A 14-year-old girl had headaches and sudden loss of vision as a result of total retinal detachment in association with the morning glory optic nerve anomaly. Metrizamide cisternography with contrast dye introduced into the subarachnoid space disclosed migration of metrizamide with radiographic enhancement in the subretinal space. The demonstration of an abnormal communication between the subarachnoid and subretinal spaces suggested that the subretinal fluid is of cranial origin. The patient underwent surgical removal of a window of dura from the optic nerve sheath. This resulted in retinal reattachment and improvement of visual acuity to 20/200. The retina was still attached after a 15-month follow-up period.