Why Does Myopia Get Worse: The Interesting Theory

Myopia (also known as nearsightedness) is a common eye condition that occurs in up to 50% of the adult population in the United States. Although it is less common in children, the number of people that have myopia is increasing. In Asian countries, myopia is more common and it is increasing even faster.

A combination of genetics, little time outdoors, a lot of time doing near work, and an increase in urbanization is probably what causes the start of myopia. But why does myopia get worse after that?

The cause for myopia progression is still unclear. There isn’t one single cause that science can attribute to this condition.

Today we are going to explore why does myopia get worse. The problem may be that normal lenses cause a peripheral overcorrection. Allow me to explain:

Myopia Explained

Let’s start off by understanding what exactly causes myopia. Light enters through the pupil, is refracted by the lens, and is focused onto the retina to send a clear image to the brain. In people with normal eyes, light from a distant object will fall perfectly on top of the retina.

For people with myopia, light focuses in front of the retina causing distant objects to appear blurry. The light falls short of the retina when it enters the eye because the eyeball has grown too long (axial elongation).

For people with hyperopia, light actually focuses behind the retina, but the eye muscles move to reshape the lens and bring the light onto the retina making vision clear. That’s why hyperopes see very well in the distance but see close objects poorly.

myopia vs hyperopia vs normal

When we correct vision with glasses or contact lenses, they help you see better because they move the image to the retina, making your eye work just like the eye of someone with perfect vision. That seems like it should solve the problem, right? Because people with perfect vision stay like that, their vision doesn’t tend to get worse and worse. So why do corrected myopes, wearing the correct glasses prescription, keep getting more myopic?

Why Does Myopia Get Worse

The answer in peripheral overcorrection (Peripheral Hyperopic Defocus Theory) says we need to pay attention to what’s occurring peripherally in the retina, instead of just trying to find the problem at the central retina (where you are viewing is being focused).

The reason why corrected myopes don’t act exactly like people with normal vision is that they don’t have the same ocular anatomy. That’s why light is focusing incorrectly in myopes in the first place. Remember, myopes have a longer eyeball.

The reason why does myopia get worse is because correcting a myope’s vision with glasses or contact lenses can make them see like a person with normal vision, but only in the central area of the retina. It ignores the fact that the eyeball is too long, so light is still focusing incorrectly in the peripheral retina in a myope. The perfect length eyeball of the person with normal vision doesn’t suffer from this.

When the eyeball elongates, it doesn’t keep a perfectly round shape like some images make it look. It’s more something like this:

why does myopia get worse

The image above is exaggerated but illustrates perfectly that a myope doesn’t have a perfect circle for an eye. Notice how the illustration points out a more oval or almost triangular shape of the myopic eye. It stretches horizontally longer.

So when a myope puts their glasses on, the focal point of the light moves back onto the retina. That’s good. The problem is this only applies to the central part of the eye and not the peripheral part.

While light focuses clearly on that elongated central retina, it is also focusing behind the retina in the periphery. Basically, the lens is too strong for the peripheral part of the eye and that’s not good.

This study shows that just 60 minutes is enough to see measurable change in the length of the eyeball when exposed to undercorrection or overcorrection:

the human visual system is capable of detecting the presence and sign of defocus and altering optical axial length to move the retina toward the image plane

When light rays fall behind the retina in the periphery, our body chemistry responds to make the eye increase its axial length. The eye is programmed to get those peripheral light rays into focus — on top of the retina (where they naturally fall in a normal eye). But the more the eye grows to try to bring those peripheral retinal images into focus, the higher the myopia prescription gets. This causes a constant loop of the eye getting more and more nearsighted.

why does myopia get worse

Possible Solution

In order to truly control myopia, we will likely need to reduce the strength (add more “plus” power) of the lens in the peripheral region. For example, -2.00 for the center region and -1.5 for the periphery. This is where multifocal contact lenses come into play.

multifocal lenses

These lenses have a ring design. This design changes the way light focuses on the retina between the central and peripheral retinal areas. This works at controlling myopia because it creates the right amount of correction for all quadrants of the retina, interrupting the feedback loop for the eye to continue lengthening.

Studies supporting this look promising. For example, this study concluded that:

Soft multifocal contact lens wear resulted in a 50% reduction in the progression of myopia and a 29% reduction in axial elongation

Conclusion

I hope this article answered the question of why does myopia get worse. Allow me to remind you the reason for myopia progression isn’t clear. This is the best of a lot of theories that exist.

Even if you’re wearing the right prescription for your eyes, that only takes into account the central part of the retina and completely ignores the rest.

Multifocal contact lenses are a promising solution for this problem. These lenses make sure the correction is right for all quadrants of the retina. Not just the center.

The best way to determine if these lenses are right for you is to speak with your eye doctor. They can assess your specific needs and find a solution that fits your unique lifestyle.

Have any questions? Leave them below in the comments and I’ll do my best to answer them. You can also contact us.

Hugo Moreira

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Evidence-Based

Every single article in Myopia Daily is fact-checked to ensure the information is high-quality, medically accurate, and meets industry standards.

I have extremely strict sourcing guidelines and only cite from the most respected sources, including recent scientific research, peer-reviewed medical journals, government agencies, scholarly articles, certified optometry websites, and up-to-date textbooks.

Factually Reviewed

My passion for promoting eye health in communities around the world fuels me to create content that is factually reviewed not only by the most up-to-date scientific research but also by everyday expertise from my personal experience with being nearsighted since I was a child.