Myopia (nearsightedness) is the ability to see well without glasses correction during near activities but inability to see well for distance activities. Myopia is created primarily by “axial elongation”, meaning an eyeball that grows longer than it otherwise should. Myopia is technically considered an optical condition of the eye, not a medial condition, and therefore its treatment is not covered by medical insurances. However, there are socio-economic implications. For example, myopic children without easy or cost effective access to eye care providers may perform at levels below their non-myopic peers in school due to the inability to see the board well. For adults, wearing glasses at work may pose a safety concern. Contact lenses or refractive surgery such as LASIK may not always be medically or financially possible. In rare cases, the physical elongation that occur to the eye in the progression of high myopia may make a person more at risk for secondary medial issues, such as retinal detachments, which can be sight threatening.
Although myopia for most individuals is more of an inconvenience than a sight threatening condition, for the above mentioned reasons there has been recent research to determine what causes myopia and how to limit its progression.
Cause of Myopia
Myopia is a classic example within research of a case between nature versus nurture. Meaning, is it genetic or is it caused by a person’s environment? The argument for it being genetic comes from studies that show children born to parents who are both myopic are twice as likely to be myopic than those born to non-myopic parents.
The argument in favor of environment causing myopia comes from studies that show those who spend the most time reading and other near activities are more likely to be nearsighted than those who spend the fewest hours reading. For example, a study from China found the prevalence of myopia in the most rural areas with the lowest literacy rates to be 1% compared to 38% in more industrialized parts such as Hong Kong where the school year, school hours, and study times are longer. Near point activities such as reading cause a measurable increase in “axial elongation” (the length of the eye). Although discontinuing reading causes the eye to quickly return to is normal shape, it is believed that this axial elongation repeated many times over the course of years causes a permanent elongation to occur.
This apparent environmental correlation poses a secondary question. Are the studies that show a genetic correlation actually discovering that highly educated parents encourage more reading behaviors in their children? Are those myopic parents creating myopic children not through genes, but through encouraging reading? Although still debated, most researches currently believe that myopia is a combination of genetic and environmental factors.
Controlling the progression of myopia
Obviously we cannot control our genes or the amount of homework our children are given, but there are several methods proven to slow myopia’s progression in an individual over the course of years. None of the methods stop myopia progression and certainly none reverse myopia. Each of the methods below, however, does slow its progression to varying small degrees. As a result, it is important to discuss with your doctor whether the commitment of long term therapy is worth the difference in outcome. With or without treatment, your myopic child will still be myopic. It becomes a question of can we make him or her less myopic than they would otherwise be 5 years down the road.
1. Outdoor time
Several studies have pointed to time spent outdoors as being correlated with lower rates of myopia progression. Research from Taiwan showed the prevalence of myopia in 7-11 year old children exposed to an additional 80 minutes of sunlight daily for 2 years was half that found in a control group of children without the intentional extra 80 minutes of daily sunlight exposure. Of the kids in either group who were myopic at the end of the study, the total amount of myopia in the “extra sunlight” group was about 1.00 diopter less than the control group. This would be a noticeable amount to a child in a classroom.
Although the mechanism is not yet understood, it is believed dopamine released during sunlight exposure reduces axial elongation over the long term. Additionally, more leisure time spent outdoors means less time on the phone or tablet, which we know from earlier causes a lengthening of the eye. So although we cannot control the amount of homework our children have, we can control the types of activities they are doing when homework is complete. Studies show outdoor activities may be the type of activities we want to encourage in order to inhibit the progression of myopia. Cost: Free.
Atropine is similar to the dilating drops you have likely received during an eye exam. The goal of atropine is to inhibit the ability of the ciliary muscles (focusing muscles) in the eye from flexing during near activities. Why might this be beneficial? Because when we paralyze the focusing muscle inside the eye the eye cannot elongate during reading activities. Since the focusing muscle is paralyzed, reading glasses may be needed for near activities to do the work that the focusing muscle no longer can. However, a very low dose is used and most children in the study were able to still read without the use of reading glasses.
A 2-year study of Atropine drops used nightly showed children had their myopia progress 0.28 diopters over 2 years as compared to 1.20 diopters for children on a placebo. Both groups of children still need glasses, but the prescription was about 1 diopter less at the study’s conclusion for those who used the drops nightly. 1.00 diopter less myopia would make a noticeable difference for someone with a relatively mild to moderate amount of myopia. Cost: About $30 per month.
3. Bifocal glasses
Although bifocals are typically thought of as being for those over the age of 40, they have been researched in myopia progression treatment. Similar to atropine, the bifocal inhibits the ciliary muscle from flexing during near activities. Whereas Atropine does it thorough the use of an eyedrop, bifocals do it optically. Most studies show that the use of a bifocal does not slow myopia progression enough for it to be a worthwhile option. Although it is shown to slow the progression, the degree of slowing was less than 0.50 diopters over 30 months. Likely not enough for a quality of life difference and making this the least effective of the myopia control options. Cost: About $50-200 more per year than a non-bifocal pair of glasses, depending on type of bifocal selected.
CRT is an acronym for Corneal Refractive Therapy. CRT uses a rigid contact lens to gently reshape the cornea (front surface of the eye) while the patient sleeps. The reshaping effect is temporary after the lens is removed in the morning, but lasts long enough that the patient does not need glasses or contact lens wear during the daytime. Typically used in children who are not yet old enough for LASIK or adults who want a nonsurgical alternative to wearing glasses, recent research has shown that CRT has the added benefit of slowing overall myopia progression by slowing axial elongation.
A study of 138 children showed that CRT overnight lenses slowed myopia progression by 0.50D per year. Cost: About $1,400 for the first year, and about $400 per year thereafter for new contact lenses and professional refitting fees.
There is nothing available to halt or reverse the natural progression of myopia. As discussed above, the best options available to slow its progress will likely make no noticeable difference for someone destined to become highly myopic. However, for children destined for low amounts of myopia, using one of the above active therapies may mean the difference between needing glasses only part time instead of full-time.
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