"The subject of ring scotoma though not even mentioned in the majority of our text books is one of great interest, and its careful study, together with a faithful record of cases, might not improbably add much to our present knowledge . . . few attempts have been made to deal exhaustively with the subject" (Hancock1).
These lines, written thirty-three years ago, are still justified. The conditions in which Hancock observed ring scotoma have not increased much. He named retinitis pigmentosa, retinitis, choroiditis, retinochoroiditis, lesions of the optic nerve with or without optic neuritis, glaucoma, idiopathic night blindness and myopia. Since then only few additional causes have been described. These are : blinding by diffuse lights, especially in aviators (Zade2); abnormal functional fatigability (Gelb and Goldstein3); migraine (Zentmayer4) ; accidents (A. Fuchs5); callus from fracture (Lillie and Adson6), and tobacco (Krimsky7). The encyclopedia of von Schieck and Bruckner