By 3 pm most days my head was pounding and I blamed the work. Then a long weekend away from my desk fixed it completely, which told me the work was not the problem. The screen was.

What happens on a screen is not just light. It is a set of specific habits, and most of them have nothing to do with blue light.

The blink problem

People blink about 15 times a minute normally. On a screen that drops to five or six. Less blinking means drier eyes, and dry eyes cause a large share of what people call screen headaches.

You cannot remind yourself to blink. What works is looking away. Every 20 minutes, look at something 20 feet away for 20 seconds. The away look resets your blink rate without any effort.

Brightness mismatch

A screen brighter than the room around it forces your eyes to work harder. Match the screen to the ambient light instead of the other way around.

At night, that means turning the screen down much further than feels natural at first. Give it 10 minutes and your eyes adjust.

Distance and height

Most people sit too close and too low. The top of the screen should be at or slightly below eye level. Looking down at an angle for hours strains the muscles that focus your eyes.

Arm’s length is the rough guide for a monitor. For a laptop, that means you should probably be using a separate keyboard and raising the screen a few inches.

What did not help me

Blue light glasses did nothing for my headaches. I wore them for three months and noticed zero difference, though they may help with sleep if you use screens late.

What did help: the 20 minute break habit, raising my screen, and a cheap desk lamp behind the monitor to stop the contrast between the screen and the dark wall behind it.

When to see someone

If headaches come with blurred vision, flashing lights, or numbness, that is not eye strain and it needs a doctor, not a new monitor.

For the ordinary afternoon headache, the fix is usually smaller and simpler than people expect.