Eye myths fact-checked: what’s true and what isn’t

Most of us heard them as children: ‘Eat your carrots and you’ll see better’, ‘Don’t read in the dark’, ‘Stop crossing your eyes or they’ll stay like that’. Some of these sayings are simply wrong; others contain a grain of truth. Here is a fact check of common eye myths – each with the claim, the evidence and the source.

Carrots: important if you are deficient, no boost for healthy eyes

‘Carrots sharpen your eyesight’

What’s true: Carrots contain beta-carotene, which the body converts into vitamin A – and the eye needs vitamin A to see in low light. According to the World Health Organization (WHO), night blindness is one of the first signs of a deficiency. Deficiency is especially widespread in Africa and South-East Asia. An estimated 250,000 to 500,000 deficient children go blind every year, and half of them die within twelve months.

If you already get enough vitamin A, though, extra carrots will not make your vision any sharper. According to the American Academy of Ophthalmology (AAO), the eye needs only a relatively small amount, which is also found in dark leafy greens, dairy products and fish. An article by three ophthalmology professors in the trade magazine The Ophthalmologist (2026) notes that vitamin A supplements do not appear to change the vision of healthy people. On top of that, the body makes only limited use of the beta-carotene in carrots.

Where the myth comes from: During the Second World War, when British cities were blacked out at night, the Ministry of Agriculture announced in 1940 that eating more carrots should overcome the widespread ‘blackout blindness’. Night-fighter pilot John Cunningham, nicknamed ‘Cat’s Eyes’, also became famous: 19 of his 20 kills were at night – supposedly thanks to all the carrots he ate. Some historians suspect this was a deliberate deception to keep the new airborne interception radar secret. Whether the German Luftwaffe actually fell for it, however, is not known.

Sources: WHO; AAO; Schwartz et al., The Ophthalmologist (2026)

Dim light and the TV: tiring, but not harmful

‘Reading in dim light ruins your eyes’

What’s true: According to the AAO, reading in dim light does not harm your eyes. Good lighting does make it easier to see, though, and your eyes tire less quickly. Lots of small print does not wear out your eyes either, but it can strain them.

‘Sitting close to the TV will ruin your eyes’

What’s true: According to the AAO, sitting very close can strain your eyes or give you a headache, but it does not damage the vision of children or adults. Children are particularly good at focusing on nearby objects, so they may simply find it more comfortable to sit close. The reverse is more interesting: someone who habitually sits right up close to the screen may be short-sighted.

Source: AAO

Crossed eyes: they won’t get stuck – but children don’t outgrow a squint either

‘If you cross your eyes, they’ll stay that way’

What’s true: The eye muscles move the eyes freely in every direction. Looking to the left does not lock your eyes on the left, and pulling a cross-eyed face does not fix them in place either, the AAO explains. A lasting squint has other causes, such as disease, uncorrected refractive error or damage to the muscles or nerves.

‘Children grow out of a squint’

What’s true: This misconception can have consequences. According to the American Optometric Association (AOA), a true squint (strabismus) is not outgrown; without treatment it can even get worse. Because the brain gradually learns to ignore the image from the turned eye, that eye risks permanently weaker vision – a condition known as amblyopia or ‘lazy eye’. Detected early, however, a squint can often be treated well. The AOA therefore advises an examination for any child older than about four months whose eyes do not always look straight. In babies, a fold of skin at the inner corner of the eye or a wide bridge of the nose can sometimes merely mimic a squint – an examination will show which it is.

Sources: AAO; AOA

Glasses and eye exercises: what they do – and what they don’t

‘Wearing glasses makes your eyes weaker’

What’s true: According to the AAO, glasses neither worsen your eyesight nor cause eye disease. Even the wrong lenses do not cause lasting damage, although they can give you a headache or blurred vision, which goes away once you take them off. Conversely, if you need glasses, the AAO says you should wear them – that way you see as well as you can and your eyes do not have to work as hard.

‘Eye exercises can train away short-sightedness’

What’s true: Exercise programmes for refractive errors have been promoted since at least 1912. The AAO reviewed the evidence in 2013: two randomised controlled trials found no benefit for short-sightedness, and there was no evidence that training slows its progression. One study from 1982 is revealing: after an average of 35 training sessions, 17 short-sighted participants could read just over three more lines on the eye chart on average – yet their measured refractive error was unchanged. Possible explanations named by the AAO include learning to interpret blurred images better, motivation, changes in the tear film, or a smaller pupil acting like a pinhole. Nor did the AAO find any evidence of benefit for long-sightedness, astigmatism, macular degeneration or glaucoma. The only risk, it says, is financial.

The AAO does name one exception: with convergence insufficiency, where the two eyes do not work together well when looking at something close, exercises can help.

Sources: AAO (2013, 2026)

Rubbing your eyes: the myth with a grain of truth

‘Rubbing your eyes is harmless’

What’s true: According to the AAO, excessive eye rubbing is associated with keratoconus. In this condition, the cornea thins and bulges into a cone shape, making vision blurry and distorted. It often begins in the late teens or early twenties.

A meta-analysis in the journal Cornea (Hashemi et al., 2020) pooled 29 studies with more than 7 million participants from 15 countries. Keratoconus turned out to be rare – around 1.4 cases per 1,000 people. When the authors looked at possible risk factors, eye rubbing was linked to roughly three times higher odds of the condition (odds ratio 3.1). The link with a family history of keratoconus was even stronger (6.4), and eczema, asthma and allergies also played a role. Observational data like these show an association, but they do not prove that rubbing alone causes the disease.

In practice: If your eyes itch all the time, have the cause looked into rather than rubbing again and again. The AAO explicitly advises people with keratoconus not to rub their eyes and to have itchy eyes – from an allergy, for example – treated by a doctor.

Sources: AAO; Hashemi et al., Cornea (2020)

In brief: screens and the sun

• ‘Screens damage your eyes’: According to the AAO, they do not harm your eyes directly, but long stretches without a break can contribute to eye strain and dry eyes. Looking up roughly every 20 minutes and blinking regularly helps. Read more in our guide Dry eyes and screen work. For children, it is worth taking a closer look: our guide Why myopia is on the rise sums up what studies show about screen time, time outdoors and short-sightedness.
• ‘Looking at the sun is good for you’: A dangerous misconception. Even a brief stare into the sun without suitable protection can permanently damage the retina, up to and including blindness. Ordinary sunglasses and homemade filters offer no protection; only solar filters that meet the ISO 12312-2 standard are safe (AAO).

When to have your eyes examined

Many myths are harmless – some warning signs are not. See an eye doctor if

• a child older than about four months has eyes that do not always look straight,
• a child habitually sits very close to the TV,
• you develop a new squint – it can also develop after a stroke or head injury (AOA); if you suddenly see double, follow the emergency advice below,
• your vision gradually becomes more blurred or distorted, straight lines look wavy or you often need a new prescription – possible signs of keratoconus (AAO),
• you notice any problems with your vision after looking at the sun – in that case, straight away.

Emergency: According to the Swiss Heart Foundation, sudden double vision or a sudden loss of sight, often in one eye only, can be a sign of a stroke – as can sudden, often one-sided weakness of the face, an arm or a leg, difficulty speaking, severe dizziness or an unusually severe headache. Call the emergency number immediately – 144 in Switzerland – even if the symptoms quickly pass.

Our online eye test gives you a first idea of how sharply you see at a distance; it does not replace an examination. At My Laser Vision in Wallisellen, our ophthalmology services include a children’s check-up, squint diagnostics and corneal topography, among other things.