How old is your child? boy or girl?
In most instances of leukocoria detected by a photograph, it is due to the angle of the eye as it relates to the picture being taken. However, an evaluation by a pediatric ophthalmologist is indicated as true leukocoria could be due to a number of possibilities. Among these are conditions like cataracts, uveitis (inflammation inside the eye) and a number of diseases of the retina including tumors(ex- Retinoblastoma, Coat's disease, Retinal dysplasia). These possible diagnoses affect the vision significantly and in a number of cases the child displays difficulty seeing prior to the leukocoria.
It is especially important to have him evaluated if there is a family history of genetic conditions affecting the eyes. Still, even without a family history, an evaluation is indicated. This will rule out any pathology and, if nothing else, offer peace of mind. I would like to emphasize that, in most instances, there is no pathology found on exam.
Good luck to you and your son as you continue to evaluate his leukocoria...