Congenital vertical nystagmus; A case report

Although congenital vertical nystagmus is very rare, we treated on 6-year-old girl who had spontaneous eye movements and myopia. Down beat nystagmus was noted on forward gaze, and it increased in amplitude and frequency on downward gaze. The nystagmus disappeared when her eyes were closed in a lighted room and when her eyes were open in a dark room.Eye tracking tests for slow and quick components in the horizontal plane were normal. Optokinetic nystagmus in the horizontal plane was within normal limits. Normal caloric responses were observed. No vertical optokinetic nystagmus was induced. The patient had complete loss of the slow pursuit function in the vertical plane. Therefore, we considered this to be a case of congenital vertical nystagmus due to a disturbance of the slow pursuit system of vertical eye movements.