Dilating eyedrops can keep eyes dilated for up to several hours, according to the American Academy of Ophthalmology. The time varies depending on the individual, their eye color and the number of drops administered.
Dilating eyedrops are used to help improve the efficacy of an eye exam by allowing the doctor to examine the eye structures, including the retina and the optic nerve, notes About.com.
People with light-colored eyes can expect to dilate faster because they are more sensitive to the eyedrops. Since the effects of dilated eyes include blurry vision and sensitivity to light, doctors encourage dilated patients to temporarily wear sunglasses to reduce glare.