As Mark said, eye dilation changes depending on the amount of light.

Also... I had my eyes tested this week as well and they dilated my pupils and it took just over 2 days for them to start behaving normally again.

The 2nd day the right one was fine and reactive to light, but the left one was still very dilated... very strange to see when I looked in the mirror... I felt a bit panicky at first, just because of having a head injury not that long ago, but then remembered my eye exam and relaxed.

They are both normal and reactive again.
Starr