Pupil dilation is characterized by the expansion of the pupil in the eye. It may occur as a natural reaction to low levels of light, as a result of injury or trauma, or as a side effect of medication or drugs. 

Physicians or ophthalmologists may achieve pupil dilation artificially with medicated drops to enable them to conduct a full retina examination. Eye exams are a valuable method of diagnosing a variety of conditions in the early stages, include diabetes, glaucoma, high blood pressure, retinal detachment, and vasculitis. 

Medications used for pupil dilation include mydriatics and cycloplegics and ophthalmological non-steroidal anti-inflammatories.