The environmental causes of myopia - a case study

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In modern times, myopia is taken for granted. A lot of people need glasses, contact lenses or a scary operation, and that's the way it is. 

Still, myopia doesn't seem to be a genetically determined necessity for most of those people. Scientific consensus says that time spent outdoors during childhood is negatively associated with myopia. Near work like reading or sewing is associated with myopia. Living in a city and having high socio-economic status is associated with myopia too. All this is well summarized by Wikipedia’s myopia article. 

The apparent environmental effects are very large. In rural Nepal, one study found that only 1.2 percent of children aged 5-15 were myopic. In Singapore, scholars claim that 83 percent of young adults are myopic. Myopia rates seem to have increased over time. In one study the prevalence of myopia in American schoolchildren aged 12–17 years increased from 12% in the early 1970's to 31% in the early 2000's.

What is going on? Researchers can see that it is something with being outdoors. People who spend more time outdoors are less myopic. But researchers don't know why. Is it because sunlight is good for the eyes, or is it because looking far away is good for the eyes, or is it both? 

A domestic experiment

My bet is on the latter: Myopia is caused by not looking far away often enough. The reason why I think so is highly personal. 

In the winter of 2020/2021 schools for over 12-13s were closed and replaced by distance teaching in the area where we live. My oldest kids, then aged 12 and 14, mostly stayed in their rooms. But the 14 year old, who is a very disciplined and slightly autistic person, also took a lot of pauses and went outside. There he always walked in circles, looking at his own feet. Since we have told him that being outdoors is good for his health, he took such pauses several times a day, despite the lackluster weather with dim Scandinavian winter light and temperatures around the freezing point.

Nominally, my son got his outdoor hours, but it wasn't like in normal times. For example, he never rode his bike. When school is open, he  always bikes 12 kilometers to school, both ways, five days a week. During lockdown his outdoor time consisted of walking and looking at his feet.

In the spring school started again and so did school health check-ups. A school-nurse called me and said my son needed to go to the optician because he had myopia  on one of his eyes. The optician confirmed his vision was significantly impaired on one of his eyes . But his other eye was fine, the optician said, so he didn't need glasses now if he didn't have headaches from his uneven vision. We should just wait for the other eye to deteriorate too (it probably would, the optician said) and then come back and buy him a pair of glasses. 

Anders and I were not in the mood to wait and see. We instantly suspected that our son's rapidly deteriorated vision was due to his weird behavior in the winter. We told him that he had probably caused his loss of vision himself by not looking at his surroundings when he was outdoors. He confirmed that he seldom looked far away, saying that the view didn't interest him. He never looked out of the window, he said. I insisted he should start pretending that the trees and the fields interested him.

He did. Being a very disciplined person, he started to look up and out of the window once a minute. He spends a lot of time outdoors, also when he reads, and he often looks up from his book. We bought an optician's table and gave it a prominent position on a wall in the house in order to follow his progress (or deterioration). After only a couple of months he had almost the same vision on both eyes again. He was no longer myopic. 

Could this be science? 

A meta-study says that increasing outdoor time once myopia has started doesn't halt its progression. But the meta-study only analyzed outdoor time. It didn't ask where the study participants looked when they were outdoors. My son also spent a lot of time outdoors when he became myopic, in fact he probably spent more time outdoors during lockdown when he was not forced to spend a good chunk of the day inside a school building. He just didn't use his outdoor time to look far away. Could that also be the case with other myopics? The more myopic you get, the less fun it should be to look far away. 

It should be rather easy to run an intervention study over this: Select two schools in two different parts of any industrialized country. In one school, teenagers who are developing myopia would be told to look far away more often and to look up from their screens once in a while. The other school could just silently identify teenagers who are developing myopia as a control group. Then the two groups could be compared. Why not? It would even be a rather cheap study. I am a bit surprised that I can't find such a study. The closest I can find is this study that randomized schools in Taiwan to up to 11 hours of outdoor recess every week. In contrast to in the earlier mentioned meta-study, the randomized study found that also children who were already myopic benefitted from more outdoor time. 

I see other reasons than my own son that there is something into the looking far away hypothesis. 

• If it was only about sunlight, latitude would matter at least a little. Scandinavians would be more myopic than Italians, and so on. Instead, the most myopic places in the world seem to be sunny Singapore and Hong Kong. Only 13 percent of 16-19 year olds in northern Norway were considered myopic in one study. That doesn’t indicate that lack of sunlight is to blame. 

• Animal studies show that both light deprivation and the wearing of distortive contact lenses leads to myopia. 

I have also started to question what is in the heritability of myopia. Is the heritability mostly in the eye tissue or is it in the behavior? Could it be both? Anders and I are not myopic, but we have several close relatives who are: Two parents, two out of three siblings. Those parents and siblings have lower levels of general curiosity about the world than we have. Did we save ourselves from myopia through being curious about our surroundings during our teens? I can't find any study that mentions the hypothesis that myopia protection genes are looking-at-one's-surroundings genes to one or another degree. 

If many cases of myopia could be prevented by looking far away, the upside would be huge. People have their reasons to be indoors. But do they have any important reasons for not looking out of the window? If looking up helps against myopia and if people knew that, it could be one of the most cost-efficient public health interventions ever.