- What can we say about the environmental conditions in which kids are seen from the time they're born through let's say adolescence and their teen years in terms of how their visual system wires up? And are there any recommendations that are coming from the scientific literature, clinical studies, clinical trials, excuse me, or otherwise that indicate what a healthy visual environment consists of?

- Yeah, yeah. That's a great question. And actually it's really relevant these days because myopia is so common. It's more common in Asian populations. It's called an epidemic in China. In California, we have a lot of Asian heritage or Asian Americans. And so we see a lot, like at Stanford, we see a lot of myopia in kids and adults and really starting to get thoughtful on the science of myopia control.

How do we provide the right environments? Now, what's interesting is that for decades, the assumption, some of the data really led us to the path of thinking like, gosh, the more you spend at near activities, and these are mouse model experiments like you described, but also well-designed human cohort studies, figuring out like asking kids and families, like how long is your kid reading or in front of the computer?

How myopic are they? How nearsighted are they? Versus how much time is your kid in front of the computer doing near work? How myopic or nearsighted are they? And these well-designed cohort studies did point towards this concept that if you do too much near work as a kid, that you're more likely to develop nearsightedness as you get through those sort of preteen and even into the teen years, which is when most of that myopia progression or eyeball elongation is actually happening to cause nearsightedness.

It's only been in the last few years that some really exciting studies have actually pointed in a slightly different direction. And that's that maybe it's not all, not to say it's not about near activity, but maybe it's not all about near activity. Maybe it's actually a little more about the kind of light we're getting into our eyes.

And I think you've talked about this before, and it's really important. When they've now studied and asked the kids, instead of just how much near and how much far are you doing, how much time are you spending indoors in indoor lighting, which doesn't have full spectrum light in a typical indoor environment, versus how much time are you spending outdoors, playing in the yard?

You could be reading outside, but what kind of time are you spending outside? And of course, when you're outside in sunlight, even it's in direct sunlight, you're getting a different spectrum of kind of full spectrum lighting from the sun. And it looks like it's pretty clear now, actually, that it has maybe more to do with outdoor lighting time than just near work.

And so I think that we've actually already seen the first couple of randomized controlled trials where they're having kids intentionally spending time outdoors versus sort of standard life, which is gonna be often much more indoor time. And seeing some effects, you follow those kids over a couple of years, and the kids who spend time outdoors are progressing in their nearsightedness less.

Like their nearsighted prescription is not getting as strong as the kids who are spending more time indoors. And there's some pretty good biology that's getting worked out, going back to animal models, more about how that might be working in the retina, in this inside the eye. But it's pretty compelling concept.

And so, as a parent, you may wanna be telling your kid, like, okay, yeah, I want you to read that book, or if your kid's playing on the phone or something like that or the iPad or something like that, they're allowed that time. Okay, you can have that time, but I want you to spend some of the time that you're doing that outdoors.

- Are there any thresholds for the amount of time that one would suggest their child be outdoors to get that full spectrum light? - It's a great question. We talk about cohort studies where we just ask people, what are they doing? And there seems to be a little bit of what we would call a dose-dependent response.

Maybe the more time outdoors might be better. We don't know if there's an upper limit. Like, gosh, if you go over two or three hours, there's no additional benefit. We talk about that in cohort studies. The real gold standard for answering these kinds of questions are randomized controlled trials and specifically placebo-controlled or a control group that's not getting the intervention.

That's our highest level of evidence for clinical evidence for any of this kind of science when we're talking about humans or preclinical models in the laboratory. And the study that hasn't been done yet to really answer that question is to randomize kids to telling this group of kids, you just do your normal life.

Tell this group of kids, we want you outside an hour. This group of kids, we want you outside two hours a day. This group of kids, three hours a day. And see between the groups, is there a big difference? Like, we have pretty good evidence now from the studies that have been done that the difference between zero and one or two hours is clearly there.

Is five minutes enough? Is five hours better? I don't think we know the answers to those questions yet. Like, what's the right dose? But there's probably at least some dose dependence to that. - And I can imagine it's a little bit hard to tease apart the near far viewing from the indoor outdoor because yes, of course, a child could be outside on an iPad up close, but it's hard to imagine that at some point they aren't seeing off into the distance, far viewing as it's called.

And the reverse is also true if you're indoors, unless you live in a very, very large home or you're staring off a balcony, far viewing is much harder to achieve. And perhaps it isn't important to isolate these variables. Although I can see the challenge in developing a really good clinical trial, randomized clinical trial for this.

Meanwhile, I'll go into the grave shouting, or saying rather and suggesting that people get some morning sunlight in their eyes to set their circadian rhythm. But far viewing a few, at least a few minutes and ideally hours per day, or a mixture of near and far viewing by being outdoors just seems like a good thing to do regardless of age.

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