The Myopia Epidemic

The phrase “short-sighted” can be used in a variety of different contexts. For example, “Purchasing that bright purple couch before seeing the finished house was a rather short-sighted decision”, or “My grandpa is so short-sighted that I can stand a foot away and he’ll think I’m my sister. But I’m actually John.”

Myopia, the medical term for short-sightedness, is a type of refractive error of the eye that involves the focusing point of the eye falling in front of the retina, meaning a blurry image ends up hitting the actual retina. In other words, the length of the eyeball is too long for the focusing power of the eye. Myopia is typically addressed using minus powered spectacle or contact lens, which alters the path of light entering the eye such that it focuses properly onto the retina to form a clear image to the brain. Without optical correction, a myopic person would have difficulty with seeing distant objects clearly; the amount of blur in the distance would correspond to his/her degree of myopia.

 
The Myopia Epidemic
The prevalence of myopia in the United States currently hovers around 42%, having doubled in numbers over the last 30 years in what has been termed a worldwide myopia epidemic. In California specifically, a little over 3.5 million people are short-sighted. A recent study found that 4% of adults in the US are considered highly myopic, defined in this study as a script of -6.00D or higher. This degree of short-sightedness was chosen because without spectacles or contact lenses, a -6.00 myope would be classed as legally blind as per the World Health Organization’s definition.

Uncorrected -6.00 myopia also falls outside the vision requirements for driving in most countries. Prevalence rates of short-sightedness are even higher in southeast Asian countries; in Seoul, 96.5% of 19-year-old males were found to have some degree of myopia, one of the highest published myopia rates in the world. The global prevalence is expected to rise in the coming years, reaching an estimated 50% of the world’s population by 2050. One of the reasons for this myopia boom is thought to be an earlier onset of short-sightedness in children, known as childhood or school-aged myopia. It is known that the earlier myopia begins, the more aggressively it tends to progress. The presence and development of short-sightedness is thought to have both genetic and environmental factors.

The structural differences in a myopic eye compared to an eye with no refractive error (known as an emmetropic eye) unfortunately lend this eyeball a few extra risks when it comes to sight-threatening ocular pathology. These risks have no cut-off and continue to increase with increasing severity of myopia.

  • Cataract. An opacity of the usually transparent lens inside the eye, even just -1.00D of myopia doubles the risk of developing cataract.
  • Glaucoma. Involving damage to the optic nerve and the back of the eye and subsequent irreversible peripheral vision loss, myopes have been found to have a two- to three-fold increased risk of glaucoma compared to an emmetropic person.
  • Retinal detachment. In an elongated myopic eyeball, the retina is stretched more thinly over the greater surface area, making it more prone to tearing or detaching from the wall of the eyeball. A -1.00D myope has a three-times greater risk and a -3.00D myope a nine-times greater risk of a retinal detachment.
  • Myopic maculopathy. Now becoming one of the leading causes of irreversible blindness in Asian populations, myopic maculopathy is damage to the stretched-out retina specifically at the macula, which processes central vision. -3.00D myopia carries nine times the risk of vision loss from myopic maculopathy.

 
Considering the statistics we discussed at the outset, it is not unlikely that you have some degree of short-sightedness (whether of the mental or ocular variety ?). Current research is being devoted to the concept of myopia control, aimed at slowing the progression of short-sightedness in children to minimize the risk of future blinding complications. Unfortunately, this research doesn’t extend past the mid to late teens but for suitably aged candidates, the results are promising.

Interventions including atropine eyedrops, ortho-keratology, soft multifocal contact lenses, bifocal and multifocal spectacle lenses have all been shown to provide varying degrees of reduction of the rate of myopic progression.

  • Atropine. The use of atropine eye drops has been studied in various concentrations. 0.01% atropine was found to be the most effective in minimizing the potential side effects such as glare sensitivity and near vision blur, while still providing a reasonable amount of myopia control. The actual explanation behind atropine slowing myopia progression is not yet fully understood.
  • Ortho-keratology. Ortho-k involves wearing a specially shaped hard contact lens in the eye overnight. The idea is that the shape of the hard lens will change the focus of light specifically in the peripheral retina by reshaping the cornea (the front surface of the eye) and this, in turn, will signal the eye to slow its growth. As an added bonus, with successful ortho-k treatment, not only will the rate of myopia progression be significantly reduced but the child also can be spectacle- and contact lens- free during the day.
  • Soft multifocal contact lenses. The premise behind the use of multifocal contacts is similar to that for ortho-k – inducing a different focus on the retinal periphery to encourage the eyeball to stop growing so darn long.
  • Bifocal and multifocal spectacles. These types of spectacle lenses contain the child’s distance script at the top of the lens and a stronger reading script at the bottom. It is hypothesized that the progression of short-sightedness is slowed using this treatment due to reducing any strain the eye experiences while focusing at something near because the reading portion of spectacle lenses gives the eyes a boost. The degree of myopia control from such lenses, while found to be statistically significant, is not considered clinically significant. Much better results are found with the other treatments.

 
While a kid can’t always (or ever) control their genes or environment, it is important to know there are options available for slowing the progression of myopia in the effort to reduce the risk of myopia-related eye diseases. It is also important to at least have a look at the new house before buying that bright purple couch.

 
References
Myopia – Growing Prevalence. https://www.brienholdenvision.org/myopia-prevalence.html
Nearly 10 million adults found to be severely nearsighted in the United States. https://www.aao.org/newsroom/news-releases/detail/ten-million-severely-nearsighted-united-states
Myopia prevalence rates by state. http://www.visionproblemsus.org/refractive-error/myopia/myopia-map.html
Prevalence of myopia and its association with body stature and educational level in 19-year-old male conscripts in Seoul, South Korea. http://iovs.arvojournals.org/article.aspx?articleid=2166142
Taking action to manage myopia. http://www.mivision.com.au/taking-action-to-manage-myopia/
The relationship between glaucoma and myopia. http://www.aaojournal.org/article/S0161-6420(99)90416-5/abstract
Myopic maculopathy. https://www.snec.com.sg/eye-conditions-and-treatments/common-eye-conditions-and-procedures/Pages/myopic-maculopathy.aspx
Efficacy comparison of 16 interventions for myopia control in children. http://www.aaojournal.org/article/S0161-6420(15)01356-1/fulltext
Multifocal contact lens effective at treating myopia in kids. https://www.aoa.org/news/clinical-eye-care/multifocal-contact-lens-effective-at-treating-myopia-in-kids
Slowing myopia in children. https://www.reviewofoptometry.com/article/slowing-myopia-progression-in-children

 

 


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