A 15-year-old girl with a ventriculoperitoneal shunt for congenital hydrocephalus presented with bilateral visual loss and disc edema. Although a CT scan showed no change in ventricular size, subsequent evaluation revealed elevated intracranial pressure and shunt malfunction. Initial visual loss was secondary to chronic papilledema. The rapid reduction of longstanding elevated intracranial pressure may have contributed to worsening of visual function after shunt revision. Subsequent optic nerve sheath fenestration did not improve visual function. In patients with treated hydrocephalus and symptoms of signs of raised intracranial pressure, shunt malfunction should be suspected even if neuro-imaging proves unremarkable.