Many of us have a habit of using our smartphone before bedtime. According to doctors, this seemingly harmless habit can cause vision problems as two women in the United Kingdom experienced recurring episodes of short-term blindness after improper use of smartphones in the dark.
According to LiveScience, two women, aged 22 and 40, experienced mysterious vision problems that only occurred at night or early in the morning. 
In the case of the 22-year-old woman, she had experienced several episodes of vision problems in her right eye at night while she was in bed. These episodes occurred several times a week for a year. The patient said that while her vision was fine in her left eye, she was only able to see the outlines of objects with her right eye. The patient’s eye exam turned out to be normal and had no signs of blood clot or other conditions linked to short-term vision loss.
On the other hand, the 40-year-old woman said she couldn’t see out of one eye when she woke up early in the morning, just before sunrise. It occurred for about 15 minutes and happened on and off for six months.
The doctors found out that the vision problems occurred only after the women viewed their smartphone for several minutes using just one eye. They hypothesised that the eye looking at the smartphone becomes adapted to the light, while the other eye is adapted to the dark.
When the smartphone is turned off, the light-adapted eye becomes “blind” until it also adjusts to the dark.
“As they can see well with the dark-adapted eye, it seems to them that they have lost vision in the eye which — a moment ago — was viewing the smartphone normally,” the doctors wrote in the report.
What is the Smartphone’s Effect on Vision and Health?
A report by Business Insider revealed that blue light emitted by electronic devices like smartphones is linked to serious physical and mental health problems.
Exposure to blue light at night time can damage your vision and alter your body’s natural sleep cues. Though more research is needed, blue light has also been linked to cataracts.
Moreover, blue light is believed to suppress the production of the hormone melatonin. When melatonin functions go haywire, your risk for depression and cancer is elevated.