Causes and treatment of congenital eccentric nystagmus.

THE cause of congenital nystagmus has been considered to be as obscure as the disorder is resistant to treatment. This paper contains little hint of value regarding the former but it is believed that it does contain some for the latter. Nystagmus may be divided into the following groups: (1) Visual or fixation nystagmus. (2) Oculomotor or gaze nystagmus. (3) Vestibular nystagmus. The movements of the first are oscillatory, and may be replaced by rhythmic jerks when the eyes are rotated to right or left. The movements of the second group are mainly rhythmic with a fast component in the direction of gaze. They are gaze-determined. The movements of the third group are also rhythmic, but the fast component may be towards one side regardless of the direction of gaze. The nystagmus is side-determined, either towards or away from the affected labyrinth or its connections; the movements are horizontal and rotatory combined, whereas those of the second group are purely horizontal except for a slight rotatory movement at times of the adducted eye.