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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]
[1] [5] As an eye drop it is used to manage angle closure glaucoma until surgery can be performed, ocular hypertension, primary open angle glaucoma, and to constrict the pupil after dilation. [1] [6] [7] However, due to its side effects, it is no longer typically used for long-term management. [8]
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.
When light is shone into right eye, right pupil constricts. Direct reflex of the right pupil is unaffected, The right afferent limb, right CN II, and the right efferent limb, right CN III, are both intact. The left consensual reflex is lost. When the right eye is stimulated by light, left pupil does not constrict consensually.
Hydroxyamphetamine is used in eye drops to dilate the pupil (a process called mydriasis) so that the back of the eye can be examined. This is a diagnostic test for Horner's syndrome . Patients with Horner's syndrome exhibit anisocoria brought about by lesions on the nerves that connect to the nasociliary branch of the ophthalmic nerve . [ 7 ]
Conversely, parasympathetic stimulation causes contraction of the circular muscle and constriction of the pupil. The mechanism of mydriasis depends on the agent being used. It usually involves either a disruption of the parasympathetic nerve supply to the eye (which normally constricts the pupil) or overactivity of the sympathetic nervous ...
Apraclonidine is useful in this case due to its weak α 1-adrenergic properties. When applied to the denervated (and thus hyper-sensitive) pupillary dilator muscle, a super-normal dilatory response is generated in which the pupil dilates to a degree greater than that which would be seen in a non-denervated muscle.
The tonic pupil may become smaller (miotic) over time which is referred to as "little old Adie's". [5] Testing with low dose (1/8%) pilocarpine may constrict the tonic pupil due to cholinergic denervation supersensitivity. [1] A normal pupil will not constrict with the dilute dose of pilocarpine. [5]