Common eye and glasses myths: what's true and what isn't

Most popular beliefs about eyes and glasses go wrong in one of two predictable ways: they either blame habits that cause only temporary strain, or trust things that offer no real protection. According to the American Academy of Ophthalmology (AAO), wearing glasses does not weaken eyesight, reading in dim light or sitting close to the TV does not cause lasting damage, and the blue light from screens has not been shown to harm the eye. On the other hand, a dark lens is no proof of UV protection, thin clouds do not block ultraviolet rays, and sharp eyesight does not necessarily mean healthy eyes. This guide goes through the most common myths one by one, explains where each comes from, and sets out what actually protects your sight.

Myths about wearing glasses

The most widespread belief is that glasses make the eyes "lazy", so the more you wear them, the stronger the prescription you will need. It sounds logical, because many people notice that the world looks blurrier without glasses than it did before they got used to them. But nothing in the eye has changed: you have simply grown used to a sharp image, so the blur you used to live with now stands out. A prescription is set by the length and shape of the eye, the curve of the cornea and, for close-up focus, the flexibility of the eye's natural lens; ordinary glasses alter none of them. If a prescription changes over the years, that is the natural course of things, such as nearsightedness progressing in a growing child or the near-focusing changes that usually begin after age 40, not a side effect of the lenses.

• Myth: glasses weaken the eyes or make you dependent on them. Fact: the AAO states that wearing glasses does not make eyesight worse or make you dependent on them. In adults, going without them does no damage either; it just means more blur and more strain.
• Myth: wearing someone else's glasses, or an old prescription, damages the eyes. Fact: in adults, the wrong lenses cause blur, headaches and tired eyes, but no lasting harm. Children are different: uncorrected or under-corrected nearsightedness in a child may speed up its progression, and when glasses are treating a lazy eye or crossed eyes, the exact prescription is part of the treatment. Keep your child's prescription up to date and follow the eye doctor's instructions.
• Myth: eye exercises can get rid of the need for glasses. Fact: the AAO says eye exercises will not improve or preserve vision or reduce the need for glasses. Nothing in them can change the shape of the eye. Specific exercises do have a place in treating some eye-coordination problems, but only when an eye specialist prescribes them.

Ready-made reading glasses deserve a note here: for many people over 40 who see well at a distance, whose two eyes need a similar strength and who have no significant astigmatism, they are a reasonable, harmless option for occasional reading. They are no substitute for an eye exam, though, because some silent eye diseases become more common at this same age.

Myths about reading, screens and light

Many of the warnings we heard as children confuse discomfort with damage. Reading in poor light, sitting near the television or staring at a phone for hours can all leave the eyes tired, dry or sore, but the American Academy of Ophthalmology points out that this strain is temporary and fades with rest; it does not wear the eye out.

• Myth: reading in dim light ruins your eyesight. Fact: it makes the eyes work harder and can cause fatigue and headaches, but it does not cause permanent damage. Good light is about comfort, not protection.
• Myth: sitting close to the television harms children's eyes. Fact: there is no evidence that it causes damage, and children can focus up close more easily than adults. The habit is still worth noticing, though, because a child who always moves closer to the screen may be nearsighted and need an eye exam.
• Myth: blue light from phones and computers damages the retina. Fact: the AAO says there is no scientific evidence that the blue light from digital devices harms the eye, and it does not recommend blue-light-blocking glasses for screen use. Late-night screen light can make it harder to fall asleep, however, so dim the screen or switch on night mode before bed.
• Myth: using a phone in the dark damages the eyes. Fact: the contrast between a bright screen and a dark room is tiring and uncomfortable, but not harmful in itself. Leaving a soft light on in the room makes it far more comfortable.

What really tires the eyes in front of a screen is the way we use it. People normally blink about 15 times a minute, and studies show that the rate drops sharply while staring at a screen, often to half or less, so the surface of the eye dries out. The effect is stronger in dry, air-conditioned rooms like most of our homes and offices. The simple fix the AAO recommends is the 20-20-20 rule: every 20 minutes, look at something at least 20 feet (about 6 metres) away for at least 20 seconds. The AAO also advises making a conscious effort to blink fully.

