(A–G) Disc photographs of cases 1–7 respectively. (H) (case 7) Left inferior disc coloboma. (I) (case 4) B-scan ultrasound showing peripapillary optic disc coloboma and only one optic nerve. (J–M) Disc photographs of cases 8–11 respectively. (N) (case 11) Arteriovenous phase, and (O) late venous phase fundus fluorescein angiography showing absence of dual retinal blood vessels.