Pupillary reflex refers to one of the
reflex
In biology, a reflex, or reflex action, is an involuntary, unplanned sequence or action and nearly instantaneous response to a stimulus.
Reflexes are found with varying levels of complexity in organisms with a nervous system. A reflex occurs ...
es associated with
pupillary function.
These include the
pupillary light reflex and
accommodation reflex. Although the
pupillary response, in which the pupil dilates or constricts due to light is not usually called a "reflex", it is still usually considered a part of this topic. Adjustment to close-range vision is known as "the near response", while relaxation of the
ciliary muscle to view distant objects is known as the "far response".
In "the near response" there are three processes that occur to focus an image on the
retina. Convergence of the eyes, or the orientation of the visual axis of each eye towards an object in order to focus its image on each
fovea
Fovea () (Latin for "pit"; plural foveae ) is a term in anatomy. It refers to a pit or depression in a structure.
Human anatomy
* Fovea centralis of the retina
* Fovea buccalis or Dimple
* Fovea of the femoral head
*Trochlear fovea of the f ...
, is the first of the three responses. This can be observed by the cross-eyed movement of the eyes when a finger is held up in front of a face and moved towards the face. Next, constriction of the pupil occurs. Because the
lens cannot
refract light rays at the edges well, the image produced by the lens is blurry around the edges so the pupil constricts when one attempts to focus on nearby objects. Lastly, accommodation of the lens occurs. This is an alteration in the curvature of the lens that allows focus on a nearby object.
References
Reflexes
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