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.

Why are your eyes dry?

-All about the glands

Many people come to the eye clinic complaining of dry eye—burning, sandy, foreign body sensation, tearing, and redness. Many don’t complain, but their eyes look dry under slit lamp—a magnifying device eye doctors use to examine eye health. So why are my eyes dry? You ask.

You probably know that our tears are made and secreted by a tear gland, or lacrimal gland. We have a main lacrimal gland that is above the eye, and several smaller glands scattered throughout conjunctiva, the clear membrane that covers the white part of the eye as well lining the inside of the eye lids. These glands produce the water part of the tears, and when you cry, a large amount is produced. This is the water or aqueous layer of the tear film. Do you know that there is another layer covering this water layer and that layer is actually made of fat? It is much thinner than the water layer, but it is there to prevent the evaporation of the water layer, in other words, seal the moisture. Without this fat layer, tear will quickly evaporate, leaving the surface of the eye dry. It turns out, that majority, or 70% of all dry eye cases are caused by deficiency or problem with the fat layer.

meibomian-glands-660x573

So what makes the fat layer of the tear film? Large sebaceous gland inside the upper and lower eye lids make them. These are called Meibomian glands. These are just like sebaceous glands in the skin, making oil and secreting it to lubricate the skin, or in the case of Meibomian glands, seal the moisture on the surface of the eye. The oil is released each time you blink, onto the lid margin via small ducts, then mixes with the tear and forms the outer layer.

You may have heard your eye doctor say to perform warm compress and lid scrub to your eyelids to alleviate dry eye. This is actually the standard first line treatment for mild dry eye. Ever wonder why? The warm compress warms up the oil and makes it more fluid like just like when you heat up butter to make it liquid, then the scrubbing action exfoliates debri and other materials that block the meibomian gland duct opening on the lid margin, allowing the lipid to flow out of the duct to the eye surface. Many people who suffer from dry eye have their Meibomian gland duct blocked, not unlike clogged sebaceous gland of the skin which when inflamed gives you acne. Warm compress and lid scrub can effectively open up those glands again so you get lipid in the tear to make tear film longer-lasting. Some doctors will recommend using baby shampoo, some recommend using mineral oil when doing the scrubbing. As long as you consistently do it at least twice a day for 2-4 weeks, for just 5 min each time, you will experience the difference, even if you just use clean warm water and a clean wash cloth without any additional product. After dry eye is resolved, you want to maintain this routine for once a day every day to keep your Meibomian glands open and happy and keep dry eye at bay.

So why do the Meibomian gland ducts get clogged up? It is not known why, but as we get older, there is more keratinization going on in that ductal area, making the duct opening narrower, which causes some accumulation of the fat at the opening, sometimes ‘capping’ the duct opening. Once that happens, oil can no longer come out and you experience dry eye. Long-term clogging of ducts lead to increased oil accumulation and increased pressure inside the gland, which may cause gland atrophy, which means the gland gets smaller and under functions. If this goes on for long enough, the entire gland can drop out, so no more oil can be produced.

I have an analogy that breast-feeding mums may appreciate. When your milk ducts are clogged, you get engorgement. After painfully massaging, squeezing, warm or cold compressing, you notice your milk production decreases, which you have to pump a whole lot to restore the production, or in some situations, you never get that amount of mild back. Sometimes in addition to engorgement, you can also get mastitis, painful inflammation with fever that is actually quite dangerous. For Meibomian glands, clogged ducts sometimes can also lead to a bump on the lid, or chalazion. The treatment again is warm compress, lid scrub for many days, sometimes weeks to months, to open the duct, allowing fat to come out; or if it’s very severe, a small surgery is needed to drain the fat out. For some people, chalazion can recur, and it is not a pleasant thing to have.

Oh I forgot to mention that all this problem with the Meibomian gland which results in dry eye is called Meibomian gland dysfunction, or MGD for short. When MGD is caused by clogging of duct, it is termed obstructive MGD. In some cases though, the duct is open, but the gland just fails to produce enough amount or quality of fat to lubricate the eye. Why so? It is not clear, but scientists hypothesize that when we get older, our hormones, specifically sex hormones, growth hormone, and IGF-1 decline, and since these hormones drive the sebaceous glands to produce oil, our skin gets dryer, as is our tear less ‘oily’ and more evaporative. It is noteworthy that some people’s Meibomian gland produces too much oil, or oil that is too viscous, which is prone to clogging, leading to MGD and dry eye. Therefore, a healthy Meibomian gland that produces proper amount and good quality oil is key to eye surface health.

What about the water part of the tear? Isn’t the bulk of the tear film actually water? It turns out that dry eye solely due to water or aqueous deficiency is much less common than MGD or evaporative dry eye. One example is Sojgren’s syndrome, an autoimmune condition where the body’s immune system attacks the lacrimal gland (as well as salivary gland), leading to dry eye and dry mouth. But this is a rare disease.

What about artificial tears? You may ask. They certainly are a good substitute if your own tears are drying out too quickly. And I will talk about them in a separate article. Here is the thing though, while they relieve the symptoms for some, for others, they may need to be put in too many times a day to be helpful. This is because whatever is put in the eye, drains out pretty fast into the nose. You know this after you cry, your tears come out of your nose so that your eyes are not flooded. There are all sorts of formulas and some of them stay on the eye for longer than others. But if your own gland is healthy, it will be constantly pumping out good oil to make the tear long-lasting.

So do not forget to blink. We stare at the computer or our phones for too long, and forget to blink. Remember that blinking is necessary to bring out the oil and distribute the tear film evenly across the surface of the eye. So blinking frequently helps the dry eye.

 

Here is how to do warm compress and lid scrub:

  1. soak a clean wash cloth with clean and warm water, semi-dry out the cloth like when you wash your face
  2. close eyes and put the cloth on eyelids till it’s no longer warm
  3. now scrub eye lids along the entire lids while eyes are closed for a few seconds
  4. repeat above and do this for 5 min.
  5. do this twice to four times a day.