Doctors Explain the Truth Behind 11 Popular Eye Myths

Why eating more carrots won't give you super sight.

ByABC News
October 26, 2009, 2:09 PM

Oct. 27, 2009— -- Reading this -- no matter how large or small you've set the font size, no matter how dark the room is -- will not permanently damage your eyes.

And the number of carrots you eat isn't likely to affect how well you can read this either.

Many of us have gotten advice growing up about how we can protect our eyes, but much of this advice would be better off going the way of those thick frames you wore to school in the third grade.

You may know that crossing your eyes too many times won't get them stuck that way, but you may think that reading in a dimly lit room will put you on the path to early nearsightedness.

So, keep your eyes on your brightly lit monitor -- it won't do more than perhaps some temporary eyestrain.

With the launch of our OnCall+ Eye Health section, we're going to take a closer look at 11 of these eye myths, and dispel them -- or explain what truth there may be behind them.

Answer: Myth

Squinting may be a sign that you need glasses, but it isn't going to make your need for glasses any worse.

"You can squint all you want," said Dr. Jay Pepose, an ophthalmologist with the Pepose Vision Institute in St. Louis and an OnCall+ contributor.

"Squinting is an attempt to make the pupil smaller -- it lets in less light," said Dr. Richard Rosen, director of ophthalmology research at New York Eye and Ear Infirmary. "By closing your lids together it further enhances your focus."

For this reason, squinting can help someone who might need glasses see better.

"Squinting suggests that you actually have a refractive error [where the eye cannot bend light correctly, resulting in blurry vision -- such as near- or farsightedness], and this is how someone can get around wearing glasses," said Dr. Kenneth Chang, a comprehensive ophthalmologist at the Massachusetts Eye and Ear Infirmary.

People who squint a lot aren't permanently damaging their vision, but there are some side effects:

"What it does, it gives you a headache sometimes because it [involves] contraction of the muscles of your face," said Rosen.

"In low light the pupil is enlarged, so whatever defects there are in the lens…are not corrected," said Rosen. "When it's bright, you have a much greater depth of focus."

So, more outside light can certainly help you see better. At the same time, though, your retina is not damaged by the high amount of light that is let in by an expanded pupil in the dark.

Similarly, having to focus on a smaller area is likely to cause strain on the eyes, but not lasting damage.

"Basically, it's getting light to the retina and getting it in focus," said Rosen.

"If a tear film is a little on the dry side from not blinking sufficiently…then the quality of vision suffers," said Rosen. "It's sort of a temporary phenomenon."

Some of the strain can be avoided, Chang said. If you are looking at something up close, it's a good idea to take breaks and look into the distance.

"I don't think people were meant to be looking at a computer screen all day long," he said, but "it's not going to cause long-term damage."

He said children may sit close to the screen because they can. "You have more of a range of accommodation and you can sustain it for long periods of time."

Of course, it may also signal a problem.

"If a kid is doing that, it may be that they need a pair of glasses," said Chang.

"The important thing is that some eye conditions can definitely be passed down," said Chang.

"Things like glaucoma are definitely inheritable," he said. "That really reinforces the fact that it's generally good to get a general eye exam."

Chang said some problems are gray areas -- combinations of inheritance and environment -- such as refractive errors.

Studies show that problems such as nearsightedness and farsightedness seem to have some relation to whether a parent had the problem.

Of course, some vision problems have nothing to do with genetics.

"Cataracts is an age-related degeneration of the lens -- that's something that happens to everybody," said Chang.

But at the same time, cataracts, like many vision problems, can be fixed.

Cataracts, a clouding of the lens caused by the folding of proteins, can be removed to fix the problem.

"There's a lot of research now on preventing cataracts," said Moscot. But for other ailments, preventatives are known.

Many of the eye ailments that affect people when they age can be eased by following general health advice. A balanced diet can play a role in preventing some problems, as can giving up smoking. Rosen added that controlling cholesterol and sugar levels could help as well.

Of course, not all problems can be fixed completely. Moscot said that for many eye ailments, he tells his patients that their options are limited to LASIK laser eye surgery and glasses.

"In America it's not an issue, because our diets have plenty of vitamin A," said Moscot.

Some foods can help eyes, however.

Dark green vegetables, such as spinach and broccoli, for example, contain lutein, which is found as a yellow spot in the retina, called the macula.

Rosen explained that these nutrients -- which can also be found in egg yolk -- can protect the macula, and may play a role in preventing macular degeneration, a condition in older adults where they lose vision in the center of the eye.

"It's probably important to encourage people to eat those sorts of foods," he said.

"Typically in adults the system is pretty rigid," said Moscot.

"Focusing difficulties and convergence issues can be improved with eye exercises," he said, but noted that "it does take a commitment and it does take time. In some adults those exercises are helpful, but not all and those are variable."

However, eye exercises that are promoted as helping people get rid of glasses -- known as Bates exercises -- have not been shown to help.

"It's not a scientifically supported method," said Moscot.

Rosen said that while vision does deteriorate -- and exercises will not reverse that -- the exercises may have an effect on utility.

"A lot of it is learning how to use the vision that you have," he said.

An example, Rosen said, is that someone who had a defect in the center of the lens may be aided if they learn to look through other parts.

Rosen said he had some patients who are able to function with 20/400 vision (20/20 is optimal, 20/200 is legally blind).

"A lot of it is how you're able to utilize that sensory input that you get from the eyes," he said. "It may help them to utilize the vision they do have, especially if they've lost some vision."

With age, peoples' eyes deteriorate, and so, someone who needed reading glasses at 40 is likely to need a stronger prescription for them at 50 -- whether they've actually been using glasses or not.

"Everybody does need stronger and stronger reading glasses -- it's inescapable," said Rosen.

In this case, the out-of-focus world that develops over time is due to the growing of the lens of the eye -- the only part of the eye that continues to grow significantly, and a process that prevents the eye from accommodating as easily as it did when one was younger.

But while trying to focus without glasses may strain your eyes, it will not cause lasting damage. While a person may squint in an attempt to see better, the eye itself will not be affected.

In the end, the primary side effect of not wearing glasses is likely to be the temporary one that accompanies accommodation -- excessive squinting is likely to give someone who typically wears glasses a headache.

"Eyeglasses help you see better," explained Chang. "By wearing glasses your vision doesn't get worse faster, and by not wearing them, you're doing your vision a disservice."

When a child's vision develops, problems with crossed or lazy eyes can become permanent.

The reason, said Rosen, is some cells responsible for fusing the images you see with each eye are responsible for a three-dimensional image, and "If, early on in life, those cells aren't stimulated, they never develop," he said.

"The earlier you recognize these things, you enhance the person's chances for stereo vision and for depth perception," said Rosen. "If you recognize there's a weakness in one eye early…then they will start patching the good eye [in order to strengthen the weak eye]."

Many nursery schools have routine screenings of children, but some say those are inadequate.

"School screenings can be very deceptive," said Moscot, noting that some school nurses are not properly trained to perform a full eye exam and some children will cheat by peering at the charts beforehand.

"When they come to an office, there's objective tests we can do better than reading an eye chart." A lot of things are missed in these screenings," he said. "But they're better than nothing."

Moscot also said that family medical history can have an impact on when the first eye exam should be done.

"Typically, when there's a family history of an eye problem or a strong prescription, we like them to be checked before a year old," he said, but noted that for some, "that's a state of thinking now -- that any child should be examined in the first year of life."