Staring at a computer screen or any other type of screen for long hours makes for less frequent blinking and dry eyes.
Whenever you are focusing on a set task which requires heightened concentration you tend to blink less. This includes working on a computer, looking at your phone screen or tablet, reading or writing. When you blink less your eyes are not getting the chance to replenish their moisture levels.
Additionally, if the distance of your gaze is not varying, say because your computer monitor is always a set distance from you, you can experience eye strain.
When you are working on a screen, make sure every twenty minutes you stare at an object twenty feet away, for twenty seconds. This will give your eyes a chance to ‘reset’ and will help you avoid digital eye strain (also known as computer vision syndrome) as well.