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Can staring at the sun permanently shrink the irises or pupils?
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scarface94 posted:
If you stare at the sun for 5 seconds, can it permanently shrink the irises and pupils of your eyes forever?
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An_252350 responded:
Your pupil changes size to control how much light enters your eye. You can observe that the pupil of your eye changes size in response to changes in lighting. You can also experiment to determine how light shining in one eye affects the size of the pupil in your other eye.
The pupil is an opening that lets light into your eye. Since most of the light entering your eye does not escape, your pupil appears black. In dim light, your pupil expands to allow more light to enter your eye.
Light detected by the retina of your eye is converted to nerve impulses that travel down the optic nerve. Some of these nerve impulses go from the optic nerve to the muscles that control the size of the pupil. More light creates more impulses, causing the muscles to close the pupil. Part of the optic nerve from one eye crosses over and couples to the muscles that control the pupil size of the other eye. That's why the pupil of one eye can change when you shine the light into your other eye.
In this experiment, the light reflecting from your eye passes through the magnifying lens twice - once on its way to the mirror and once on its way back. Therefore, the image of your eye is magnified twice by the magnifying glass.


 
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An_252350 responded:
The answer is yes. Staring at the sun is extremely dangerous and it will cause permanent damage to the eye. Will you go blind after staring at the sun one time? Well, when permanent loss of vision is under discussion, isn't even a little blindness more than enough to justify taking precautions. It is possible to stare at the sun without going completely blind, but chances are, some major damage will be done. Just like the skin, the eye is an extremely sensitive area that can be burned by the sun's ultraviolet rays.
 
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scarface94 replied to An_252350's response:
I know it changes in size depending on how dark or light it is, but that's not what I was asking. I want to know if staring at the sun once, say for 5 seconds, would permanently shring the size of the iris?


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