Analysis of the Effects of Atropine and Pilocarpine on the Pupil
Nov 25, 2025
Source: Cainiu Health
Dr. Wang Lei
Introduction
The effects of atropine and pilocarpine on the pupil include changes in pupil size, alterations in pupillary light reflex, impact on accommodation function, differences in mechanisms of action, and distinct clinical applications. The two drugs have opposite effects and both require strict control. If eye pain, sudden vision loss, or allergic reactions occur after administration, prompt medical attention is recommended. Atropine blocks the M receptors in the pupillary sphincter muscle, causing pupil dilation.
The effects of atropine and pilocarpine on the pupil include changes in pupil size, alterations in pupillary light reflex, impact on accommodation function, differences in mechanisms of action, and distinct clinical applications. The two agents have opposing effects and both require strict control. If eye pain, sudden vision loss, or allergic reactions occur after use, prompt medical attention is recommended.
1. Changes in pupil size: Atropine blocks M receptors in the pupillary sphincter muscle, causing mydriasis (pupil dilation); pilocarpine activates these receptors, resulting in miosis (pupil constriction). Their actions are directly opposite and both can rapidly alter pupil morphology.
2. Changes in pupillary light reflex: Atropine causes sluggish or absent pupillary light reflex due to loss of sphincter muscle contraction; pilocarpine does not inhibit the light reflex—after pupil constriction, the pupils can still adjust normally in response to changes in light intensity.
3. Impact on accommodation function: Atropine induces cycloplegia (paralysis of accommodation), leading to blurred vision, especially for near objects; pilocarpine enhances accommodative function, which may improve mild myopic blurring and relieve discomfort associated with eye fatigue.
4. Differences in mechanism of action: Atropine acts as a cholinergic receptor antagonist, inhibiting parasympathetic nervous system activity; pilocarpine is a cholinergic receptor agonist that enhances parasympathetic effects. This opposing mechanism results in contrasting physiological effects.
5. Differences in clinical applications: Atropine is used for pupillary dilation during eye examinations, refraction testing, or to relieve ciliary spasm in uveitis; pilocarpine is primarily used to treat glaucoma by reducing intraocular pressure through miosis, and may also assist in restoring normal pupil size after dilation.
Medication must be used strictly according to medical instructions regarding dosage and duration; self-medication should be avoided. After administration, exposure to bright light should be minimized, and sunglasses are recommended when outdoors. If combination therapy is needed, sufficient time intervals between drugs should be maintained, and close monitoring of ocular responses is essential to ensure safety.
