In a 12-member, 3-generation kindred with conjoint inheritance of G1691Afactor V Leiden (FVL) and G20210A prothrombin gene (PTG) mutations, identified through a proband with amaurosis fugax and his father with nonarteritic ischemic optic neuropathy (NAION), the authors' hypothesis was that ocular thrombosis was a diagnostic window to familial thrombophilia-thrombosis.