Sometimes, a more detailed look at the retina is required than is possible through a normal-sized pupil. This is often when the patient is experiencing flashes and/or floaters which can indicate an eye condition such as a retinal detachment.
When a more detailed retinal examination is required, it is done by dilating the pupils. Drops are placed into the patient's eyes, which (in 20-25 minutes) make the pupils open up very wide:
Once the eyes are dilated, a more detailed view of the internal structure of the eyes is possible.