seidel sign seidel sign seidel's sign (also called seidel's scotoma) is a sickle-shaped scotoma that is a superior or inferior extension of the blind spot. it occurs in some patients with glaucoma. seidel signa visual description of the sites of different types of scotomas on the retina.seidels sign is marked with orangedifferential diagnosisglaucoma history in 1914, german ophthalmologist erich seidel first described the glaucomatous visual field defect, seidel's scotoma.