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A New Look at Myopia

Posted by Ilena Di Toro | Posted on January 23, 2024

Since the development of spectacles, myopia isn’t considered a big deal in terms of vision conditions. After all, how many medical conditions are as easy to treat as myopia? A person just needs some corrective lenses and he or she is good to go. Hearing loss isn’t as easy treat as myopia. Just ask someone who has hearing aid about the challenges he or she faced regarding hearing aid adjustments.

Now researchers are taking myopia seriously, especially since it has twice the global presence of obesity. In fact, 40 percent of the U.S. population has myopia and that percentages is upwards of 90 percent in Asian countries. In addition, it is associated with retinal detachment, myopic maculopathy, or glaucoma.

Interestingly enough, education is one of the biggest risk factors for myopia. One of the biggest connections between myopia and education is that those who continue their education to university and beyond are more likely to spend time indoor doing near work. Yet, as great as it is for a person to continue his or her education, one study done at the State University of New York, College of Optometry, found that reading increases the risk of developing myopia.

The research was published in the Journal of Vision and scientists were able to show the images form by the eye while reading lacks diversity of contrasts, visual motion and visual change needed to activate major visual pathways that signal light stimuli. These are known as the ON pathways since they are responsive to light that is on. The study compared visual inputs and visuomotor activities that have high and low risk of myopia progression, namely reading (high risk) and walking (low risk).

The results of the study showed that many factors made reading less likely to activate the ON pathways than walking. Based on these findings, researchers propose that the ON pathway needs to activated to properly adjust eye growth. They found that reading for a long period of time reduces the activation of the ON pathway and it makes the eye grow beyond the focus plane and blurring vision at a far distance.

Yet, there are treatments that can slow the progression of myopia. One of which is atropine eyedrops. A study done by the Singapore National Eye Center in 1999 on children between the ages of 6 and 12 years-old tested four different does of atropine and they were 0.01, 0.1, 0.5, and 1 percent, respectively. Researchers found that when they administered the 1 percent dose they were able to slow the progression of myopia by 78 percent and they were able to slow progression with the very low dose, 0.01 percent by 50 to 60 percent.

As great as this sounds, atropine eyedrops aren’t used outside of Asia, except for the treatment of amblyopia for children in the U.S. There are also side-effects associated with atropine, such as light sensitivity and blurry near vision when it is used at the 1 percent dose. Researchers are looking to do an atropine trial in Europe and get follow up data from Taiwan, where atropine has been used on children for 20 years.

Pharmaceuticals aren’t the only way to reverse myopia. Specialized lenses can be utilized, as well. One type are the peripheral defocus contact lenses. Treatment using these lenses is based on the theory that axial eye growth is influenced by blurred vision in the peripheral retina. While introducing a hyperopic blur accelerates axial growth, inducing a myopic blur in the retina’s periphery will slow it down by as much as 30 to 50 percent. With peripheral defocus contact lenses, the center part of the lens corrects nearsightedness and the progressive rings around the lens corrects peripheral hyperopia.

Another type of specialized lenses are orthokeratology, also known as Ortho-K. They are rigid contact lenses that are worn overnight to reshape the cornea. The effect on the eye is similar to the peripheral defocus contact lenses, in that Ortho-K also shapes the cornea to change the off-axis defocus on the retina, so that axial growth is slowed and the hyperopic blur in the periphery is reduced. Several studies have shown that long term use of Ortho-K lenses may reduce the progression of myopia by as much as 43 percent. The downsides of Ortho-K lenses include the risk of infection and the cornea goes back to the its previous shape a week after the lenses are removed. Still, lenses are having an impact on axial length.

So, myopia isn’t just the inconvenience that it was previously thought. While corrective lenses do a good job in correcting vision, myopia remains and diseases such as retinal detachment, myopic maculopathy, or glaucoma can develop. All the more reason to reverse myopia.

Sources:
https://www.aao.org/eyenet/article/myopia-research-from-margins-to-mainstream

https://www.sunyopt.edu/news/reading-and-visual-health/

https://www.mykidsvision.org/knowledge-centre/ortho-k-for-myopia-control

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