Misconceptions about your eyesight

There are so many misconceptions about your eyesight. Here Mark Blankstone explores some of the myths

MYTH #1: IF YOU CROSS YOUR EYES, THEY’LL STAY THAT WAY.

It’s a myth that your eyes will “freeze” if you cross them for too long. Crossed eyes occurs when your eyes don’t look the same way at the same time. There are six muscles attached to each of our eyes that, guided by signals from the brain, control their movements. When your eyes don’t align, the brain gets two different images. Over time, this can cause more serious vision issues. That’s a real problem, but it’s not caused by making your eyes cross on purpose for short periods of time.

MYTH #2. EATING CARROTS WILL HELP YOU SEE IN THE DARK.

Well, carrots certainly aren’t bad for your eyesight. They contain beta carotene which your body converts into vitamin A, a crucial vitamin for vision. But carrots don’t do anything exceptional for your nighttime vision.

MYTH #3: THE BIGGER YOUR EYES, THE BETTER YOUR EYESIGHT.

When you’re born, your eyeballs are approximately 16 millimeters in diameter, reaching 24 millimeters as an adult. But your eyes getting larger does not necessarily mean that your vision is getting better. In fact, excessive growth in human eyes can cause myopia, or nearsightedness. If the eyeball is too long, the eye’s lens can’t focus the light in the right part of the retina to process images clearly.

MYTH #4: PUPIL DILATION OCCURS ONLY IN RESPONSE TO CHANGES IN LIGHT.

We all know that pupils contract in light and dilate in darker conditions. But did you know that pupils also respond to changes in our emotional and mental states. Sexual arousal, solving a complicated mental math problem, fear, and other cognitive and emotional events can provoke changes in pupil size, though the precise reasons why are not yet clearly understood.

MYTH #5: UV RAYS CAN ONLY DAMAGE EYES WHEN THE SUN IS SHINING.

Even on cloudy and foggy days, ultraviolet (UV) radiation can cause eye damage. The rays can be reflected off of water, sand, snow and shiny surfaces. So make sure to keep your 100 percent UV protection sunglasses handy whenever you are out and about. Years of exposure can increase your risk of developing cataracts, a clouding of the eye lens that can cause vision loss.

MYTH #6: WEARING GLASSES TOO MUCH CAN MAKE YOUR EYESIGHT WORSE.

This myth suggests that over-reliance on glasses for common vision problems like nearsightedness, farsightedness, and astigmatism will weaken or damage eyes. That’s not true, nor will your eyes be damaged by wearing glasses with a prescription that’s too strong—though it may give you a temporary strain or headache.

However, children should still be given the correct prescription. A study in 2002 found that giving children glasses with a prescription that is too weak can increase their myopia, while giving the correct prescription “reduces the progression of myopia.”

MYTH #7: READING IN DIM LIGHT WILL DIMINISH YOUR EYESIGHT.

How many of you recall your parents telling you to “put some light on the subject” when you were curled up with a good book in dwindling daylight? Having more light can certainly help you see better, because it makes it easier for you to focus. But while reading in semi-darkness may put a temporary strain on your eyes, it’s not going to permanently damage your eyesight. Recent studies indicate not getting enough daylight in general, however, may have a detrimental effect on vision.

MYTH #8: IF YOUR PARENTS HAVE BAD EYESIGHT, YOU WILL, TOO.

You might, of course, because some eye problems are genetic. But there’s no guarantee that we will develop the same vision impairments as our parents. One study found that if both parents are myopic, there’s a 30 to 40 percent chance that the child is. If only one parent is myopic, the child has a 20 to 25 percent chance, and it’s down to 10 percent for kids with non-myopic parents.

MYTH #9: TOO MUCH SCREEN TIME WILL DESTROY YOUR EYESIGHT.

Optometrists frequently debate this topic, but most agree that it’s not too damaging for most people. Having said that, more and more people are complaining of symptoms like dry, irritated eyes, headaches, eye strain and difficulty focusing after prolonged periods of screen time. The American Optometric Association (AOA) defines this group of symptoms collectively as Digital Eye Strain—which can be further exacerbated by trying to focus on small screens such as tablets or phones. The AOA recommends following the 20-20-20 rule to remediate the effects of screen time: Every 20 minutes, take a 20-second break to look at something 20 feet away.

MYTH #10: THE RIGHT “VITAMIN COCKTAIL” CAN PREVENT VISION DECLINE.

Recent studies don’t support the notion that the right combination of vitamins can keep your eyesight from diminishing. One particular study showed that antioxidant vitamins may help slow the progression of macular degeneration, one of the most common causes of vision loss as we age. But for people not already suffering from the disease, preventative use of such vitamins didn’t appear to make a significant difference. Perhaps an effective vitamin cocktail will be discovered one day, but so far, there’s no proof that it works.

MYTH #11: DYSLEXIA IS LINKED TO VISION PROBLEMS.

A recent study from Bristol and Newcastle Universities in the UK found that children with dyslexia were no more likely than others to suffer from common vision problems like myopia, far-sightedness, squinting or focusing problems.

MYTH #12: IF YOU DON’T TREAT LAZY EYE WHEN YOU’RE A SMALL CHILD, YOU’LL HAVE IT FOREVER.

Lazy eye, or amblyopia, occurs when nerve pathways between the brain and the eye aren’t properly stimulated, causing the brain to favor one eye over the other. The weaker eye tends to wander, and eventually the brain might ignore signals received from that eye. While doctors say that the sooner it’s treated the better, there are an increasing number of remedies (including Tetris) that can help adults as well.

MYTH #13: BLIND PEOPLE SEE ONLY DARKNESS.

According to a foundation for the blind in the USA, only 18 percent of people who have visual impairments are totally blind. Most are able to differentiate between light and dark.

MYTH #14: HUMAN VISION IS THE SAME IN SPACE AS IT IS ON EARTH.

Actually, NASA scientists have found that space can impair our vision, though they still aren’t sure why. A study of seven astronauts who spent more than six months on the International Space Station noted that all experienced blurry vision during and for months after their space mission. The researchers hypothesized that the shift of fluids toward the head that can occur in microgravity might have something to do with it. Now, NASA is following up with a study that will track the vision of crew members during and after long space missions to try and determine exactly why these vision changes occur in space.

MYTH #15: PEOPLE WHO ARE COLORBLIND CAN’T SEE COLOR.

The human eye and brain work together to interpret color from light, and each of us perceives color slightly differently. We all have photopigments—color-detecting molecules—in cone-shaped cells inside our retinas. But people who suffer from hereditary colour blindness have defects in the genes that direct production of photopigments. It’s quite rare for someone not to see color at all, however. It’s more common for colour blind individuals to have difficulty differentiating between certain colors, like red and green, or blue and yellow. And while color blindness is far more common in males than females, it does affect a small percentage of women.