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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 responses can reflect activation of the brain allocated to cognitive tasks. Greater pupil dilation is associated with increased processing in the brain. [45] Vacchiano and colleagues (1968) found that pupillary responses were associated with visual exposure to words with high, neutral or low value.
Many automated pupilometers can also function as a type of pupil response monitor by measuring pupil dilation in response to a visual stimulus.. In ophthalmology, a pupillary response to light is differentiated from a pupillary response to focus (i.e. pupils may constrict on near focus, as with the Argyll Robertson pupil) in the diagnosis of tertiary syphilis.
[clarification needed] The fixation sites are located in the midperiphery of the iris, which is immobile during pupillary movement. The original biconvex lens design was modified into a convex-concave design, [ 1 ] and manufactured as Artisan/Verisyse lens and later the foldable model (Artiflex), a three-piece lens with silicone optic and PMMA ...
The pupil constricts when the iris sphincter muscle is stimulated and contracts In humans, it functions to constrict the pupil in bright light ( pupillary light reflex ) or during accommodation . [ citation needed ] In lower animals, the muscle cells themselves are photosensitive causing iris action without brain input.
It is performed by shining a light in the person's eyes and observing where the light reflects off the corneas. In a person with normal ocular alignment the light reflex lies slightly nasal from the center of the cornea (approximately 11 prism diopters—or 0.5mm from the pupillary axis), as a result of the cornea acting as a temporally-turned ...
Cones work at high light levels (during the day but also during driving at night in the headlamp spotlight). Rods take over at twilight and night. The y-axis has logarithmic scaling. A minor mechanism of adaptation is the pupillary light reflex, adjusting the amount of light that reaches the retina very quickly by about a factor of ten. Since ...