By the end of the day my eyes burn. The screen goes fuzzy for a second when I look up, focusing on something across the room takes longer than it should, and a dull headache creeps in around the temples. I used to write this off as "just tired." Turns out it has a name and a fairly simple mechanism behind it.
What computer vision syndrome actually is
Computer vision syndrome — digital eye strain, if you prefer the plainer name — isn't a diagnosis in the sense of "something broke." It's a cluster of symptoms that shows up after prolonged close-range screen work: dryness and burning, blurred focus when you shift your gaze to something far away, light sensitivity, headaches, and often neck and shoulder pain, because we unconsciously lean toward the screen and freeze in one position for hours.
Two things happen at once. First, your eyes hold focus on a near object for a long stretch — the ciliary muscle, which controls how the lens changes shape for near vision, stays tensed the whole time instead of periodically relaxing the way it would if your gaze wandered farther away now and then. Second, you blink noticeably less often while concentrating, so the tear film that keeps your eyes moist doesn't get replenished as frequently — hence the dryness.
