Digital eye strain

It does not damage your eyes

Start with the reassurance, because this subject attracts a good deal of alarm. The Health and Safety Executive puts it plainly: display screen work does not cause permanent damage to the eyes.

What prolonged screen work does cause is tiredness, discomfort, headaches and — occasionally — a temporary blur for distance afterwards, which settles. Those are real and worth doing something about. They are not the early stages of anything.

It goes by several names: digital eye strain, computer vision syndrome, visual fatigue. They describe the same thing.

What actually causes it

Older explanations put the blame on the screen itself — that text made of pixels gives the eye nothing stable to focus on, so it hunts back and forth and tires. That was a reasonable description of a cathode-ray monitor flickering at low refresh rates. It is not a useful description of a modern screen, and it points attention at the wrong thing.

Three things do most of the work.

Blinking stops. Blink rate falls substantially during concentrated screen work, and the blinks that do happen are often incomplete. The tear film is what keeps the front of the eye smooth and comfortable, and it depends on being spread by blinking. This is why screen discomfort so often is dry eye rather than a focusing problem, and why it responds to the things that help dry eye.

Focus is held at one distance for hours. The muscles that focus the eye for near work are doing sustained effort with no break. That is tiring in the same way that holding any posture is tiring, and it is why the eyes feel slow to shift to distance afterwards.

The setup fights the eyes. Glare from a window or an overhead light, a screen brighter or dimmer than the room around it, a screen too close or at the wrong height, small text, and a position that forces the head into an awkward angle all add to the load. Neck and shoulder ache usually travels with eye strain for this reason, and treating the two separately misses the point.

The symptoms

Tired, aching or sore eyes; dryness, grittiness or watering; blurred vision that clears on blinking or on looking away; headache, usually across the forehead or behind the eyes; difficulty shifting focus between screen and distance; and neck, shoulder or back ache.

Two things sometimes listed as symptoms of screen strain do not belong there. Double vision and disturbed colour vision are not features of ordinary digital eye strain, and either warrants an eye examination rather than a change of monitor. Nor does screen strain cause pain in the eye, light sensitivity or loss of vision — those point elsewhere.

What helps

Breaks, which are the single most effective measure. The common formulation is to look at something around twenty feet away for about twenty seconds every twenty minutes. The precise numbers matter less than the principle: short, frequent changes of focus beat one long break, and the eyes recover during them. Standing up and moving at the same time deals with the neck and shoulders.

Blinking deliberately sounds trivial and is not. A few full, complete blinks when the eyes start feeling gritty re-spreads the tear film. Positioning the screen slightly below eye level helps too, because a downward gaze exposes less of the eye surface to the air than looking straight ahead or up.

Lubricating drops — ordinary artificial tears from a pharmacy — are genuinely useful where dryness is the main complaint, and more useful than most people expect.

Dealing with the air. Air conditioning, fans blowing across the face and dry heated offices all accelerate tear evaporation. Moving the seat out of the draught is free.

The screen itself

Position it about an arm's length away, with the top of the screen at or slightly below eye level, and tilted back slightly so the gaze is downward.

Put it at right angles to windows rather than facing or backing onto them, and use blinds to control daylight. Match the screen brightness roughly to the room: a bright screen in a dark room is harder work than either on its own. Increase the text size rather than leaning in — leaning in is how a screen problem becomes a neck problem.

Keep the screen clean, which is more significant than it sounds, and consider a matt finish or an anti-glare screen where reflections cannot be designed out.

Glasses, honestly

Older advice says that in most cases glasses need to be prescribed to deal with screen strain. That is not right, and it reverses the order of things. Most digital eye strain is managed by breaks, blinking and setup, and no lens addresses any of those.

There are people for whom glasses genuinely are the answer, and they fall into recognisable groups. Anyone with an uncorrected or out-of-date prescription, who is working harder than they need to. Anyone with presbyopia, where reading glasses are focused closer than a screen sits and varifocals put the intermediate zone in an awkward place — a dedicated pair focused for screen distance can transform a working day. And people with a binocular vision problem that only shows up under sustained near work, which is a reason for an examination rather than an off-the-shelf purchase.

That is the useful question to put to an optometrist: not “do I need computer glasses” but “is anything about my prescription making this harder than it needs to be”. The lens options are covered under choosing glasses.

On blue light filtering lenses and coatings, which are marketed hard for exactly this complaint: the evidence that they reduce eye strain or protect the eye is weak. Someone who finds them comfortable has lost nothing by using them, but they are not the solution to this problem and buying them instead of taking breaks is a poor trade.

The eye test your employer pays for

This is widely unknown and worth knowing.

In the UK, someone who uses display screen equipment as a significant part of their job is entitled to an eye and eyesight test on request, and the employer has to pay for it. It is a full test by an optometrist or doctor, not a screening. The employer can decide how — reimbursing the cost, or sending staff to a particular optician — but not whether.

Glasses are a narrower entitlement. The employer only has to pay where the test shows that special glasses are needed for the distance at which the screen is viewed. If an ordinary prescription will do the job, there is no obligation to fund it — which is a reasonable line, and it is why the distinction between screen-distance glasses and everyday glasses matters.

Asking is the whole mechanism. The entitlement is on request rather than automatic.

When it is not eye strain

Symptoms that do not improve with breaks and a better setup over a few weeks are worth having looked at, as are headaches that are getting worse rather than better, any change in vision that does not clear on blinking, and double vision at any time.

A sight test is the sensible route, and mentioning how many hours a day are spent at a screen changes what the optometrist checks — so it is worth saying rather than waiting to be asked.