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Pupillary response is a physiological response that varies the size of the pupil between 1.5 mm and 8 mm, [1] via the optic and oculomotor cranial nerve. A constriction response , [2] is the narrowing of the pupil, which may be caused by scleral buckles or drugs such as opiates/opioids or anti-hypertension medications.
Light entering the eye strikes three different photoreceptors in the retina: the familiar rods and cones used in image forming and the more newly discovered photosensitive ganglion cells. The ganglion cells give information about ambient light levels, and react sluggishly compared to the rods and cones.
The pupillary sphincter muscle and pupillary dilator muscle control the iris to adjust the size of the pupil to adjust how much light enters into the eye. The pupillary dilator muscle increases the pupillary diameter and it is arranged radially, but the pupillary sphincter muscle is responsible for the constriction of the pupil's diameter and ...
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. [citation needed] Lastly, accommodation of the lens occurs. This is an alteration in the curvature of the lens that ...
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. [5]
Light from a single point of a distant object and light from a single point of a near object being brought to a focus. The accommodation reflex (or accommodation-convergence reflex) is a reflex action of the eye, in response to focusing on a near object, then looking at a distant object (and vice versa), comprising coordinated changes in vergence, lens shape (accommodation) and pupil size.
Hutchinson's pupil is a clinical sign in which the pupil on the side of an intracranial mass lesion is dilated and unreactive to light, [1] due to compression of the oculomotor nerve on that side. The sign is named after Sir Jonathan Hutchinson. These can be due to concussion injury to the brain and is associated with subdural haemorrhage and ...
Adie's pupil is caused by damage to peripheral pathways to the pupil (parasympathetic neurons in the ciliary ganglion that cause pupillary constriction to bright light and with near vision). The pathophysiologic mechanism which produces an Argyll Robertson pupil is unclear, but is believed to be the result of bilateral damage to the pretectal ...