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Mydriasis is the dilation of the pupil, usually having a non-physiological cause, [3] or sometimes a physiological pupillary response. [4] Non-physiological causes of mydriasis include disease, trauma, or the use of certain types of drugs. It may also be of unknown cause.
Nerves involved in the resizing of the pupil connect to the pretectal nucleus of the high midbrain, bypassing the lateral geniculate nucleus and the primary visual cortex. From the pretectal nucleus neurons send axons to neurons of the Edinger-Westphal nucleus whose visceromotor axons run along both the left and right oculomotor nerves .
Adie's pupil is supersensitive to ACh so a muscarinic agonist (e.g. pilocarpine) whose dose would not be able to cause pupillary constriction in a normal patient, would cause it in a patient with Adie's Syndrome. The circuitry for the pupillary constriction does not descend below the upper midbrain, henceforth impaired pupillary constriction is ...
Dilation and constriction of the pupil. Pupillary response is a physiological response that varies the size of the pupil, via the optic and oculomotor cranial nerve.. A constriction response (), [1] is the narrowing of the pupil, which may be caused by scleral buckles or drugs such as opiates/opioids or anti-hypertension medications.
All cycloplegics are also mydriatic (pupil dilating) agents and are used as such during eye examination to better visualize the retina. When cycloplegic drugs are used as a mydriatic to dilate the pupil, the pupil in the normal eye regains its function when the drugs are metabolized or carried away.
This dilation may pose a problem since a larger pupil is less efficient at focusing light (see pupil, aperture, and optical aberration for more.) Patients who have accommodative spasm may benefit from being given glasses or contacts that account for the problem or by using vision therapy techniques to regain control of the accommodative system.
Parinaud's syndrome is a cluster of abnormalities of eye movement and pupil dysfunction, characterized by: Paralysis of upwards gaze: Downward gaze is usually preserved. This vertical palsy is supranuclear , so doll's head maneuver should elevate the eyes, but eventually all upward gaze mechanisms fail.
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 ...