Mydriatics: Drugs Used to Enlarge the Pupil

Fig 1: Dilated Pupils

Cyclopentolate 1%, Tropicamide 0.5%, Tropicamide 1%, Phenylephrine 2.5% Phenylephrine 10% can be used to dilate the pupils, but tropicamide (0.5% for children, 1% for adults) is best for diagnostic purposes, dilating the pupil for two to four hours by blocking the parasympathetic terminals in the pupillary constrictor muscle. Cyclopentolate works in a similar manner but lasts for six to eight hours.

Fig 2: Pupillary Constrictor Muscle

Phenylephrine drops dilate the pupil by stimulating the sympathetic system. They should be used with caution both in children and in adults with ischaemic heart disease because they can induce hypertension, exacerbate angina or induce arrhythmias.

Source: Fig1, Fig 2,