Vision is arguably our most important sense. Without it, our other senses allow us to paint a picture in our brains and imagine what it is happening around us. As the saying goes, seeing is believing. Unfortunately, many people around the world have impaired vision, meaning they need glasses to see. How do these glasses correct one’s vision and in case of emergency, how can one see without them?

The Principle of Vision

No glasses? No problem. Fortunately, there is a simple trick which you can use if you have misplaced your vision aid; but before I explain what the trick is and how it works, we need to understand how we can see in the first place.

How do we see?

To see, there must be light. Without light, there is no sight. In simple terms, to see an object, light from a light-source (for example, a lamp) must hit this object (for example, a book), reflect off it and head into our eyes [1]. As soon as this light reaches our eyes, it must go through the eye lens which focuses the light coming off the book onto the back of the retina to form an image that the brain then processes, to allow us to see it.

Why do people need glasses?

Ever tried taking the lens off a camera? All you’d see is one big smudge with pretty much no resolution whatsoever. This is because light goes into the camera from all different directions, with nothing to focus it into a sharp image - putting the lens back on resolves this issue. The lens in the eye does the exact same; when it is slightly damaged, the light cannot properly focus onto the retina, leading to a blurry image, hence the need for glasses. What do glasses do? They simply help the lens in the eye to sharpen up the image formed in the retina. This is why wearing glasses when you don't need them also blurs your vision!

How can we see without glasses?

As crazy as it may sound, all you need is your hand. Start by curling up your finger to make a pinhole and just put it to your eyes! If what you see through the hole is still blurred, simply adjust the size of it until your vision is in focus [2]. How does such a simple act allow for one to see so much clearer?

The Physics behind the Pinhole

Unlike a lens, a pinhole can focus any light coming from any object at any distance, since it is such a small hole – allow me to explain. A lens takes all light coming from an object and focuses it onto a point where an image of that object is formed. A pinhole blocks out a lot of the light coming from this object and only allows for some to pass through. As a result, you see a sharp, focussed image; but since a lot of the light is blocked out, the image you see is darkened. Since the need for glasses is due to damaged lenses in the eye, blocking out light from the pinhole method would mean your eyes would have to do much less work to resolve the object you are looking at! Below is an image showing the effect of a pinhole.

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Here is a fantastic video that shows you what I have explained in this article - if you are interested!

If you have any questions, leave them below and until next time, take care.

~ Mystifact

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References:
[1]: http://www.sciencemadesimple.co.uk/curriculum-blogs
[2]: https://www.sciencealert.com/watch-how-to-see-without-glasses

Please note; no copyright infringement is intended. All images used have been labelled for re-use on Google Images. If any artist or designer has any issues with any of the content used in this article, please don’t hesitate to contact me to correct the issue.

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