This cavity in the inferior portion of the optic disc is a congenital anomaly, perhaps a mild form of optic disc coloboma. Because the cavity has no retinal ganglion cell axons, the patient will manifest a corresponding nerve fiber bundle visual field defect, which may be the abnormality that brings this condition to medical attention. Often confused with glaucoma, it may generate fruitless intraocular pressure-lowering treatment. The cavity and the visual field are stationary. There may be an associated serous detachment of the macula.