Optic nerve drusen are abnormal globular collections of protein and calcium salts in the optic nerve. They are often present in both eyes, but sometimes occur only in one eye. Rarely, peripheral vision loss may occur slowly, but is so minimal that it is not noticeable. Visual field exams may be performed to monitor for decreased peripheral vision in older children. Another rare complication from optic nerve drusen is choroidal neovascular membrane. This is a collection ofabnormal blood vessels which grow beneath the retina near the optic nerve. Yearly dilated eye examinations are recommended to monitor for any changes.