Dilator pupillae

Dilator Pupillae

The Dilator Pupillae is a muscle located in the eye, specifically within the iris. It is responsible for controlling the size of the pupil, allowing it to dilate (expand) in low light conditions. This action increases the amount of light that can enter the eye, enhancing vision in darker environments. The dilator pupillae works in opposition to the sphincter pupillae, which constricts the pupil in bright light to reduce the amount of light entering the eye and prevent damage to the retina.

Anatomy

The dilator pupillae muscle is a thin, radial muscle that extends across the iris, from the sclera to the edge of the pupil. It is innervated by the sympathetic nervous system, which activates the muscle in response to low light conditions or other stimuli, such as the "fight or flight" response. The sympathetic stimulation causes the muscle fibers to contract, pulling the iris outward and enlarging the pupil.

Function

The primary function of the dilator pupillae is to control the diameter of the pupil, thereby regulating the amount of light that enters the eye. In dim lighting, the sympathetic nervous system stimulates the dilator pupillae to contract, dilating the pupil and allowing more light to reach the retina. This mechanism is crucial for optimizing vision in varying light conditions.

Clinical Significance

Abnormalities in the function of the dilator pupillae can lead to issues with pupil dilation and light regulation, affecting vision. Conditions such as Anisocoria (unequal pupil sizes), Horner's syndrome (a syndrome that affects the eyes and face), and Adie's pupil (a condition where the pupil is dilated and reacts slowly to light) can indicate problems with the sympathetic innervation or the muscle itself. Treatment and management of these conditions depend on the underlying cause.

See Also

• Iris (anatomy)
• Pupil
• Sphincter pupillae
• Sympathetic nervous system
• Eye anatomy