- Pupil dilation. The risks of pupil dilation include fatigue of the neck; pain in the neck; pressure under the chin; sweating; photophobia; acute angle-closure lasting for less than 30 minutes, due to the dilating drops; conjunctival injection (red eye), due to the dilating drops; impaired near vision for less than 24 hours, due to dilating drops; burning for less than 5 minutes, due to the dilating drops; or anesthesia of the eye for less than 2 hours, due to the dilating drops. None of these are permanent or substantial losses. Rest and time will resolve the complication.