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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 drug.
The extraneous pupil is c. 2.5mm away from the principal pupil. In cases of true polycoria there is an intact sphincter muscle, which contracts and dilates the pupils. [5] In an eye without polycoria, the sphincter muscle is a part of the iris that functions to constrict and dilate the pupil.
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.
The size of the pupil (often measured as diameter) can be a symptom of an underlying disease. Dilation of the pupil is known as mydriasis and contraction as miosis. A human adult exhibiting voluntary control over his iris muscles, which grants him the ability to dilate and constrict his pupils on command Pupil dilated naturally to 9 mm due to ...
It also changes the shape of the lens within the eye but not the size of the pupil [5] which is carried out by the sphincter pupillae muscle and dilator pupillae. The ciliary muscle, pupillary sphincter muscle and pupillary dilator muscle sometimes are called intrinsic ocular muscles [ 6 ] or intraocular muscles .
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 ...
Refraction in the cornea causes the effective aperture (the entrance pupil) to differ slightly from the physical pupil diameter. The entrance pupil is typically about 4 mm in diameter, although it can range from 2 mm (f /8.3) in a brightly lit place to 8 mm (f /2.1) in the dark. The latter value decreases slowly with age; older people's eyes ...
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 .