Best/Worst Habits for Eyesight: 20-20-20 Rule & more

Nine common beliefs people have about eye health, and what experts have to say about them.

1.  Reading a book or looking at an electronic device up close is bad for your eyes.

True. Our eyes are not meant to focus on objects close to our face for long periods of time, said Dr. Xiaoying Zhu, an associate clinical professor of optometry and the lead myopia researcher at SUNY College of Optometry in New York City. When we do, especially as children, it encourages the eyeball to lengthen, which over time can cause nearsightedness, or myopia.

To help reduce the strain on your eyes, Dr. Zhu recommends following the 20-20-20 rule: After every 20 minutes of close reading, look at something at least 20 feet away for at least 20 seconds.

2.  Reading in the dark can worsen your eyesight.

False. However, if the lighting is so dim that you need to hold your book or tablet close to your face, that can increase the risks mentioned above and create eyestrain, which can cause soreness around the eyes and temples, headache and difficulty concentrating. But these are usually temporary symptoms, Dr. Zhu said.

3.  Spending more time outside helps eyesight.

True. Some research (mostly focused on children) suggests that outdoor time can reduce the risk of developing myopia, said Maria Liu, an associate professor of clinical optometry at the University of California, Berkeley. Experts don’t fully understand why this is, but some research suggests that bright sunlight may encourage the retina to produce dopamine, which discourages eye lengthening, though these experiments have mostly been conducted with animals, Dr. Zhu said.

4.  Too much ultraviolet light can harm eyesight.

True. There is a reason experts say not to stare at the sun. Too much exposure to ultraviolet A and B rays in sunlight can “cause irreversible damage” to the retina, Dr. Ehrlich said. This can also increase your risk of developing cataracts, he said.