Today you’re going to learn about how contact lenses work for nearsightedness (also known as myopia).
If you’re reading this, you probably want to understand the mechanism behind contact lenses. They all look similar in size and structure, yet they can correct very different eye prescriptions. How is this possible?
This article will help you understand how contacts lenses work to correct myopia. And don’t worry, we’ll use simple words so that anyone can understand.
Before we can understand how contacts work, let’s start off by understanding the problem they solve: nearsightedness. Contact lenses can correct other vision problems too, like farsightedness and astigmatism. However, we will focus on nearsightedness in this article:
In a nutshell, nearsightedness is when light rays focus too early within your eye, putting the focal point of light in front of your retina instead of directly on it. Your retina is responsible for translating light into an image that your brain can read and is located in the back of your eye.
Because of this, you can see close objects sharply, but your distance vision will appear blurry. This happens because if you are nearsighted, your eyeball is longer than normal:
The most common solution for this problem is to use glasses or contact lenses. They will move the focal point further back onto the retina creating a clear image.
But how do contact lenses make such a big difference in your vision if they’re so tiny and look the same even for completely different eye prescriptions? How do contact lenses work for nearsightedness? Here’s the deal:
How Contact Lenses Correct Nearsightedness
All contact lenses don’t have the same exact shape. Even though to the naked eye, contact lenses look like the same thin flimsy material that can magically bend lights, they have some microscopic nuances that are actually enough to correct vision. Because they sit so close to the eye, these small changes are enough.
A contact lens is a thin, transparent plastic disk you wear in your eyes. They improve your vision by bending light so that it focuses on the retina. Glasses work the same way.
Contact lenses used to correct nearsightedness are concave. A concave lens means it is thicker on the edges and thinner in the center. This difference in thickness is not noticeable to the naked eye. This is why all contact lenses look similar.
For farsightedness, it’s the opposite. Corrective lenses are convex, which means the thickest part of the lens is in the middle. This bend light towards the center.
So, now we know that the corrective power of contact lenses comes from the fact that they are thinner in the middle than in the borders. But this doesn’t apply to the whole surface of the lens. Here’s the deal:
Because contact lenses sit right on your eye, only the middle part of the lens contains corrective power. This corrective zone is generally around the same size as your pupils in low-light conditions (7 to 9 millimeters). The rest of the contact lens is useful to help it fit your eye and stay in place but does not affect vision.
This is different from glasses, in which the whole surface of the lens has corrective power. This is because glasses are not as close to your eyes as contact lenses. Now:
To correct myopia, concave lenses (also called “minus” lenses) spread the light away from the center and move the focal point of the light forward so that it reaches the retina, creating a clear image.
The Takeaway on Contact Lenses for Myopia
In this article, we looked at how something so small as contacts makes such a big difference in your vision.
To correct nearsightedness, contact lenses are thinner at the center than at the edges. This difference in thickness is only present in the middle of the lens. The peripheral part of contact lenses doesn’t affect vision.
If you still have any questions on what do contact lenses do, don’t hesitate to leave them in the comments below! We will get back to you as soon as possible.
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