Comment by mattjaynes

I've read this study a while ago, and I think it helped me correct my son's myopia.

When my 5yo kid's eye check came back with "he'll need glasses next year", we started strict "hour+ outside play daily" policy. At his next checkup, he had normal vision. Dr was surprised.

People who have the hobby of photography, might have some intuitive understanding of this brightness difference. If you are shooting with fixed aperture and ISO, your exposure times could easily go from 1/60 indoors to 1/3000 outdoors which is not quite a 100X difference, but close.

Light perception is logarithmic, not linear, which is why your guess is so far off.

7 'shades' brighter and you're already hitting '100x'.

> I bring this up because one of the largest factors in myopia development appears to be outdoor light exposure in childhood.

I used to live almost on the equator. Before adolescence, I would spent most of my time outdoors. Very stable weather so windows were open most of the day (and night). There was often direct sunlight even indoors. We would go to the beach every weekend. I ended up with -5.00 and -5.25

Maybe this would decrease the prevalence, if you are looking at the entire population. But it's not like you, as an individual, will be immune if you just stay outside.

That's only correlation, light brightness has nothing to do with myopia. It's more likely from looking at things farther away from the face outside so that there is less light focused on the fovea.

When I tried to inject fake daylight into my basement office, I realised just how "special" daylight is. It comes in from everywhere. Flood fills with so much light as such a broad spectrum.

I always thought my myopia was caused by computer usage. Reading this it sounds more likely that it was growing up in Calgary, Canada and spending huge amounts of time indoors and in basements.

I made an appointment with a local dermatologist about some sunburn that never seems to heal up. He's a young German guy living here in New Zealand. After a quick examination: "So! You have solar keratosis! How long have you been wearing the hat?" Me: "Oh 5 years or so". Him: "And how long have you lived here?" Me: "All my life, 60 years". Him: "Just so! It seems all Kiwis have solar keratosis ja?".

In other words, there are downsides to being outside in that 1000 times (maybe 10000 times here) brightness. The really annoying thing is that my eyes were buggered from a young age too, despite all that brightness.

> Genetics are likely a factor too, but light exposure seems to have a huge effect: "The prevalence of myopia in 6- and 7-year-old children of Chinese ethnicity was significantly lower in Sydney (3.3%) than in Singapore (29.1%), while patterns of daily outdoor light exposure showed that children living in Singapore were exposed to significantly less daily outdoor light than Australian children."

So, it's not even an individual correlation but a population-frequency-correlation between populations in different physical environments, which is so even more likely than an individual correlation to represent an effect other than causation in either direction, such as any other environmental (or population-genetic-distribution) difference.

Just as a side note, its not that people are terrible at perceiving brightness, it's just that brightness perception (like loudness) is logarithmic. So if a person says it is 2x brighter outside, and a linear measurement instrument says it is 100x brighter, that is in fact roughly consistent.

I’d wager there’s an effect like this for adults too. I didn’t need glasses until I got my first office job.

> (For specific numbers and comparisons, see: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6656201/ )

The study was done in Singapore and Malaysia. It looks like an interesting study to do in different regions of the world. e.g Western Europe where it is notably cloudier than Singapore.

I noticed that when I started to measure the lightning in a room for home automation purposes.

It is really, really difficult to find the right spot that reflects "the light in the room" and then to find a threshold to switch on the lights "at the moment I would have done that".

I constantly hesitate between 30 and 100 lx, it is so dependent on the subjective light outside.

I remember reading a post on here about someone's home office lighting setup which had some insane number of lumens and was equivalent to being outdoors at dusk. That's when I became aware of the huge difference in illumination.

Before you change your internal mental calibration, this of course changes based on latitude and time. The difference between daylight and a cloudy day midwinter in Northern Europe is probably not going to be 100x.