Arteriovenous malformations (AVMs) of the orbit are rare and are thought to be congenital. They can grow slowly or in a delayed fashion after a prolonged period of quiescence if there is a hemodynamic balance between the in-flow and the out-flow vessels. However, once the balance is destroyed, orbital AVMs may cause acute visual deterioration. We report a 17-year-old male with orbital AVM, and discuss the mechanism and the management of acute visual deterioration in this setting. Angiography revealed an orbital AVM with obvious drainage obstruction and serious orbital congestion, due to the disruption of the balance. He had no vision improvement although treated successfully with radical transarterial embolization. The worsening of drainage obstruction could alter the hemodynamic flow and lead to acute visual deterioration. Early and exact diagnosis and complete transarterial embolization therapy are important before the hemodynamic imbalance.