Myths about sunglasses and the sun

In a country where the sun is strong for most of the year and sand reflects extra light toward the eyes, sunglasses are protective equipment, not just an accessory. That makes the myths around them more costly than most.

• Myth: the darker the lens, the better the protection. Fact: tint reduces brightness, but UV protection comes from a filter in the lens material, not from its colour. A dark lens without that filter can even backfire: it gives a false sense of protection, and because the glare drops behind it you stop squinting and open your eyes wider, letting more ultraviolet light reach them.
• Myth: expensive sunglasses protect better than cheap ones. Fact: a higher price buys design, materials and optical quality, not UV blocking. The AAO notes that inexpensive sunglasses labelled 100% UV protection can be just as effective as pricier ones; what matters is a genuine label from a reputable seller, not the price tag.
• Myth: you don't need sunglasses on a cloudy day. Fact: ultraviolet rays pass through haze and thin clouds, so the exposure continues even when the sun feels gentler.
• Myth: a quick look at the sun, or at an eclipse, is harmless. Fact: looking directly at the sun, even briefly, can burn the retina, and the damage can be permanent. Ordinary sunglasses, however dark, are not safe for watching an eclipse.

The practical rule is short: look for a label saying UV400 or 100% UV protection, which means the lens blocks ultraviolet light up to a wavelength of 400 nanometres; choose a category 3 lens for everyday strong sun; and consider a frame that wraps around the face to cut light and dust from the sides.

Myths about everyday eye care

• Myth: eating lots of carrots sharpens your vision. Fact: carrots provide vitamin A, which the eye needs, and a genuine deficiency can cause night blindness. But for someone already getting enough, more carrots will not improve sight or lower a prescription. The story spread largely through Second World War propaganda rather than through research.
• Myth: rubbing your eyes is a harmless habit. Fact: rubbing with unwashed hands carries germs into the eye, and frequent, forceful rubbing is linked to the worsening of keratoconus, a thinning and bulging of the cornea, in people prone to it. When dust or sand gets in, rinse with clean water instead of rubbing.
• Myth: a contact lens can slip behind the eye and get lost. Fact: this is anatomically impossible. A thin membrane called the conjunctiva lines the inside of the eyelids and folds over onto the white of the eye, sealing off the space behind it. A lens can slide up under the upper eyelid, where it may feel uncomfortable; if you can't get it out yourself, an eye doctor can find and remove it.
• Myth: crossing your eyes on purpose can make them stay that way. Fact: the eye muscles relax as soon as you stop. A real, persistent eye turn in a child is a different matter that needs an eye exam, and children do not simply grow out of it.
• Myth: if you can see clearly, your eyes are healthy. Fact: some serious conditions, above all the most common form of glaucoma, cause no symptoms until part of the vision has already been lost. Sharp sight and a healthy eye are two separate things.

That last myth is the most costly, because it delays the exam that would catch a problem early. The American Academy of Ophthalmology recommends that adults with no symptoms or risk factors have a complete baseline eye exam by age 40, when early signs of disease and age-related vision changes tend to appear, and people with diabetes are generally advised to have a dilated eye exam once a year. After that, your eye doctor will set the right schedule for you.

How to tell a myth from good advice

New claims about the eyes circulate every day, from clips promising you can "throw away your glasses" to products sold with a long list of health benefits. A few questions help you judge them before you believe them or pay for them:

• Does the claim promise to remove the need for glasses or lower your prescription? No exercise, supplement or home remedy changes the shape of the eye, so treat that promise with suspicion.
• Does it confuse temporary discomfort with permanent damage? Eyes that are tired after reading or screen time need rest, not fear.
• Does it judge protection by appearance, such as a darker lens, a yellow tint or a higher price? Protection shows on the label, not in the look.
• Who is making the claim? A medical body or an eye specialist is a better guide than someone selling the product being praised.

Whatever the myth, some symptoms should never be waited out: sudden loss or blurring of vision, a burst of new floaters or flashes of light, a curtain over part of your vision, severe eye pain with redness, or any injury to the eye. Each of these calls for an urgent visit to an eye doctor or the emergency department, not a home remedy. The one exception is a chemical splash: rinse the eye under clean running water for at least 15 minutes first, then head to the emergency department. With any other injury, don't rub or press on the eye, and don't try to remove anything stuck in it.