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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. It may also be of unknown cause.
Tropicamide, sold under the brand name Mydriacyl among others, is a medication used to dilate the pupil and help with examination of the eye. [3] Specifically it is used to help examine the back of the eye. [4] It is applied as eye drops. [3] Effects occur within 40 minutes and last for up to a day. [3]
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.
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.
Topical atropine is used as a cycloplegic, to temporarily paralyze the accommodation reflex, and as a mydriatic, to dilate the pupils. [15] Atropine degrades slowly, typically wearing off in 7 to 14 days, so it is generally used as a therapeutic mydriatic, whereas tropicamide (a shorter-acting cholinergic antagonist) or phenylephrine (an α-adrenergic agonist) is preferred as an aid to ...
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.
In a healthy person, the biological half-life of tetryzoline is approximately 6 hours, and it is excreted in urine, chemically unchanged, at least in part. In one study, 10 people were given two drops of 0.5 mg/mL of tetryzoline eye drops (0.025–0.05 mg) at 0 hrs, 4 hrs, 8 hrs, and 12 hrs.
Light entering the eye strikes three different photoreceptors in the retina: the familiar rods and cones used in image forming and the more newly discovered photosensitive ganglion cells. The ganglion cells give information about ambient light levels, and react sluggishly compared to the rods and cones.