It’s been widely researched that smartphones can make it more difficult for users to fall asleep. The blue light that devices often give off can keep the body from releasing melatonin, the sleep controlling hormone. But they can also cause something called “transient” smartphone vision loss of blindness.

What is transient blindness or vision loss?

Transient vision loss or blindness can happen in one eye or both eyes and it is the loss of vision or partial vision in one or both eyes for a period of time ranging from seconds to hours. It frequently occurs when the blood flow to the eye is restricted, a condition called ischemia, this is a serious disease that can lead to total loss of vision. Other less threatening causes can also cause transient vision loss, these include dry eye or migraines.

Details of two cases of transient vision loss were published in the New England Journal of Medicine in 2016 in which the causes were benign. One case involved a young woman in her 20s who experienced vision impairment at night in only one eye. The second patient was 40 years old and experienced issues with her eyesight upon waking up over a period of six months. Both women were in good health aside from their vision problems.

The researchers looking into the cases hypothesized that the two women were experiencing eyesight issues because they were putting their eyes through photopigment bleaching, during which one eye was forced to adapt to bright light and the other was not. The bleached eye then had to undergo recovery, during which time the sight came back. This happened when they used their phone or another device with a screen and only one eye was fully exposed to the harmful light 

A study from the Universidad Complutense de Madrid found that the LED lights in screens could lead to eventual blindness. This occurs because the lights can cause damage to the retina that cannot be undone.