How to reduce eye strain at a computer

Almost everything written about tired eyes at a desk turns into a shopping list within a paragraph — a lamp, a light bar, a pair of computer glasses. This page does the opposite. The fixes below cost nothing, come straight from occupational-safety sources, and are about your behavior and where your screen sits rather than about what you buy or how bright the room is.

We keep the light-level question on a separate page on purpose, because it is genuinely contested and does not belong tangled up with the free fixes. Two national safety bodies publish desk-lighting numbers that differ by a factor of about 2.6, and we walk through why on lighting for eye strain. Here we are deliberately leaving lux alone. This is about focus distance, blink rate, screen distance and screen height — the levers you can move this afternoon without spending anything.

None of it is medical advice, and we say more about that at the end. Stephen reads standards documents, not eye charts.

The 20-20-20 rule, word for word

The single most-quoted piece of advice on this topic is also one of the few that comes verbatim from a national body. The Canadian Center for Occupational Health and Safety puts it like this:

“At least every 20 minutes, take a 20-second break and look at something 6 meters (20 feet) away.”

Notice what that rule is notabout. It says nothing about brightness, colour, or lux. It is entirely about focus distance. The muscles that focus your eyes — the ciliary muscles that bend the lens — hold a single near position for as long as you stare at a panel roughly half a meter from your face. Holding any muscle in one position for hours is tiring, and the eye is no exception. Looking at something 20 feet away lets that focusing effort drop to almost nothing for 20 seconds, which is the entire mechanism.

This is why the rule works from any chair, in any room, under any lamp. It is not correcting your lighting; it is interrupting a sustained muscular hold. It is also why no product replaces it — a light bar changes the room, not how long your focus sits locked at one distance. If a full 20-minute cadence is more discipline than a real workday allows, the direction still holds: the longer you go without lifting your eyes off the panel, the more of that hold accumulates.

Blink, and take the break you keep skipping

The look-away in 20-20-20 does a second quiet job worth naming. People blink markedly less when they concentrate on a screen than when they talk or read on paper — attention suppresses the reflex. A blink resurfaces the tear film across the front of the eye, so blinking less leaves that surface drier and grittier by the end of an afternoon. We are describing a mechanism here, not handing you a number: we have not counted anyone’s blinks and are not going to pretend a figure we did not measure.

The practical version is unglamorous. The scheduled look-away is also a scheduled blink and a scheduled change of posture. Standing up to refill a glass of water pulls your eyes off the panel, resets your focus distance, and gets you to blink normally for a minute — three of this page’s fixes in one trip, and it does more for tired eyes than most of what gets sold for them. The habit is the intervention. The hardware is optional and, on this page, absent.

How far the screen sits from your eyes

Two things about the screen’s position matter, and both are geometry rather than brightness. The first is distance. OSHA’s computer-workstations eTool gives a plain range: the “preferred viewing distance is between 20 and 40 inches” from your eyes to the screen.

A screen pulled in close — a laptop flat on the desk, a monitor shoved to the front edge — forces your eyes to converge and focus harder, which is exactly the sustained near-work the 20-20-20 rule is trying to relieve. Sliding the monitor back to about arm’s length is free, and for a lot of people it is the single change that takes the edge off. There is a common objection here worth answering directly: if the text gets too small at 20–40″, the fix is the operating system’s display scaling, not dragging the panel back toward your nose. Bigger text at a comfortable distance beats small text held close.

If you run two screens, distance and angle start to interact — a second panel off to the side changes how far and how often your eyes have to travel, and a screen you keep turning your whole head toward is a different problem again. We work that through on dual monitor ergonomics, because the single-screen distance rule does not simply double.

How high the screen sits

The second geometry lever is height, and it does double duty: it affects the eyes and the neck at once. OSHA’s figures are specific. The “top of the monitor should be at or slightly below eye level”, and the “center of the computer monitor should normally be located 15 to 20 degrees below horizontal eye level.”

A screen set too high — a monitor on a tall stand, a laptop propped on a stack of books, an all-in-one at a fixed height — pulls your gaze up and, over an afternoon, tips your head back with it. That opens the eyelids wider, exposes more of the eye’s surface to the air, and asks the neck to hold a position OSHA’s good-working-positions guidance is explicitly against: it wants the head balanced over the spine, not craned back or forward. A screen set too low tips the head forward instead, which trades the wide-open-eye problem for a bent-neck one. The published band is the compromise that keeps both reasonable.

