Certain health and ocular considerations may contraindicate pupil dilation. Ocular anatomy, allergies, and certain medications may present a risk in pupil dilation. Optometric physicians carefully evaluate all risk factors prior to pupil dilation. Mydriatic drops are the class of drugs typically used. Chemical names for mydriatics include phenylephrine hydrochloride, hydroxyamphetamine hydrobromide, and tropicamide.
Special circumstances require compounds known as cycloplegics to be used.
Chemical names of the cycloplegic drops are atropine, cyclopentolate, homatropine, and scopolamine. Mydriatic are fast acting compounds and dilation of the pupil occurs in 20 to 45 minutes. Patients with light-colored eyes dilate faster than those with dark eyes. Depending on an individual's sensitivity to the dilating drops, the effects may last 2 to 6 hours. Most people experience mild visual side effects while dilated.