dilation, pupil

dilation, pupil 1 A type of eye examination that enables an eye-care professional to see more of the retina, the light-sensitive layer of tissue at the back of the eye. Dilating the pupil permits the retina to be examined for signs of disease. To dilate the pupil, drops are placed into the eye. 2 A normal response of the iris to a decrease in light exposure. 3 An abnormal widening of the pupil in response to brain injury.