Congenital hereditary vertical nystagmus.

Duke-Elder (1949) states that congenital nystagmus varies considerably in extent, direction, and rapidity of the movements. In most cases it affects both eyes equally, but in a few instances it is uniocular. Typically the movements are pendular in type, horizontal in direction, and do not alter on lateral deviation, although they may then become jerky in type. Sometimes the movement is coarser to one side than the other, in which case the head is habitually turned to place the eyes in the position at which the nystagnus is least. In 1911, Nettleship reviewed nine pedigrees of congenital hereditary nystagmus and to this he added four more which he had examined personally. Hemmes (1926) published a pedigree and reviewed all published pedigrees up to 1924, 38 in all. Since then Yawger (1917), Cox (1936), Glover (1937), Waggoner and Boyd (1942), and Rucker (1946) have added their contributions. A careful study of the published reports has shown, with two exceptions, that the nystagmus has been bilateral and horizontal in all cases. Posey (1902) described a native boy, aged 8 years, who had bilateral vertical nystagmus. The time of onset was not known, but oscillations of the head, of a rotary type, began at 5 years. Three siblings were normal and There was no family history of abnormal eye movements. Walsh (1947) states that the nystagmus is usually horizontal, although torsional nystagnus has been observed by Ohm (1938). It would appear, therefore, that congenital nystagmus of the vertical type is rare. This condition is of great interest to the geneticist and it is for this reason that these cases are recorded. The family described here is of pure Italian extraction and the nystagmus involves five cases spread over three generations; three males and two females. The diagrammatic pedigree is set out in the Appendix. Twelve members of the family have been examined and their blood groups and eye colours, etc., are recorded also in the Appendix. There is no known consanguinity in -he matings. Case Reports