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.

A subject with a medial rectus paresis secondary to a partial third nerve palsy was forced to use the affected eye for six days while the good eye was constantly patched. Saccadic eye movements were carefully measured each day; the grain increased, with a time constant of 0.85 day. The patch was then switched to the paretic eye and the gain decreased, with a time constant of 0.85 day. The patch was then switched to the paretic eye and the gain decreased, with a time constant of 1.54 days. This demonstrated central nervous system plasticity of the pulse and step of neural activity responsible for the generation of saccades in the adult human. In addition to gain changes, postsaccadic drift velocity and saccadic velocity/amplitude relationship alterations during the patching are reported. A major conclusion that can be drawn from analysis fo these data is that the gain changing is accomplished by pulse width changes rather than pulse height (firing frequency), which was not markedly altered.

The results of quantitative infrared horizontal eye movement recordings in 8 patients with progressive supranuclear palsy are presented. Some of the patients had total paralysis of vertical movements, but none had completely lost the ability to perform horizontal eye movements. All patients had a defect in ocular fixation previously undescribed in this condition: the universal presence of square-wave jerks. Analysis of refixation saccades demonstrated hypometria, slow velocity/amplitude relationships, and profound prolongation of duration. The pursuit abnormality, characterized clinically by "cogwheel" eye movements, represented the inability to match eye velocity to target velocity. The ratio of peak eye velocity to peak target velocity (pursuit gain) was 0.2 to 0.5. Defects in the vestibuloocular reflex included inability to increase the gain of the reflex (ratio of peak eye velocity to head velocity) during viewing of a visible, stationary target and failure to suppress the reflex when viewing a target rotating with the head.

In this study we recorded eye movements during reading tasks for five dyslexic children and two controls. The subjects had vertical as well as horizontal eye position monitored with an infrared recording technique and performed a symbol-simulated reading task. We demonstrated the importance of both the symbol simulation and the vertical monitoring in evaluating the eye-movement patterns in dyslexics. Without the symbols, motor and comprehension defects cannot be distinguished. Without vertical eye position information, the horizontal eye-movement pattern is not properly interpretable.

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