Getting there is a measuring job, not a buying one, for most people: the exact height, and how to reach it with what you already own, is the whole of the monitor height guide. The short version is that the top of the glass wants to be about level with your eyes when you sit upright and look straight ahead, and the fix is often just removing a riser or that stack of books rather than adding anything. A screen that is too close and too high is working both your eyes and your neck at the same time, and neither correction costs a cent.

Turn the monitor down

Here is the free fix that the people selling lights have no reason to mention: turn your monitor’s brightness down. The reason is contrast, and OSHA names it directly on its workstation-environment page:

“High contrast between light and dark areas of the computer screen, horizontal work surface, and surrounding areas can cause eye fatigue and headaches.”

The thing that tires your eyes is not the screen’s brightness in absolute terms — it is the size of the gap between the bright panel and the darker room around it. A monitor cranked to maximum in a dim room is a lit rectangle in a cave, and your eyes re-adjust every time your gaze crosses the bezel from screen to desk and back. You can close that gap from either side: bring the room up, or bring the panel down. Bringing the panel down is the one that costs nothing and takes ten seconds in a settings menu.

A rough field test, since the brightness slider has no obvious right setting: if an all-white document on your screen looks like a lightbulb rather than a sheet of paper, the monitor is brighter than the room around it wants. Ease it down until the white reads like paper on the desk beside it. This does nothing to the resolution or the colour — it only narrows the contrast gap OSHA is describing, from the half of it you control for free.

Bringing the room up is the other half, and that is where the light-level question genuinely lives — whether to add ambient light, a task lamp, or a bar behind the screen, and how bright any of it should be. We keep that on its own pages on purpose, because it is where the sources actually disagree. Start with lighting for eye strain for the lux debate itself, the best monitor light bars if the gap you can see is specifically between a bright screen and a dark wall, and color temperature for a home office for the warm-versus-cool question, which is separate again from both brightness and contrast. This page’s one contribution to that whole conversation is the half nobody sells you: your panel has a brightness slider, and lowering it is free.

Put the free levers in order

Nothing on this page needs a purchase, so there is no reason to try them one at a time over weeks. Do all of them in an afternoon and see what is left. Set the 20-20-20 look-away as a timer if you need to, and let it also be your cue to blink and stand. Slide the screen back to somewhere in the 20–40″ band and scale the text up if it got small. Set the top of the screen at or just below your eye line so your head sits balanced over your spine rather than tipped back or forward. Then ease the brightness down until the white on the screen reads like paper, not a lamp.

If you are setting the whole desk up from scratch rather than tuning an existing one, the order to do it in is on the ergonomic desk setuppage; eye comfort largely falls out of getting the chair, the desk height and the screen’s distance and height right, which are the first few steps anyway. What is left after all of that — if anything is — is the room’s light level, and that is the one thing on this topic we will not settle for you in a sentence.

What this page is not

None of this is medical advice, and it is worth being clear about who is writing it. Stephen is a home-office enthusiast who reads standards documents and manufacturer spec sheets — not an optometrist, not an ergonomist, not any kind of clinician. What this page does is report what occupational-safety bodies have published about focus distance, screen distance and screen height, and contrast, and quote them directly so you can check the source yourself.

What it deliberately does not do is diagnose anything, promise relief, or suggest that a break schedule or a lower brightness setting is a treatment for a condition. Tired eyes at the end of a long screen day are ordinary, and the fixes above are cheap enough to be worth exhausting first. But eye strain that persists, that arrives with headaches or blurred or double vision, or that does not ease when you change how and where you work, is a conversation for an optometrist — someone with a license and an eye chart, who can check things about your vision that no posture rule or brightness slider addresses. If that is you, the free fixes here are a sensible thing to have already tried, not a reason to skip the appointment.

Everything above is read off published guidance and cited below. We have not tested any of it on anyone, because measuring people is not what this site does. What we can tell you is that the free levers on this page — look away, blink and break, set the distance, set the height, and turn the panel down — are drawn straight from the sources, cost nothing, and are worth working through before anything on this site with a price tag.