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[edit | edit source]
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[edit | edit source]
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[edit | edit source]
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[edit | edit source]
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[edit | edit source]
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[edit | edit source]
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