Pathologic nystagmus: a classification based on electro-oculographic recordings.

The widespread availability of eye movement recording systems has added a new dimension to our ability to accurately describe nystagmus. Electrooculography (EOG) is the simplest and most readily available system. With EOG the effect of loss of fixation (either with eyes closed, or eyes open in darkness) can be accurately assessed and quantitative evaluation of nystagmus speed, frequency and amplitude is easily made. Of equal importance, it provides a permanent record that can be compared with nystagmus recorded in other patients. By comparing clinical observation with paper recordings, both students and experienced clinicians can become more efficient in recognizing different varieties of nystagmus.