Miosis

Miosis (Greek meiosis μείωσις, downsizing ') or Stenokorie ( to gr stenos στενός closely ' κόρη and kore, pupil ') is the medical term for the uni-or bilateral constriction of the pupil. Based on an average diameter of Sehlochs they can vary in strength. A miosis caused by the contraction of the sphincter pupillae, circular or grid- like arranged trains smooth muscle in the iris of the eye or due to failure or restriction of his opponent (antagonists ), the dilator muscle of the pupil; both belong to the internal eye muscles.

The physiological miosis is mediated by parasympathetic nerve fibers and triggered as an adaptation when exposed to light and in the Nahfixation together with the accommodation and the convergence movement as so-called Naheinstellungstrias as a result of neurophysiological control loop that controls these together.

Moreover, the effect of opiates or opioids may cause miosis. Induced deliberately she is with pharmacological agents ( miotics, such as pilocarpine ) for therapeutic purposes, such as glaucoma, as well as for the differential diagnosis with the pharmacodynamic study of a tonic pupil. In contrast, mydriatics such as atropine or hyoscyamine can by a paralysis of the sphincter muscle of the pupil miosis temporarily prevent. This is when administering parasympatholytics accompanied by a Akkommodationsverlust caused by its paralyzing effect on the parasympathetic innervated portion of the ciliary muscle.

Causes a pathological miosis may damage the sympathetic supply in the Horner's syndrome ( miosis paralytic, usually unilateral ) be, as well as a bilateral reflex rigidity of the pupils at the Argyll - Robertson syndrome, usually caused by neurosyphilis. As a spastic miosis may be an irritation of the parasympathetic nervous system in Okulomotoriussystem present, most of which goes into a paralytic mydriasis and may be a transient stage of paralysis of the oculomotor nerve.

A pronounced miosis ( 2.0 mm), even in lensless ( aphakic ) people leading to some improvement in visual acuity. Because by the narrowing of the Sehlochs the depth of field is increased, similar to the screening effect when taking pictures, the operation of a pinhole camera ( camera obscura ), or a stenopaic gap.

A dilation of the pupil is referred to as mydriasis.