It kind of sounds like one of those things your parents would say to you as a kid to get you to stop misbehaving. 

"Don't look at your smartphone at night it's bad for you!"

Well apparently it can actually be bad for you. Doctors are reporting that two different women suffered from temporary blindness after they checked their phones in the dark too much. 

It could have been easily avoided though. All the women had to do is use both eyes to look at their phones instead of just the one.

In the New England Journal of Medicine, doctors detailed the cases of the two women, aged 22 and 40, who experienced “transient smartphone blindness” for months. The women were subjected to a variety of tests including MRI scans and heart tests but the doctors couldn't find anything wrong with them to explain the problem. 

However an eye specialist was able to detect the issue within minutes. He discovered that both women typically looked at their smartphones with only one eye while resting on their side in bed in the dark. Their other eye was covered by the pillow.

“So you have one eye adapted to the light because it's looking at the phone and the other eye is adapted to the dark,” said Doctor Plant from Moorfield's Eye Hospital in London. "When they put their phone down, they couldn't see with the phone eye. That's because “it's taking many minutes to catch up to the other eye that's adapted to the dark,”

He said the temporary blindness was ultimately harmless, and easily avoidable, if people stuck to looking at their smartphones with both eyes.

Other researchers on the effects of smartphones have doubted whether many other people would experience the same problem citing that two cases weren't enough to prove that one eyed smartphone use in the dark caused the women's problem. 

Via Independent UK