What could cause sudden onset amblyopia in a child? 7 years old, just last year had perfect vision now -3.75 in one eye. normal? see neurologist?

Ped. ophthalmologist: If you are certain that this eye saw 20/20 without correction a year ago then this might be cause for alarm. More likely is the possibility that vision measured in a pediatrician's office might have missed the child squinting or somehow using the other eye during the exam. Many things are possible including cataract, diabetes, progressive myopia, etc. See a pediatric ophthalmologist to begin with.