Accurate eye movement recordings of sixty-five subjects with congenital nystagmus (CN) provides a firm foundation for the classification of the many types of waveforms observed and results in objective definitions based on measurable quantities rather than subjective clinical impressions. The careful scrutiny of these records along with the utilization of laser-target cinematography have yielded insights into the mechanism of this ocular motor instability. Prolongation of target foveation emerges as the dominant factor in many of the resultant waveforms. This enhances the visual acuity of the subject with CN. An additional observation, related to fixation bias reversals of the CN subject, may be a physiological indicator of foveal function.