Near reflex

Near reflex is a reflex action of the eye, occurring in response to an object moving closer. It involves three responses: pupillary constriction, accommodation, and convergence. The near reflex is driven by the Edinger-Westphal nucleus and is an automatic reaction, not under conscious control.

Mechanism

The near reflex is initiated when an object moves closer to the eye, triggering a signal in the retina. This signal is sent to the Edinger-Westphal nucleus, which controls the three responses involved in the near reflex.

Pupillary constriction

Pupillary constriction is the narrowing of the pupils. This occurs to increase the depth of focus of the eye by blocking the outer, unfocused light rays.

Accommodation

Accommodation is the process by which the eye changes optical power to maintain a clear image (focus) on an object as its distance varies. In this context, it refers to the thickening of the eye's lens to increase refractive power.

Convergence

Convergence is the simultaneous inward movement of both eyes toward each other, usually in an effort to maintain single binocular vision when viewing an object.

Clinical significance

Abnormalities in the near reflex can indicate a range of medical conditions. For example, Argyll Robertson pupils are pupils that constrict with accommodation but do not react to direct light. This is a sign of neurosyphilis. Another condition, Adie syndrome, is characterized by a dilated pupil that reacts slowly to light but shows normal or near-normal reaction to accommodation.

See also

• Accommodation reflex
• Pupillary response
• Oculomotor nerve

Near reflex Resources
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