Fig 1 shows pupil constriction and dilation. Pupil size is controlled by two muscles:

  • The sphincter of the iris: parasympathetic stimulation produces pupil constriction (miosis)
  • The radial muscle of the iris: sympathetic stimulation produces pupil dilation (mydriasis) (α1)

Question: What are the effects of the drugs atropine and adrenaline on the eye?

Answer

Fig 1 Top: Pupil constriction: miosis Bottom: Pupil dilatation: mydriasis

Fig 1 shows pupil constriction and dilation. Pupil size is controlled by two muscles:

  • The sphincter of the iris: parasympathetic stimulation produces pupil constriction (miosis)
  • The radial muscle of the iris: sympathetic stimulation produces pupil dilation (mydriasis) (α1)

Question: What are the effects of the drugs atropine and adrenaline on the eye?

Answer: Both cause pupil dilation and blurred vision, by parasympathetic block (atropine) and sympathetic stimulation (adrenaline) (Fig 2).

Fig 2 Pupil dilatation caused by atropine or adrenaline

Fig 1 shows pupil constriction and dilation. Pupil size is controlled by two muscles:

  • The sphincter of the iris: parasympathetic stimulation produces pupil constriction (miosis)
  • The radial muscle of the iris: sympathetic stimulation produces pupil dilation (mydriasis) (α1)

Question: What are the effects of the drugs atropine and adrenaline on the eye?

Answer: Both cause pupil dilation and blurred vision, by parasympathetic block (atropine) and sympathetic stimulation (adrenaline) (Fig 2).

Fig 1 Top: Pupil constriction: miosis Bottom: Pupil dilatation: mydriasis