Eye Pupil: Dilated vs. Contracted

Pupil: Hole in Your Eye

The pupil of your eye is the dark spot in the center of your eye. The pupil is actually a hole in your eye covered by a thin skin.

Light enters your eye through your pupil.

Pupils change size in response to light intensity.

Pupils dilate: This means the opening in the eye increases in diameter. This occurs in response to dim or no light.

Pupils contract: This means the opening in the eye decreases in diameter. This occurs in response to an increase in light intensity.

The pupils in your eyes gets smaller in bright light and larger in the dark.

eye-dilationDiscover for Yourself

Here’s how to observe the affect of light intensity on the size of your pupils.

1. Sit in a brightly lit room or sit outside in the sunshine. Caution: Never look directly at the Sun because it can permanently damage your eyes.
Close one eye and leave the other eye open. Like the child in the photo, you can use a patch over one eye.
After 2 to 3 minutes, use a mirror to observe the pupil of your open eye. Make a mental note of how large this pupil is.
4. Keep the covered eye closed as you remove any covering from this eye. With the mirror in place, open this eye and quickly look at pupil of this eye in the mirror.

Expected Results: The pupil of the eye that remained open during the investigation should be smaller than the pupil of the eye that was closed and covered.

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