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The pupillary light reflex (PLR) or photopupillary reflex is a reflex that controls the diameter of the pupil, in response to the intensity of light that falls on the retinal ganglion cells of the retina in the back of the eye, thereby assisting in adaptation of vision to various levels of lightness/darkness.
The pupillary reflex results in the pupil constricting (left) and dilating (right) 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.
Pupillary accommodation reflex — a reduction of pupil size in response to an object coming close to the eye. Pupillary light reflex — a reduction of pupil size in response to light. Rectoanal inhibitory reflex - a transient relaxation of the internal anal sphincter in response to rectal distention.
A consensual response is any reflex observed on one side of the body when the other side has been stimulated.. For example, if an individual's right eye is shielded from light, while light shines into the left eye, constriction of the right pupil will still occur (the consensual response), along with the left (the direct response).
The pupillary light reflex is an autonomic reflex that controls pupil diameter to accommodate for increases in illumination as perceived by the retina. Higher light intensity causes pupil constriction, and the increase of light stimulation of one eye will cause pupillary constriction of both eyes.
The Marcus Gunn pupil is a relative afferent pupillary defect indicating a decreased pupillary response to light in the affected eye. [3] In the swinging flashlight test, a light is alternately shone into the left and right eyes. A normal response would be equal constriction of both pupils, regardless of which eye the light is directed at.
However, in any given moment of time, the eye can only sense a contrast ratio of 1,000. What enables the wider reach is that the eye adapts its definition of what is black. The eye takes approximately 20–30 minutes to fully adapt from bright sunlight to complete darkness and becomes 10,000 to 1,000,000 times more sensitive than at full daylight.
Normally, as part of the pupillary light reflex, the pupil dilates in the dark and constricts in the light to respectively improve vividity at night and to protect the retina from sunlight damage during the day. A mydriatic pupil will remain excessively large even in a bright environment. The excitation of the radial fibres of the iris which ...