What is Myopia?
Myopia is the refractive error of the eye that results in blurred distance vision. It is the result of the length of the eye (axial length) being longer than it should be, the power of the internal lens of the eye (crystalline lens), the power of the cornea (clear part of the front of the eye), or a combination of all of them. In a myopic eye, the point in which the distance image if focused falls short of the retina, resulting in a blurred image reaching the retina. Myopia is sometimes referred to as “near sightedness” because when an object is brought closer to the eye, there is a specific distance (depending on the amount of myopia) in which that object will be clearly seen. This is because the near object “pushes” the focus point to the retina, and the vision is clear (near sight) without any effort from the focusing muscles.
What Causes Myopia Progression?
A child’s risk of developing myopia is influenced by genetics. If one or both parents are myopic, the child’s risk of becoming myopic (nearsighted) is three times and six times more likely, respectively, to become myopic as well.
Environment also plays a role in a child developing myopia. A child who spends a significant amount of time working at a near distance (phone, tablet, reading, computer, etc.) and a limited amount of time outdoors is at a three times greater risk of developing myopia when compared to a child with limited near work and higher outdoor time. Outdoor light has a different spectral composition than indoor light, and is up to 100 times greater than indoor illumination. It is theorized that both of these may play a role in developing myopia. However, while it has been determined that outdoor time increases risk of developing myopia, it is unclear if outdoor time helps slow myopia progression.
As children grow, their eyes can become longer and larger, in fact, retinal blur influences eye growth. This is a term called emmetropization. Ideally at birth, the eye will start hyperopic (far sighted), with a prescription of about +1.25D by the time a child is 6 years old. As the child grows the eye elongates and the amount of hyperopia decreases. If everything works out exactly right, when the child has finished growing (late teens to early twenties) the prescription will end up at zero prescription, called emmetropia. If the eye starts at a lower hyperopic prescription, or even myopic, as the child grows, the eye’s axial length will eventually become longer than it should be and become myopic. It’s interesting to note that the central retina (fovea) is not the key area in determining eye length (axial length) growth, rather the peripheral retina is responsible for the stimulus for the eye to elongate. What that means is that with extensive time spent looking at near objects, the peripheral retina is constantly receives a near object target. The eye “monitors” its status and it “knows” if it defocuses continually (extensive near focus) it can alter its axial length by growing to reach the refractive error necessary to match the target it is exposed to.
Expected Refractive Error Based on Age
· Age 6 Refractive Error +0.75D or less
· Age 7 +0.50D or less
· Age 8 +0.50D or less
· Age 9 +0.25D or less
· Age 10 +0.25D or less
· Age 11 +0.00D or less
What is Myopia Management?
Myopia Management is a term used to describe various treatment methods used to slow down the progressive loss of distance vision. These treatment methods can be either creating optical defocus or by biochemical influence. These methods include Corneal Refractive Therapy (CRT) which uses specially designed RGP contact lenses to gently reshape the cornea while sleeping, to provide clear vision during waking hours without glasses or contact lenses. Multifocal Soft Contact lenses, which are used to create peripheral defocus, which has been shown to slow myopia progression. Low Dose Atropine (0.01%) drops which have been one of the more effective ways to slow progression. And Executive Bifocal Spectacle Lenses, which can also have a benefit in slowing myopia progression for those patients who aren’t candidates for CRT or multifocal contact lenses, or are not interested in using Atropine drops.
Why is Myopia Management Important?
Myopia is becoming an epidemic throughout the world. There is no “safe” level of myopia. The prevalence of myopia in the United States is estimated to between 33-42% of the population (almost 100 million Americans), which has doubled since 1972. In China the prevalence is higher, estimated to be 65% of the population and in other eastern Asian countries the prevalence is even greater than that. In Taiwan, 81% of the population is myopic, and in South Korea, 97% of their population is myopic. The World Health Organization has estimated that by 2050, 50% of the world’s population will by myopic, and of those, 10% (1 billion people) will have severe myopia; defined as greater than or equal to -5.00D of myopia.
Besides the progressive loss of clear distance vision there are health risks that can result from increased levels of myopia. The higher the amount of myopia the greater the risk of developing cataracts, glaucoma, posterior vitreous detachment, myopic macular degeneration, posterior staphyloma and retinal tears and detachments, to mention a few.
· The risk of glaucoma is 14.4 times higher for a person with -6.00D of myopia when compared to a person with no myopia (emmetropia).
