Despite what helicopter parents may have you believe, there’s pretty solid evidence that kids should be encouraged to spend a lot of time outside. Access to greenery boosts health and energy, and gets kids’ brains turning in creative ways that screen time doesn’t.
Now, here’s another reason: Researchers at Northwestern University found that kids who spend too much time indoors may develop myopia. And the potential short-sightedness has nothing to do with them being cooped up and not going outside to look at faraway things, and everything to do with an existence lived under artificial light.
What really determines the eye’s ability to focus is the length of the retina. If it’s long, the person becomes short-sighted; too short, and they become far-sighted. “The eye needs to stop growing at precisely the right time during childhood,” assistant professor of ophthalmology Gregory Schwartz told Northwestern Now. Schwartz is the lead author of a study locating the cell which tells the retina when to stop growing, and it’s that cell that’s affected by how long kids spend indoors versus outside.
This particular cell is highly sensitive to light. To determine focus, it detects contrast, like a camera’s auto-focus. Contrast denotes sharpness, but the actual work of determining if the image is, in fact, in focus is done by a specialized circuit in the brain, which researchers also isolated. One the circuit is happy that the retina can make sharp images, it tells the retina to stop growing.
Artificial light, the researchers found, messes with this process. Because indoor light has a lot of contrast in the red-green area of the spectrum, it can trick the cells into thinking that the eye is focusing when it isn’t. This leads the cells to instruct the retina to keep growing, which results in myopia.
While their existence was expected, the actual cells responsible for this mechanism had not been identified before this study. To do so, the Northwestern researchers used tiny electrodes to monitor the retinal cells of mice while they watched patterns of light. The next step for researchers will be to find the gene responsible for these cells, so they could develop gene therapy for humans to improve eyesight.
The other takeaway from this research is the obvious one: that kids should spend more time outside. And perhaps, this research finally offers a scientific explanation for why nerdy kids always end up needing glasses.