Last week, we talked about myopia, or nearsightedness, including the increasing incidence of it around the world. We also talked a little bit about how exposure to outdoor light can help to prevent myopia. Today, we’ll continue the conversation.
Why is preventing myopia important?
Nearsightedness is associated with a variety of complications. Last week I talked about the long-term complications associated with high (severe) myopia. Here are some complications of unrecognized or uncorrected myopia:-
Poor school performance – Delays in reading or other academic skills
-
Difficulty with social interactions
-
Eyestrain
-
Headaches
-
Impaired safety – Not being able to see hazards adequately
What does the research tell us about the link between outdoor play and myopia?
As we discussed last week, myopia is caused by a mix of genetic factors and environmental factors. We can’t change the genetic factors, but we do have some control over the environmental factors.
Researchers from all around the world agree that time spent outdoors reduces the likelihood that a child will become nearsighted. The data supports the idea that the primary reason for this is the bright outdoor light. The strong link between exposure to sunlight and myopia is especially true in families where the parents also had myopia.
How much outdoor time helps to prevent myopia?
-
The current recommendation is for 2 hours per day outside. This is based on multiple research studies done around the world.
-
There are studies showing benefit from less time outside, just not as much benefit. Even adding one additional hour outside in a week can decrease the risk of myopia to some degree.
-
Here’s a rhyme to remember: Go outside and play, two hours a day, to keep myopia away!
-
This outdoor time is also beneficial for teenagers, to lessen the risk of developing myopia and decrease or maybe eliminate the progression of myopia that is already present.
What about the dangers of sun exposure? Didn’t I just tell you a few weeks ago to avoid too much sun exposure due to the associated risks?
There is a fine line we need to walk between healthy sun exposure and damaging our health. I did talk about the dangers of sun exposure in recent Health Tips, including eye damage from UV radiation. So, what should you do so your kids get this benefit from the outdoor light?
-
Go outside (or have the kids go outside) without sunglasses for about 20 minutes a day, preferably in the morning. The rest of the day, particularly between 10am and 2pm, wear good sunglasses with UV protection. Even with sunglasses on, there is benefit. The sunglasses are not blocking all of the bright light.
-
Use sunscreen for outdoor play time. You still get the eye benefits with sunscreen on.
-
You can also have the kids play in the shade on a sunny day, they still get much brighter light in the shade on a clear day than they do indoors.
Can that bright light be recreated indoors?
There are currently some experiments with the idea of glass cube walls to help add light to classrooms. But from the research to date, the amount of light that you need to get the goodness of time outdoors, really has to come from outdoor light.
Light can be measured in different ways, such as lumens, lux, foot candles. Lux is the unit of illuminance, indicating the actual brightness received on the ground. Just for comparison, here are some average illuminance values:
-
A bright sunny day – Around 100,000 lux.
-
Shade illuminated by an entirely clear sky on a bright sunny day – 20,000 lux
-
Indoor classroom light – On average 500 lux
As you can see, there is no real comparison. Outdoor light wins for brightness!
How do you know if your child has myopia?
Make sure they get regular vision screenings, which can be done at their yearly well exam.
-
At least once between ages 3 and 5
-
Before/during kindergarten, usually age 5-6
-
Annually through the end of high school
Also, watch for the symptoms we talked about last week.
If there is a problem on the screening test, or you notice symptoms, they need a complete eye exam with an optometrist or ophthalmologist.
If you have any questions about myopia, please log into your account and send us your question. We are here to help.
Dr. Anita Bennett MD – Health Tip Content Editor