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A mydriatic pupil will remain excessively large even in a bright environment. The excitation of the radial fibres of the iris which increases the pupillary aperture is referred to as a mydriasis. More generally, mydriasis also refers to the natural dilation of pupils, for instance in low light conditions or under sympathetic stimulation.
Dilation and constriction of the pupil 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 ( miosis ), [ 2 ] is the narrowing of the pupil, which may be caused by scleral buckles or drugs such as opiates / opioids or ...
The extent of vasoconstriction may be slight or severe depending on the substance or circumstance. Many vasoconstrictors also cause pupil dilation. Medications that cause vasoconstriction include: antihistamines, decongestants, and stimulants. Severe vasoconstriction may result in symptoms of intermittent claudication. [1]
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 .
Side effects may include allergic reactions, eye pain, and dilated pupils. [2] [4] [3] It is unclear if use in pregnancy is safe. [1] Nephazoline works by resulting in constriction of blood vessels thus decreasing redness while pheniramine works by blocking the effects of histamine to stop itching. [1]
Antihistamines, specifically H1-antihistamines, are medicines which provide relief for allergic symptoms such as runny nose, sneezing, itching, and watery eyes from seasonal allergies . They are usually the first line of medications prescribed by a general practitioner, or a pharmacist for allergies in a community pharmacy.
Clemastine is an antihistamine with anticholinergic and sedative effects. Antihistamines competitively bind to histamine receptor sites, thus reducing the neurotransmitter's effects. [9] Effects of histamine (which are countered by antihistamines) include: Increased capillary permeability; Increased capillary dilatation; Edema (i.e., swelling ...
Antihistamines are drugs which treat allergic rhinitis, common cold, influenza, and other allergies. [1] Typically, people take antihistamines as an inexpensive, generic (not patented) drug that can be bought without a prescription and provides relief from nasal congestion, sneezing, or hives caused by pollen, dust mites, or animal allergy with few side effects. [1]