Explain how the iris muscles help the eye to adapt to bright sunlight. Does the iris contract?

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In general, the role of the iris is to regulate the amount of light entering the eye by making the pupil expand and contract.  The iris is a sphincter muscle.

In bright sunlight (or bright artificial light, for that matter) the iris muscle pulls towards its center.  By doing so,...

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In general, the role of the iris is to regulate the amount of light entering the eye by making the pupil expand and contract.  The iris is a sphincter muscle.

In bright sunlight (or bright artificial light, for that matter) the iris muscle pulls towards its center.  By doing so, it reduces the size of the pupil and lets less light through.

So, yes, the muscle in the iris does contract when exposed to light and dilate when the amount of light is reduced.  It does so in order to increase or reduce the amount of light that enters the eye.

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