Why can you look through a small O formed by forefinger and thumb as a shortsighted person and see sharply?
In: Biology
If you think about how the light from a single point goes it makes sense. The problem is that the light from a point spreads out and hits your entire pupil. The job of the lens in the eye is to curve the light from the edges of the pupil to make sure they hit the retina in exactly the same spot. But for people who are short sighted they can not focus their lens so that light that comes in almost parallel hits the same spot on the retina no matter where in the pupil it goes through. It all hits slightly different spots making the image fuzzy. By looking through a smaller hole you block out the light from the point which hits the edge of your pupil. So the light now hits the retina in a smaller spot and therefore makes the image much more clear. However there is less light hitting your eye so the image does appear darker.
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