Mydriasis

Mydriasis (Greek μυδρίασις ) is the medical term for the uni-or bilateral dilation of the pupil. Starting from an average pupil diameter can vary. A mydriasis caused by the contraction of the dilator muscle of the pupil, radiärer or fan- like arranged trains smooth muscle in the iris of the eye, or by restriction or failure of his opponent (antagonists ), sphincter pupillae; both belong to the internal eye muscles. A maximal mydriasis is always accompanied with a round pupil, even if they vary depending on species is slot-like or oval cross in constricted state.

Physiologically normal is a two-sided Mydriasis in darkness as adaptation and when looking into the distance. A significant pupil dilation also occurs with strong sympathetic nervous system activity, such as excitement in fear, joy or emotional support.

Moreover, it can be a symptom of a disease or pathological origin are also pharmacologically induced by drugs, intoxicants, or similar plant toxins. Pathophysiologically mydriasis is present in these cases, a paralysis of the parasympathetic innervated sphincter muscle of the pupil or of its supplying nerve ( oculomotor nerve ) or a permanent contraction of the sympathetically innervated dilator muscle of the pupil basis.

Frequently mydriasis for better examination of the fundus by the ophthalmologist is medically caused by a pupil enlarging preparation is dropped into the conjunctival sac of the eye. This mydriatic effect mostly parasympatholytisch and produces a temporary paralysis of the sphincter pupillae, besides also a portion of the ciliary muscle. Due to the unobstructed light incident on the retina, the extreme sensitivity to glare associated and impaired accommodation, for example, the ability to travel on the road is no longer given for the duration of action.

In general, therefore, short-acting mydriatics are used (eg tropicamide ), while in the gift example of atropine, the effect can last for several days. In contrast, the administration of whatever mydriatic glaucoma in the present or even an acute attack of glaucoma is contraindicated. Atropine or the juice of belladonna was in the Renaissance for cosmetic reasons instilled into the eyes as mydriasis attractive worked.

A constriction of the pupil is called miosis.