1. A method of treating mydriasis in a human patient due to said patient having received one or more of tropicamide, phenylephrine, or a pharmaceutically acceptable salt thereof, comprising administering to an eye of the human patient in need thereof a dosage of phentolamine mesylate to thereby treat the mydriasis, wherein the dosage is topically administered to the patient's eye as one eye drop of a 1% (w/w) phentolamine mesylate solution, and at two hours after the dosage of phentolamine mesylate is administered to the patient's eye there is at least a 30% reduction in pupil diameter in said eye of the patient measured under photopic conditions.