Blinded by Smartphone: How Using Your Phone the Wrong Way Can Temporarily Cost Your Sight

You don't need a doctor or an online health expert to tell you that you should unplug from your electronic devices when you go to bed.

Constant access to social media, instant messaging, email, and website updates gives the digitally overconnected a kind of technological hangover. Several years ago researchers at Michigan State University published the not-especially-surprising conclusions of a study that found that people who were on their phones for work after 9 p.m. were less productive and more fatigued than their unplugged counterparts. Smartphones are "almost perfectly designed to disrupt sleep," one of the authors of the study, Dr. Russell Johnson, told the press. Because smartphones keep us mentally connected to work until late in the evening, they make it harder to fall asleep and stay asleep.

Even worse, light emitted by cell phones prevents the pineal gland of the brain from making the hormone melatonin to help you get to sleep. Visible blue light in the frequencies between about 420 and 500 nanometers stops the production of the sleep hormone. Before there were cell phones, computers, televisions, and night lights, this ability to detect the first hints of morning light kept people from oversleeping in the morning. When the eyes are constantly bathed in blue light, however, it keeps people from getting to sleep in the evening.

Just how detrimental is the presence of blue light? Our eyes are so sensitive to blue light that it registers on our retinas even when our eyes are shut. Having a light on won't completely prevent sleep for most people, but it takes, on average 10 minutes to fall asleep in an environment in which blue light is detectable. Once people get to sleep, having a light on in the room can deprive them up to 50 minutes of rapid eye-movement (REM) or dream sleep, leaving them notably groggier the next morning.

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But it isn't just feeling groggy that's the problem. When the same people get up, their vision is fuzzier. The reason for this is a phenomenon known as over-accommodation. In the very middle of the retina there is a small indentation called the fovea. This part of the retina has unusually sharp vision. However, it doesn't have a lot of the cones that detect blue light. The retina is more sensitive to blue light in a ring around the fovea known as the parafovea. 

When you operate a smartphone in the dark, you basically have a tiny blue light emitter in bed with you. The blue light from the phone stimulates the parafovea, where you have fuzzier vision, but not the fovea, where you have sharper vision. As a result, when you get up the next morning in normal light you have a fuzzy view of the world around you. You can't see distant objects as well as you normally can. If you are middle aged or older, you may not see anything at all clearly for a while after you get up. In extreme cases, there can even be blindness.

How To Avoid Going Blind From Using Your Smartphone

The two women in the UK who went temporarily blind from using their smartphones went to their doctors after having repeated episodes in which sight in one eye went away, came back, and went away again. This condition, known as transient monocular vision loss, is the kind of symptom that raises an alarm with emergency room and family care physicians. Often loss of vision is caused by a blood clot temporarily stopping circulation in the eye or in the brain. For the symptoms to come and go suggested that either there was some underlying problem that was generating lots of blood clots, or that a single blood clot was lodged in a precarious position from which it might become "stuck" and cause permanent damage.

One of the women was 22 years old. She had a habit of lying on her left side, her head buried into the pillow, and checking her smartphone before she went to sleep at night. She was blind in her right eye when she had to get up and turn on the lights at night. Her primary care physicians had ordered vitamin A testing, which came back normal, MRI angiography to check the blood vessels in her eye, which came back normal, and tests for blood clotting disorders, which also came back normal.

The other of the women was 40 years old. She had a habit of lying on her side in bed and checking her smartphone before she got up in the morning. She was blind in one eye when she got out of bed and turned the lights on to get dressed. Her doctors had put her on Aspirin therapy.

Both women had a habit of looking at their smartphones in bed while lying on their side. They had one eye open and one eye closed, beneath the pillow. The eye that went temporarily blind was always the eye that they had used to look at the smart phone, never the eye that was closed beneath the pillow. 

There wasn't really anything wrong with their eyes, the ophthalmologists concluded. The problem had been a common, reversible "bleaching" of a pigment called rhodopsin, which the eyes use to register blue light, in the open eye while the women looked at their phones.

READ Modern Technology And Digital Eyestrain

You've probably had a similar experience. In the dark, it's easy to see a dim, blue light. Your eyes adjust to seeing in this intensity of light. If you suddenly go outside into bright sunlight, you will be blind for a few minutes while your eyes generate all the other pigments they need to see the full range of colors in intense illumination.

So how can you avoid this problem?

• If you are using your smartphone in the dark, look at it with both eyes, not just one.
• If fuzzy vision is a problem, avoid using the background illumination feature available on nearly all smartphones. Don't increase background illumination for easier reading.

Let your eyes do the work of reading in the dark, not the screen. Or even better, turn off your phone and get some sleep. Let messages wait for the morning, after you have had a chance to wash and get dressed.