Pupil dilators dilate the pupil uniformly to explore the interior of the eye as well as to perform internal eye surgery, such as small pupil cataract ultrasonoemulsification surgery. Clinical dilation of the pupil with a dilating agent allows the physician to observe intraocular structures, and for some peripheral structures such as the suspensory ligament of the lens, the use of a pupil dilator allows for more visualization. Small pupil cataract is a special kind of complex cataract, cataract removal surgery in small pupil, operating space is small, the operation is difficult, relatively high risk. Therefore, physicians can use a pupil dilator, which not only effectively dilates the pupil, but also protects the pupil rim and reduces iris damage. In conclusion, the pupil dilator is a commonly used medical device in ophthalmologic examination and surgery.