A:
You should take her to see an ophthalmologist who treats children.
In most cases, having pupils of different sizes is not serious, as long as nothing else is obviously wrong with the eyes. This applies to adults and children.
In infants, high pressure in the eye can cause a large pupil. Although rare, a tumor inside the eye could cause this.
Pupil size is controlled by a complex set of checks and balances involving at least two different nervous systems. The possibilities for different size (asymmetric) pupils are very complex. The causes range from medications to paralysis of the nerves.
