The ERG is a sensitive and specific predictor of eyes with CRVO that will develop neovascularization of the iris (NVI) and subsequent neovascular glaucoma. A simple 10 minute test — the 30 Hz flicker ERG — taken the first time the patient presents with symptoms of CRVO, can predict with 93% accuracy whether the patient will develop NVI. Studies have shown that the ERG is much better at predicting outcomes in this disease than is fluorescein angiography.