MTHFR and retinoblastoma: Patients with MTHFR mutations who also receive N<sub>2</sub>O during ophthalmic artery chemotherapy (OAC) for retinoblastoma may have a heightened thrombotic risk.<h4>Case presentations</h4>Single-center retrospective review of pediatric patients with advanced retinoblastoma who received OAC and developed choroidal infarcts.