Ocular movement during reading in patients with congenital nystagmus.

When a healthy person reads sentences arranged horizontally, the eye movement pattern is a series of regular saccades and rest periods. However, eye movements while patients with oculomotor disturbances are reading remain to be defined. In this study, 4 patients with congenital nystagmus (CN) were studied. Coordinated movements of eye and head are also studied by a new apparatus with terrestrial magnetism sensor. While subjects were reading, an eye movement pattern was superimposed by the CN waveform and showed few rest periods. Eye velocity of less than 4 degrees/s was noted in almost every cycle of the eye movements while the patients with CN were reading. When they were requested to read sentences and simultaneously rotate their head naturally, the head movements had the effect of cancelling the eye instability. This finding may be interpreted as a kind of "eye-head coordination".