A 6-year-old girl with neurofibromatosis type 1 (NF1) is brought to the pediatric clinic with complaints of progressive vision problems and headaches over the past 3 months. Her parents report that she frequently trips over objects and complains of double vision. On physical examination, she has proptosis of the right eye and decreased visual acuity. An MRI of the brain shows a tumor along the right optic nerve. Which of the following is the most likely diagnosis?