· The risk of retinal detachment is 7.8 times higher for a person with -8.00D of myopia when compared to a person with emmetropia
· The risk of cataracts are 3.3 times higher for a person with -6.00 D of myopia compared to a person with emmetropia.
· The risk of myopic macular degeneration is an alarming 40 times greater risk for a person over -5.00D of myopia compared to a person with emmetropia.
As more and more studies show the efficacy and safety of myopia management treatments, controlling myopia has come to be viewed as more of a necessity than an elective luxury by eye care professionals, educators and parents.
Why Haven’t I Heard of Myopia Management Before?
In many instances, eye care has become a version of “fast-food” commercial optical retail stores, whose main concern is how many “customers” can be seen in the shortest amount of time possible and how many glasses can be sold. As the results of the studies looking at the effectiveness of Myopia Management are becoming more readily available, it is possible that many of these doctors haven’t had an opportunity to learn about these new treatment options, or perhaps their practice organization doesn’t allow for this type of treatment option to be utilized. The evidence is very clear that myopia progression can be slowed, and with the potential health risks of severe myopia, we feel that treating myopia early is very important.
Benefits of Myopia Management Treatments
Unfortunately, myopia cannot be “cured” or reversed. However, with current Myopia Management Treatment methods, the risk of myopia progression can be reduced, and the rate of myopia progression slowed. The benefit of initiating Myopia Management is reducing the amount of myopia a child would have developed if nothing were done. The World Health Organization has indicated that a myopic prescription of -5.00D or higher is considered severe myopia. Severe myopic eyes are at a dramatically greater risk for myopia related ocular diseases. If by employing the various Myopic Management Treatment methods, a child’s myopia can be kept below -5.00D, the risk of these related ocular diseases can be dramatically reduced. Treatment should continued as long as myopia progression occurs, and can be stopped once myopia is stable for 2 years or more.
Candidates for Myopia Management Treatment
It is recommended that Myopia Management Treatment methods be initiated as soon as a child has developed -0.50D of myopia. The different treatment options each have different criteria that make a child a better candidate for one treatment option or another. These differences will be discussed during a Myopia Management evaluation.
What are Risk Factors for the Development of Myopia?
The myopic risk profile can be helpful to determine if a child is at a greater risk for developing myopia.
- Age – Myopia develops during early to middle childhood ages and progresses before stabilizing (usually) in late adolescence. Myopia also seems to progress faster at a younger age.
- Refractive Error – If a child’s refractive error (prescription) is lower than would be expected for their age.
- Ethnicity – Highest prevalence of myopia is in children of eastern and southern Asian descent. 65% of the population in China, 81% in Taiwan and 97% in South Korea. Incidence of myopia is lower in the rest of the world. 35% of the population of Europe is myopic and only 6% of the population of Ethiopia and Tanzania.
- Parental Myopia – If one parent is myopic, the child is at a 3 times greater risk of developing myopia. If two parents are myopic, the child is at a 6 times greater risk of developing myopia.
- Time Spent Outdoors – The highest associated environmental risk is low outdoor time; less than 1.5 hours per day outside. Moderate risk with 1.5-2.5 hours per day, and lowest risk with more than 2.5 hours per day.
- Time Spent with Near Work – The highest associated risk long hours spent with close work (smart phones, tablets, reading, computer, homework, etc) of longer than 2.5 hours per day. Moderate risk is 1.5-2.5 hours per day, and lowest risk with less than 1.5 hours per day.
If a child has 5 or 6 of these risk factors, there is a high risk of developing myopia.
If a child has 3 or 4 of these risk factors, there is a medium risk of developing myopia.
If a child has 0 to 2 of these risk factors, there is a low risk of developing myopia.
What are Risk Factors for Myopic Progression?
If a child has developed myopia, these risk factors can help determine the risk of myopia progression.
· Age – Myopia progresses faster at younger ages.
· Age 7 Average Annual Progression -0.89D
· Age 8 -0.80D
· Age 9 -0.71D
· Age 10 -0.63D
· Age 11 -0.54D
· Age 12 -0.45D
· Age 13 -0.37D
· Age 14 -0.28D
· Age 15 -0.19D
· Age 16 -0.11D
· Ethnicity – Myopia Progression rate is faster in children of Asian descent.
· Parental Myopia – Myopia Progression is faster with family history.
0 parent Average Annual Progression -0.36D
1 parent -0.64D
2 parent -0.66D
· Time Outdoors – There is not a lot of strong evidence to show that outdoor time helps to slow myopia progression
· Time with Near Work – There is a lot of strong evidence to show that reducing the amount of near work will help slow myopia progression.
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