Surveys show that more than 80 percent of people use their phones before going to sleep. Even when they feel sleepy, most still continue scrolling.
Your mind may tolerate it, but your eyes often cannot. Mental fatigue can recover quickly, but eye fatigue is harder to reverse. Using a phone while lying down can place significant strain on the eyes in three main ways.
Too close to the screen
When people lie in bed at night, they often curl up under the covers and hold the phone directly in front of their face. That position places the screen much closer to the eyes than during normal daytime use.
When sitting upright during the day, the distance between the eyes and the phone is usually about 30 to 40 centimeters (12 to 16 inches). But when lying down—especially when nearsighted people remove their glasses—the distance may shrink to around 20 centimeters (8 inches) or even less.
The closer the screen is, the harder the eyes must work to focus. Over time, that extra effort increases eye strain and fatigue.
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What people usually notice is that their eyes feel tired. What they may not notice is that subtle vision problems can develop gradually, such as slower focusing or blurred vision when looking at nearby objects.
Using the phone in the dark
Pupil size changes according to light levels. In bright conditions, pupils become smaller. In darker environments, they expand to allow more light into the eyes.
When someone lies in bed using a phone in a dark room, the surroundings are dim, which causes the pupils to dilate. At the same time, the bright phone screen pushes them to contract. As a result, the eyes must constantly adjust to the competing light conditions.
This repeated adjustment can strain the eyes.
Using a phone in very low light may also cause subtle internal changes within the eye that could affect fluid balance and potentially increase eye pressure.
For people with severe farsightedness, structural eye abnormalities, or a family history of glaucoma, such conditions may trigger acute glaucoma, a disease that can lead to vision loss.
Staring at the screen for too long
Every time we blink, tears spread across the cornea and keep the surface of the eye moist and healthy. However, the tear film only lasts for a limited time before it begins to break up.
Under normal conditions, people blink about 10 to 20 times per minute to maintain eye moisture.
When focusing intensely on phone content, people tend to blink less often. Without sufficient blinking, the tear film cannot protect the eye surface properly. The result may be irritation, dryness, and discomfort.
Over time, this can disrupt normal tear production and reduce tear film stability, leading to dry eye and worsening eye fatigue.
How to reduce eye strain when using your phone at night
If giving up the habit of using a phone before sleep feels difficult, several simple adjustments may help reduce eye strain.
Turn on a bedside lamp
Using a phone in complete darkness puts more strain on the eyes. Instead of turning on a bright overhead light, try using a small bedside lamp so the phone screen is not the only light source in the room.
Lower the brightness of the phone screen or switch to night mode to reduce glare.
Sit up when using the phone
If lying down brings the screen too close to your eyes, try sitting up and holding the phone in a posture similar to daytime use. Maintaining a healthier viewing distance can reduce eye strain.
If you mainly watch videos, using a phone holder beside the bed may help keep the screen farther away.
A larger screen device, such as a tablet, can also make it easier to view content from a comfortable distance.
Blink more often
To prevent dry eyes, remind yourself to blink frequently.
If dryness persists, check whether indoor air is too dry. A humidifier may help improve moisture levels in the room.
Follow the 20-20 rule
Remember the 20-20 rule: after looking at a screen for 20 minutes, rest your eyes for 20 seconds. Although commonly recommended for daytime screen use, it can also help protect your eyes at night.
