Eli5 Looking thrue magnifying glass, telescope or microscope does not hurt. Looking thrue glasses with wrong lenses hurts. Why?

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Eli5 Looking thrue magnifying glass, telescope or microscope does not hurt. Looking thrue glasses with wrong lenses hurts. Why?

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The glasses are not magnifying, they are changing the way light is focused into the eye. People who need glasses don’t see things as too small, they see them as blurry.

Looking through glasses when you don’t need them hurts because your eyes are trying to focus on light that is modified to work with eyes that have a different lens shape than yours. This means the muscles in your eye are trying to pull your lens into a different shape, something that strains them as even working their hardest they will fail.

Magnifying glass, telescope, and microscopes just magnify an image (enlarge it), and assumes your eye / cornea are already the correct shape to process the image properly.

But prescription glasses bend the light in such a way that when it hits your misshapen cornea / eye / whatever (I’m not an eye doctor), the 2 kind of ‘cancel’ out and what you see is a clear image. When someone who wears glasses takes them off, its not just that things look far away and need to be bigger to see, but that they are *blurry*. My understanding is that the prescription glasses kind of bend the light in the opposite way that your eye is bending the light, to make things appear clear and in-focus. Hope this helps.

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Edit: Sorry, so to address your question, if you wear a prescription that is wrong for your eyes, the light is being bent in a way that is not compatible with your eyes, so it does not help you and makes things look blurry, because it is not “canceling” like it would if you actually needed thatt prescription.

Your eyes are a muscle. If light isn’t hitting it correctly, it will strain to aim the light where it should be. So it’s getting a workout trying to focus and the harder it works the more you feel it. Microscopes, telescopes, etc all allow you to focus the image you’re seeing through it. So you adjust it until the image is clear to your eyes thereby preventing them from straining and causing you discomfort.

When using the wrong glasses, the image is almost in focus, so your eyes strain to bring it into focus. An out of focus magnifying glass or telescope is so far from focus that your eyes don’t try.