What is Myopia?

 

Myopia is often referred to as nearsightedness. An easier way to understand it is how patients perceive the world around them. Essentially, far away objects are blurry, but most with myopia can read things up close just fine! It depends on the level of myopia, so someone who has a mild amount may be able to see things within arm’s reach pretty well. Someone with more severe myopia may have to hold things very close to their face in order to see things more clearly.

Why does it matter to try to reduce children from developing it?

 

The amount of myopia is increasing across the entire world. Some populations have a very low prevalence of nearsightedness while others have exploded in the last decade. One study1 cites that 90% of students enrolled at Taiwan University have myopia!

Apart from the frustrations that nearsighted people face of not being able to see without their glasses or contact lenses, progressive myopia is linked to the development and progression of a number of eye health problems.

The higher the myopia, the more at risk patients are for developing conditions such as glaucoma, cataracts, and retinal detachments.1-2 I will make one note though, all patients will develop cataracts given a long enough timeline! It just depends on when you develop them and how quickly they progress. In my experience, high myopes tend to need cataract surgery several years earlier than other patients.

 

How can we slow the progression of myopia?

 

There are three main methods to aid in slowing down the progression of myopia in children. Two of them involve contact lenses and the third utilizes a compounded eye drop from a pharmacy.

1. Ortho-Keratology (Ortho-K) contacts are a type of rigid contact lens that is worn while you sleep. It works by reshaping the front of the eye, the cornea, to correct for nearsightedness. This is a temporary effect and typically has to be worn nightly to keep the effect going. This type of lens is great for patients who want to slow down their child’s nearsightedness, but it can also be worn by adults who want the convenience of not needing glasses during the day, but don’t want to have LASIK!

 

2. Soft Multifocal contacts are another great option for myopia control. While there are so many multifocal lenses out there, only a few of them work, depending on the way the lens is designed. In our practice, we typically fit children into a daily disposable lens called NaturalVue. This lens is worn during waking hours only, then discarded at the end of the day.

 

3. Finally, atropine eye drops can also be compounded down to a much smaller percentage than is normally available. Atropine is actually the strongest dilating eye drop. When we dilate someone with it, it can last for up to two weeks! This doesn’t sound like a great effect to have to deal with to keep your vision from progressively worsening though. Instead, we take the 1.0% strength and have it compounded at a special pharmacy down to 0.05% (this value are subject to change depending on the most recent data) instead. This reduces the chances of dilation in the eyes and provides the desired effect.

The mechanisms of how myopia control works is still being researched and heavily debated, but the generally accepted mechanism is that as light rays enter the eye, they all focus on the retina at the same speed. Peripheral light rays are not focused differently than central light rays. Because the eye is not perfectly round, but mildly oblong, some light rays are not focused in the correct location.

 

This peripheral light defocus is thought to stimulate the retina to try to grow to focus it on the back of the eye. Here’s a rudimentary drawing to illustrate:

In order for the light rays to focus on retina, we have to place a lens in front of the eye to correctly move the focusing point onto the macula (the X). That’s the point where things are going to be most clear for us!

But when we do that (via glasses, soft contact lenses, etc.), we have also move the other light rays at the same distance. This can further defocus the peripheral light rays outside of the eye. Because the eye wants to try to always have the light in focus, the eye receives signals to attempt to grow the eye longer to try to make things focused again.

Of course the problem here is that the eye has to grow evenly. So in order for the peripheral light rays to become focused, the macula will also be moved further back, which in turn makes the eye more nearsighted.

Can’t we just under correct their prescription? I have heard this can help!

 

This is a question I get all the time and unfortunately, it’s an “old wives tale.” The problem with this is based on the concept of the peripheral light defocus I mentioned above. Based on the research cited,1-2 under correcting someone actually will lead to more rapid progression of nearsightedness.

How do we decide which option is right for my child?

 

Good question. This is something that we discuss on a case by case basis. With some children, we can get the sense of which method they’ll do well with. The youngest I have ever fit into contact lenses was 4 years old, but it took a lot of parental help and involvement. 

Typically, most kids are able to start off with contacts around 6-7 years old and requires a large amount of parental help for the first several months until their child has learned how to properly handle it on their own. In some cases, I prefer a soft contact lens earlier because they are daily disposables and can be discarded at the end of the day. 

In some patients, I get a sense that they would do well with a rigid lens and be able to handle it better than a soft lens. In those patients, we will often suggest ortho-keratology first. 

In patients that we get a sense they wouldn’t do well with either method of contact lenses, we will recommend atropine drops from a local compounding pharmacy.

Can we combine methods?

 

Yes, there is limited research on the efficacy of having a patient in contact lenses and atropine drops, but anecdotally, there appears to be some additional benefit. Some patients will unfortunately progress too rapidly and we’ll be limited in our options.

Are there limitations to what prescription we can start with?

 

Ortho-keratology has a prescription limit of about -5.50 for nearsightedness and about -1.50 in terms of astigmatism correction. Some prescriptions just do not work well for myopia control in rigid lenses at this time. We can attempt when we’re borderline, but we cannot guarantee a full correction. In some cases, soft lenses would be the better option or even atropine drops if we have too much astigmatism.

Citations

1. Smith M, Walline J. Controlling Myopia Progression in Children and Adolescents. Adolescent Health, Medicine and Therapeutics 2015;6:133-140. 
2. Walline J. Myopia Control: A Review. Eye & Contact Lens 2016;42:3-8