon. In the past, schoolchildren who read a lot were likely to become short-sighted; this predated the advent of tablets, smartphones and other devices. Today, the high number of cases of short-sightedness is also impacted by other factors.

How can we counteract this?

Distance vision is good for the eyes, whether a person has normal vision or an impairment. The general recommendation is to look at an object 20 meters away for 20 seconds, and repeat this every 20 minutes. This is known as the 20-20-20 rule. Short-sighted people have become accustomed to looking at objects a short distance away as a result of their near-vision activities. These people see clearly in the near vision distance but have trouble making out faraway objects. Alongside distance vision, a study in Taiwan has found that natural light is a particularly important factor. Being exposed to just two hours of daylight each day can do a lot to slow the progression of myopia. For children in particular, this means putting away their smartphones and getting some fresh air. All in all, some things are very beneficial for our eyes: daylight, a balanced lifestyle, fresh air and gazing into the distance from time to time.

 

Thank you very much for talking to us.

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