Unevenly dilated pupils?

Last night I was washing my face and saw that my one pupils was quite small compared to the other one. It was back to normal later but today, a whole 24 hours later, they were different sizes again. I went to the he doctors last week and my eye other than being near sighted where fine. I was wondering what might be cause he uneven dilation of my pupils? I wear glasses and contact lens if that has anything to do with it.