| ICD9 = | DiseasesDB = 8603 | OMIM = 159420 | OMIM_mult = | Image = Dilated pupils 2006.jpg | Caption = Pupil dilated for examination by optometrist. }} Mydriasis's an excessive dilation of the pupil due to disease, trauma or the use of drugs. Normally, the pupil dilates in the dark and constricts in the light to improve vividity at night and to protect the retina from sunlight damage during the day. A mydriatic pupil will remain excessively large even in a bright environment and's sometimes c… (More on Mydriasis)