They say using your smartphone in bed is bad, but this is really bad.

Medical professionals are warning phone users about “eye strokes” after a man in China went temporarily blind after staring at his device in the dark, reports the South China Morning Post.

The man, identified as Wang, from Xi’an in Shaanxi province, says that he momentarily lost his sight after playing games on his smartphone with the lights off.

“I was using my right eye to look at my phone, and I could see some words but not others,” said Wang of the frightening incident.

Doctors there diagnosed him with a central retinal artery occlusion — known as an “eye stroke” — a condition caused by a blockage of the arteries carrying oxygen to the retina. The ocular clot can result in severe vision loss if not treated immediately, as was allegedly the case with Wang. The report didn’t specify whether he went blind in one or both eyes.

Wang’s doctor, Lei Tao, attributed Wang’s blind spell to an “overuse of electronic items,” which can lead to “excessive strain on vision.” Wang indeed claims he had a habit of playing on his phone after going to bed — much to the annoyance of his wife.

Temporary screen-induced sight loss is a growing epidemic among smartphone users, according to Lei, who says he sees around 20 (mostly) young sufferers of the ailment every month. Lei adds that “the rate of [permanent] blindness is also high.”

However, US eye experts are taking the report with a grain of salt.

“To make the claim of an eye stroke, there should be documentation,” Dr. Gareth Lema, a retinal surgeon at Mount Sinai’s New York Eye and Ear Infirmary, tells The Post.

Lema says that retinal artery occlusion only occurs in about 1% of the general population and usually affects older people suffering from “carotid artery plaque or cardiac valve disease.” Read more at NY Post