Screen time and your eyes: what the evidence says

By four o'clock your eyes feel like sandpaper

You start the day fine. By mid-afternoon the laptop text swims, your eyes feel gritty, and there is a dull ache behind them. At the weekend, away from the screen, they are fine again. Most people with that pattern worry that the screen is damaging their eyes. The evidence says it is not, but it is doing something, and the something is fixable.

Healthify NZ calls this digital eye strain and lists the usual symptoms: blurry or double vision, dry, red or irritated eyes, eye fatigue and headaches, plus a stiff neck and shoulders from posture. It also states that there is no proof long-term computer use causes permanent eye damage. The American Academy of Ophthalmology is blunter: the idea that screens permanently damage eyes is not true.

Blinking is the real problem

The AAO reports that we normally blink about 15 times a minute, and that studies show we blink only about 5 to 7 times a minute while using computers. Healthify NZ adds that screen users also take more partial blinks. Each full blink spreads a fresh layer of tears, including the oil from glands in your eyelids that stops the tears evaporating. Fewer, shallower blinks mean a drier, less stable surface and, by late afternoon, that sandpaper feeling.

This is why screen strain and dry eye overlap so much. If your eyes are gritty every work day, our guide to what dry eye is explains what is going on in the tear film, and a dry eye evaluation can tell whether screens are the whole story or just the trigger. The other common culprit is a prescription that is not quite right for screen distance, which an eye examination picks up.

The fixes are habits, not products. Healthify NZ suggests the 20-20-20 rule: every 20 minutes, look at something about 20 feet (6 metres) away for 20 seconds. The AAO simply says to look up and away at a distant object regularly. Treat it as a habit that helps most people, not a proven treatment. Beyond that:

• Blink on purpose. Healthify NZ suggests ten full blinks after about 20 minutes of screen time.
• Put the screen about an arm's length away with the upper edge at or just below eye level, so you look slightly down (Healthify NZ, AAO).
• Match screen brightness to the room, cut glare from windows and overhead lights, and use a matte filter if reflections are a problem (AAO).
• Use lubricating drops when your eyes feel dry, and a humidifier in dry, warm rooms (AAO).
• Give contact lenses a break on long screen days and wear glasses instead (AAO).
• If symptoms persist, see an optometrist. The AAO notes that glasses set for screen distance can help, and Healthify lists uncorrected vision and presbyopia among the causes of strain. Our posts on solutions to computer eye strain and keeping your eyes comfortable at work have more set-up tips.

The blue light question

Blue light is part of ordinary daylight as well as screen light. The AAO's position, updated in October 2026, is that the studies showing blue light damage used cells in dishes and animals under conditions that do not match real screen exposure, that so far the evidence shows no meaningful link between blue light and damage to human retinas or macular degeneration, and that blue light from computers will not lead to eye disease. It also says the discomfort of digital eye strain is not caused by blue light, and that blue-light-blocking glasses are not necessary.

A 2023 Cochrane review of 17 trials reached a similar place: blue-light filtering lenses may not reduce short-term eyestrain from computer work, and the sleep results were inconclusive. Where screens do affect you is sleep timing. The AAO says evening screen light can disrupt the body's circadian rhythm and slow melatonin, and suggests night mode and no screens for one to two hours before bed; Healthify NZ says at least an hour. The full picture, including when a filter coating is still a reasonable preference, is in our guide to blue light glasses and the evidence.

Children, near work and short-sightedness

For children the question is different. The worry is not strain but myopia, or short-sightedness, where the eye grows too long and distance vision blurs. The AAO says there is no proven direct link between screens and myopia, but that children who spend more time indoors on near-focused activities such as computer work, video games and reading have higher rates of myopia than children who spend more time outdoors. It also states that there is no evidence screen use harms children's eyes or their developing visual systems.

Outdoor time is the strongest lever. The AAO's 2021 clinical statement says strong evidence supports that outdoor time delays or prevents the onset of myopia, citing a meta-analysis in which each additional hour outdoors per week was associated with a 2 percent reduction in the odds of childhood myopia. The National Eye Institute says children who spend more time outdoors are less likely to be short-sighted, though the reason is not yet clear. The evidence on near work itself is less tidy: the same AAO statement calls the results inconsistent.

Why it matters is the later risk. The AAO notes that higher myopia raises the chance of retinal detachment, cataract and glaucoma in adult life. Our guide to what myopia is covers the condition, our post on whether digital devices cause myopia gives the practice's view, and myopia control explains the options the practice fits if a child's prescription is climbing.

What New Zealand guidance says about screen time

The Ministry of Health's Sit Less, Move More, Sleep Well guidelines for under-fives say to discourage screen time for children under two and to limit it to less than one hour every day for children aged two or older, adding that less is better. Healthify NZ's advice for school-aged children is to try to keep recreational screen time under two hours a day, with at least an hour of physical activity, and to switch screens off at least an hour before bed. These are general health guidelines, not eye guidelines, but outdoor play does double duty for growing eyes.

When an optometry appointment is the wrong place

Screen strain comes on over hours and clears with rest. Symptoms that do not fit that pattern are not screen strain. Call 111 or go to the nearest hospital emergency department for sudden loss of vision, a shadow or curtain across part of your vision, flashes of light with a sudden shower of new floaters, a chemical splash (Healthify NZ says flush with clean running water for at least 15 minutes first), a red and painful eye with light sensitivity, or any injury to the eye. Do not drive yourself.

See your GP first for headaches that wake you, headaches with nausea or weakness, or a red eye with a severe headache, which the NHS lists as reasons for urgent care rather than an eye check. A persistent headache with no visual pattern is a GP matter too. For the ordinary afternoon ache, dryness and blur, an optometrist is the right first call, no referral needed, and Healthline is free on 0800 611 116 if you are unsure at any hour.