Oh oh myopia

Why do we get myopia and how can we slow it down?

Myopia, or near-sightedness, is when our eyes cannot see distance clearly. Our eye is like a camera. When the light focuses exactly on the film in the back of the camera, you get a clear photo. If the camera is too long, the image will focus in front of the film and you get a blurry photo. Similarly, if our eyeball is too long, the image focuses in front of the film- called retina in the back of our eyes- and it’s blurry. Myopia is when the eyeball is too long and mis-matches the power of the eye. As a result objects far away appear blurry.

Why does the eye ball grow longer? It turns out that the growth of the eye ball is regulated locally in the retina. When we see things clearly, our eyeball knows that this is a good match and does not grow much. When images are always falling a little behind the retina as happens with looking at things close up, the retina realizes that it needs to grow just a little more toward the back so the image can fall on it again. Human eyes are not designed to look at things close up for prolonged periods of time. The intense near demand imposed by modern education gives a constant signal to the retina to stretch more and more like a water balloon, leading to myopia. This stretching not only makes far away blurry, but also increases the risk of forming retinal holes and retinal detachment down the road.  

diagramofMyopia

It is commonly accepted that myopia is due to a combination and interaction of genes and environment. Many people are near-sighted and need to wear glasses to see distance clearly. Whereas this is a common finding in school aged children and adults, it is actually quite rare in children younger than 5 years. In fact, majority of kids at 5 years of age have almost no refractive error; if anything, they are slightly hyperopic, about +1.00 D. If we were to live like humans 5000 years ago, that is, spending most of the waking hours farming and hunting, then everyone would stay at this state throughout their lives without myopia. In fact, in Amazonian tribes where school education is not as common or as involved as say in Boston, MA, only 1.6% of people have myopia and the rest of the villagers see distance perfectly well without the need of glasses. The high demand of reading in modern education is a strong environmental factor that stimulates the growth of the eyeball. In some Eastern Asian countries such as China and Japan, prevalence of myopia is as high as 86% in college populations. But of course not every kid at school develops myopia. In addition to individual behavioral and environmental differences, genes play a role too. Kids with both parents being myopic have a much higher chance of developing myopia than those with neither parent being myopic. There are also a small percentage of people with very high myopia that is due almost entirely to genes, but these are beyond the scope of this article.

How would you know if your kids are becoming myopic? Some will complain of blurriness and cannot see the board when teacher writes on it. Often though, kids do not know they are not seeing well, and they may think everyone is seeing that way. But common signs include squinting when watching TV, or reluctance to play outside when distance vision is the primary demand. It is important to have a comprehensive eye exam at an eye doctor’s office for every kid 3 years of age, right before starting K, and annually thereafter. If everything is alright, then once every 2 years is a good frequency to visit eye doctors. But if they develop myopia, then a comprehensive eye exam every year is needed.

What can you do to correct myopia? The most common approach is to wear Rx glasses. There is a misconception that wearing glasses will make myopia get worse. In fact, the opposite is true. Studies have shown that not correcting, or under-correcting myopia will make myopia progress more quickly. When kids get older and capable of taking care of contact lens, contact lens is also an option. A contact lens is a small thin piece of plastic gel lens that is placed on the surface of the eye. Contact lens is great for kids who play sports or those who prefer their looks without glasses on. The con for contact lens is that you have to be careful about hygiene and follow instructions, otherwise may risk infections to the eye. I will talk about contact lens in a separate article. For adults, a laser procedure called LASIK can correct myopia and allow patients clear vision without glasses. This is a subject deserving a separate article.

So what can you do to prevent or slow the progression of myopia development? Well we cannot change our genes, but there are environmental and behavioral measures that we can modify. Below are some of the things to try at home.

  1. Practice visual hygiene. This means to for every hour of near work, be it at computer or reading a book, look off at 20 feet away for 20 seconds.
  2. Improve lighting. Dim light causes more error and blur which can lead to more growth of the eyeball and myopia.
  3. Spend more time outdoors. Recent research has shown that spending more time outdoors significantly slows the progression of myopia, even if what you do outdoors is to read!

How about treatments that slow myopia progression? Researchers have looked into a number of technologies and drugs, and the most effective means so far appear to be OrthoK and low concentration atropine eye drops. OrthoK is a type of contact lens. It is unique in that it is worn at night instead of the day time. Not only does it correct vision so that kids can see distance clearly during the day without any glasses or contact lens, but it actually significantly reduces the speed myopia develops. Low dose atropine eye drop is similar in efficacy compared to OrthoK in slowing myopia development, and it is easier to use as you are not dealing with lens care and hygiene; but the eye drop itself does not provide refractive correction, so kids will still need to wear glasses during the day to see well. Of note is that both treatments only slow myopia development, but do not reverse existing myopia or stop myopia development all together.

As you can see, myopia is a common eye problem that can be corrected by various treatments. And for kids whose eyes are still growing, there are ways to slow the progression of myopia. At this age of smart phones and pads, kids are more prone to developing myopia at an earlier age. For their eye health and quality of life, it is worth taking measures to prevent it, treat it and slow its development if it has already happened.