Test, pupil dilation: Opening the pupil wide enables an eye care professional to see more of the retina, the light-sensitive layer of tissue at the back of the eye. Dilating (widening) the pupil permits the retina to be examined for signs of disease. To do this, drops are placed into the eye to dilate the pupil. After dilation, vision may remain blurred and the patient may be bothered by the brightness of the sun for several hours.
