The sphincter pupillae muscle controls decreasing pupil size in response to brighter light levels. This action protects the eye from potential damage. The process is involuntary and controlled by the autonomic nervous system.
The pupil size in our eyes is controlled by two muscles: the sphincter pupillae and the dilator pupillae. When we are exposed to brighter light levels, the sphincter pupillae muscle contracts, which causes the pupil to decrease in size. This acts as a protective mechanism to prevent too much light from entering the eye and possibly causing damage.
The functioning of these muscles are involuntary and controlled by the autonomic nervous system. In contrast, in lower light levels, the dilator pupillae muscle would contract to increase pupil size and allow more light in for improved vision.
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